Units
Translation components API.
See the Weblate's Web API documentation for detailed description of the API.
GET /api/translations/documentation/articlesvm-design_index/en/units/?format=api
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100, "id": 368027, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=4e52269c601e45f7", "url": "https://translate-dev.freebsd.org/api/units/368027/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:47.072659Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "Pre-Faulting and Zeroing Optimizations" ], "previous_source": "", "target": [ "Pre-Faulting and Zeroing Optimizations" ], "id_hash": -7199560516843032198, "content_hash": -7199560516843032198, "location": "documentation/content/en/articles/vm-design/_index.adoc:249", "context": "", "note": "type: Title ==", "flags": "no-wrap", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 54, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 4, "source_unit": "https://translate-dev.freebsd.org/api/units/368045/?format=api", "priority": 100, "id": 368045, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=1c1605dad6a4b17a", "url": "https://translate-dev.freebsd.org/api/units/368045/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:47.259936Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "Page Table Optimizations" ], "previous_source": "", "target": [ "Page Table Optimizations" ], "id_hash": 7381999408203105810, "content_hash": 7381999408203105810, "location": "documentation/content/en/articles/vm-design/_index.adoc:270", "context": "", "note": "type: Title ==", "flags": "no-wrap", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 57, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 3, "source_unit": "https://translate-dev.freebsd.org/api/units/368051/?format=api", "priority": 100, "id": 368051, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=e6722159aa170612", "url": "https://translate-dev.freebsd.org/api/units/368051/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:47.322822Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "Page Coloring" ], "previous_source": "", "target": [ "Page Coloring" ], "id_hash": 5361117431676146431, "content_hash": 5361117431676146431, "location": "documentation/content/en/articles/vm-design/_index.adoc:287", "context": "", "note": "type: Title ==", "flags": "no-wrap", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 60, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 2, "source_unit": "https://translate-dev.freebsd.org/api/units/368057/?format=api", "priority": 100, "id": 368057, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=ca6683e6523612ff", "url": "https://translate-dev.freebsd.org/api/units/368057/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:47.387725Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "Conclusion" ], "previous_source": "", "target": [ "Conclusion" ], "id_hash": -438954553492005104, "content_hash": -438954553492005104, "location": "documentation/content/en/articles/vm-design/_index.adoc:306", "context": "", "note": "type: Title ==", "flags": "no-wrap", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 63, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 1, "source_unit": "https://translate-dev.freebsd.org/api/units/368063/?format=api", "priority": 100, "id": 368063, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=79e88528c6919f10", "url": "https://translate-dev.freebsd.org/api/units/368063/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:47.453896Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "Bonus QA session by Allen Briggs" ], "previous_source": "", "target": [ "Bonus QA session by Allen Briggs" ], "id_hash": -3193954519288190759, "content_hash": -3193954519288190759, "location": "documentation/content/en/articles/vm-design/_index.adoc:313", "context": "", "note": "type: Title ==", "flags": "no-wrap", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 65, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 6, "source_unit": "https://translate-dev.freebsd.org/api/units/368067/?format=api", "priority": 100, "id": 368067, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=53accb497912e8d9", "url": "https://translate-dev.freebsd.org/api/units/368067/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:47.493724Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "What is the interleaving algorithm that you refer to in your listing of the ills of the FreeBSD 3.X swap arrangements?" ], "previous_source": "", "target": [ "What is the interleaving algorithm that you refer to in your listing of the ills of the FreeBSD 3.X swap arrangements?" ], "id_hash": -648622040058245068, "content_hash": -648622040058245068, "location": "documentation/content/en/articles/vm-design/_index.adoc:315", "context": "", "note": "type: Title ===", "flags": "no-wrap", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 66, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 21, "source_unit": "https://translate-dev.freebsd.org/api/units/368069/?format=api", "priority": 100, "id": 368069, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=76ffa1b0ecd6d034", "url": "https://translate-dev.freebsd.org/api/units/368069/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:47.512352Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "A B C D A B C D A B C D A B C D\n" ], "previous_source": "", "target": [ "A B C D A B C D A B C D A B C D\n" ], "id_hash": 922062017217951916, "content_hash": 922062017217951916, "location": "documentation/content/en/articles/vm-design/_index.adoc:324", "context": "", "note": "type: delimited block . 4", "flags": "no-wrap", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 68, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 16, "source_unit": "https://translate-dev.freebsd.org/api/units/368073/?format=api", "priority": 100, "id": 368073, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=8ccbd284f527f8ac", "url": "https://translate-dev.freebsd.org/api/units/368073/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:47.550678Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "Why do we interleave our swap space instead of just tack swap areas onto the end and do something fancier? It is a whole lot easier to allocate linear swaths of an address space and have the result automatically be interleaved across multiple disks than it is to try to put that sophistication elsewhere." ], "previous_source": "", "target": [ "Why do we interleave our swap space instead of just tack swap areas onto the end and do something fancier? It is a whole lot easier to allocate linear swaths of an address space and have the result automatically be interleaved across multiple disks than it is to try to put that sophistication elsewhere." ], "id_hash": -5189863536442483307, "content_hash": -5189863536442483307, "location": "documentation/content/en/articles/vm-design/_index.adoc:333", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 70, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 54, "source_unit": "https://translate-dev.freebsd.org/api/units/368077/?format=api", "priority": 100, "id": 368077, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=37f9e69c5597dd95", "url": "https://translate-dev.freebsd.org/api/units/368077/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:47.591041Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "How is the separation of clean and dirty (inactive) pages related to the situation where you see low cache queue counts and high active queue counts in systat -vm? Do the systat stats roll the active and dirty pages together for the active queue count?" ], "previous_source": "", "target": [ "How is the separation of clean and dirty (inactive) pages related to the situation where you see low cache queue counts and high active queue counts in systat -vm? Do the systat stats roll the active and dirty pages together for the active queue count?" ], "id_hash": 3353279667003563824, "content_hash": 3353279667003563824, "location": "documentation/content/en/articles/vm-design/_index.adoc:344", "context": "", "note": "type: Title ===", "flags": "no-wrap", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 73, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 45, "source_unit": "https://translate-dev.freebsd.org/api/units/368083/?format=api", "priority": 100, "id": 368083, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=ae893e1738499f30", "url": "https://translate-dev.freebsd.org/api/units/368083/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:48.085686Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "What this means is that FreeBSD will not try very hard to separate out dirty pages (inactive queue) from clean pages (cache queue) when the system is not being stressed, nor will it try to deactivate pages (active queue -> inactive queue) when the system is not being stressed, even if they are not being used." ], "previous_source": "", "target": [ "What this means is that FreeBSD will not try very hard to separate out dirty pages (inactive queue) from clean pages (cache queue) when the system is not being stressed, nor will it try to deactivate pages (active queue -> inactive queue) when the system is not being stressed, even if they are not being used." ], "id_hash": -5926730276734892911, "content_hash": -5926730276734892911, "location": "documentation/content/en/articles/vm-design/_index.adoc:351", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 75, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 56, "source_unit": "https://translate-dev.freebsd.org/api/units/368087/?format=api", "priority": 100, "id": 368087, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=2dc00636e7aa0491", "url": "https://translate-dev.freebsd.org/api/units/368087/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:48.176999Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "In man:ls[1] the / vmstat 1 example, would not some of the page faults be data page faults (COW from executable file to private page)? I.e., I would expect the page faults to be some zero-fill and some program data. Or are you implying that FreeBSD does do pre-COW for the program data?" ], "previous_source": "", "target": [ "In man:ls[1] the / vmstat 1 example, would not some of the page faults be data page faults (COW from executable file to private page)? I.e., I would expect the page faults to be some zero-fill and some program data. Or are you implying that FreeBSD does do pre-COW for the program data?" ], "id_hash": 7433035198401274017, "content_hash": 7433035198401274017, "location": "documentation/content/en/articles/vm-design/_index.adoc:352", "context": "", "note": "type: Title ===", "flags": "no-wrap", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 76, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 53, "source_unit": "https://translate-dev.freebsd.org/api/units/368089/?format=api", "priority": 100, "id": 368089, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=e72772218baee0a1", "url": "https://translate-dev.freebsd.org/api/units/368089/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:48.197787Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "In your section on page table optimizations, can you give a little more detail about pv_entry and vm_page (or should vm_page be vm_pmap-as in 4.4, cf. pp. 180-181 of McKusick, Bostic, Karel, Quarterman)? Specifically, what kind of operation/reaction would require scanning the mappings?" ], "previous_source": "", "target": [ "In your section on page table optimizations, can you give a little more detail about pv_entry and vm_page (or should vm_page be vm_pmap-as in 4.4, cf. pp. 180-181 of McKusick, Bostic, Karel, Quarterman)? Specifically, what kind of operation/reaction would require scanning the mappings?" ], "id_hash": -131807252796287441, "content_hash": -131807252796287441, "location": "documentation/content/en/articles/vm-design/_index.adoc:359", "context": "", "note": "type: Title ===", "flags": "no-wrap", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 78, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 43, "source_unit": "https://translate-dev.freebsd.org/api/units/368093/?format=api", "priority": 100, "id": 368093, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=7e2bba007e41d62f", "url": "https://translate-dev.freebsd.org/api/units/368093/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:48.238197Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "Finally, in the page coloring section, it might help to have a little more description of what you mean here. I did not quite follow it." ], "previous_source": "", "target": [ "Finally, in the page coloring section, it might help to have a little more description of what you mean here. I did not quite follow it." ], "id_hash": 2004629771682149064, "content_hash": 2004629771682149064, "location": "documentation/content/en/articles/vm-design/_index.adoc:384", "context": "", "note": "type: Title ===", "flags": "no-wrap", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 85, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 26, "source_unit": "https://translate-dev.freebsd.org/api/units/368107/?format=api", "priority": 100, "id": 368107, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=9bd1e028074972c8", "url": "https://translate-dev.freebsd.org/api/units/368107/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-02-21T23:17:48.377585Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "The title is really just a fancy way of saying that I am going to attempt to describe the whole VM enchilada, hopefully in a way that everyone can follow. For the last year I have concentrated on a number of major kernel subsystems within FreeBSD, with the VM and Swap subsystems being the most interesting and NFS being \"a necessary chore\". I rewrote only small portions of the code. In the VM arena the only major rewrite I have done is to the swap subsystem. Most of my work was cleanup and maintenance, with only moderate code rewriting and no major algorithmic adjustments within the VM subsystem. The bulk of the VM subsystem's theoretical base remains unchanged and a lot of the credit for the modernization effort in the last few years belongs to John Dyson and David Greenman. Not being a historian like Kirk I will not attempt to tag all the various features with peoples names, since I will invariably get it wrong." ], "previous_source": "", "target": [ "The title is really just a fancy way of saying that I am going to attempt to describe the whole VM enchilada, hopefully in a way that everyone can follow. For the last year I have concentrated on a number of major kernel subsystems within FreeBSD, with the VM and Swap subsystems being the most interesting and NFS being \"a necessary chore\". I rewrote only small portions of the code. In the VM arena the only major rewrite I have done is to the swap subsystem. Most of my work was cleanup and maintenance, with only moderate code rewriting and no major algorithmic adjustments within the VM subsystem. The bulk of the VM subsystem's theoretical base remains unchanged and a lot of the credit for the modernization effort in the last few years belongs to John Dyson and David Greenman. Not being a historian like Kirk I will not attempt to tag all the various features with peoples names, since I will invariably get it wrong." ], "id_hash": 7312304718250146262, "content_hash": 7312304718250146262, "location": "documentation/content/en/articles/vm-design/_index.adoc:53", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 5, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 166, "source_unit": "https://translate-dev.freebsd.org/api/units/615365/?format=api", "priority": 100, "id": 615365, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=e57a866624b679d6", "url": "https://translate-dev.freebsd.org/api/units/615365/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:30.055683Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "Before moving along to the actual design let's spend a little time on the necessity of maintaining and modernizing any long-living codebase. In the programming world, algorithms tend to be more important than code and it is precisely due to BSD's academic roots that a great deal of attention was paid to algorithm design from the beginning. More attention paid to the design generally leads to a clean and flexible codebase that can be fairly easily modified, extended, or replaced over time. While BSD is considered an \"old\" operating system by some people, those of us who work on it tend to view it more as a \"mature\" codebase which has various components modified, extended, or replaced with modern code. It has evolved, and FreeBSD is at the bleeding edge no matter how old some of the code might be. This is an important distinction to make and one that is unfortunately lost to many people. The biggest error a programmer can make is to not learn from history, and this is precisely the error that many other modern operating systems have made. Windows NT(R) is the best example of this, and the consequences have been dire. Linux also makes this mistake to some degree-enough that we BSD folk can make small jokes about it every once in a while, anyway. Linux's problem is simply one of a lack of experience and history to compare ideas against, a problem that is easily and rapidly being addressed by the Linux community in the same way it has been addressed in the BSD community-by continuous code development. The Windows NT(R) folk, on the other hand, repeatedly make the same mistakes solved by UNIX(R) decades ago and then spend years fixing them. Over and over again. They have a severe case of \"not designed here\" and \"we are always right because our marketing department says so\". I have little tolerance for anyone who cannot learn from history." ], "previous_source": "", "target": [ "Before moving along to the actual design let's spend a little time on the necessity of maintaining and modernizing any long-living codebase. In the programming world, algorithms tend to be more important than code and it is precisely due to BSD's academic roots that a great deal of attention was paid to algorithm design from the beginning. More attention paid to the design generally leads to a clean and flexible codebase that can be fairly easily modified, extended, or replaced over time. While BSD is considered an \"old\" operating system by some people, those of us who work on it tend to view it more as a \"mature\" codebase which has various components modified, extended, or replaced with modern code. It has evolved, and FreeBSD is at the bleeding edge no matter how old some of the code might be. This is an important distinction to make and one that is unfortunately lost to many people. The biggest error a programmer can make is to not learn from history, and this is precisely the error that many other modern operating systems have made. Windows NT(R) is the best example of this, and the consequences have been dire. Linux also makes this mistake to some degree-enough that we BSD folk can make small jokes about it every once in a while, anyway. Linux's problem is simply one of a lack of experience and history to compare ideas against, a problem that is easily and rapidly being addressed by the Linux community in the same way it has been addressed in the BSD community-by continuous code development. The Windows NT(R) folk, on the other hand, repeatedly make the same mistakes solved by UNIX(R) decades ago and then spend years fixing them. Over and over again. They have a severe case of \"not designed here\" and \"we are always right because our marketing department says so\". I have little tolerance for anyone who cannot learn from history." ], "id_hash": 3503886788887829682, "content_hash": 3503886788887829682, "location": "documentation/content/en/articles/vm-design/_index.adoc:75", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 8, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 324, "source_unit": "https://translate-dev.freebsd.org/api/units/615367/?format=api", "priority": 100, "id": 615367, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=b0a04e7858d7dcb2", "url": "https://translate-dev.freebsd.org/api/units/615367/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:30.438853Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "Much of the apparent complexity of the FreeBSD design, especially in the VM/Swap subsystem, is a direct result of having to solve serious performance issues that occur under various conditions. These issues are not due to bad algorithmic design but instead rise from environmental factors. In any direct comparison between platforms, these issues become most apparent when system resources begin to get stressed. As I describe FreeBSD's VM/Swap subsystem the reader should always keep two points in mind:" ], "previous_source": "", "target": [ "Much of the apparent complexity of the FreeBSD design, especially in the VM/Swap subsystem, is a direct result of having to solve serious performance issues that occur under various conditions. These issues are not due to bad algorithmic design but instead rise from environmental factors. In any direct comparison between platforms, these issues become most apparent when system resources begin to get stressed. As I describe FreeBSD's VM/Swap subsystem the reader should always keep two points in mind:" ], "id_hash": -5877286600379949665, "content_hash": -5877286600379949665, "location": "documentation/content/en/articles/vm-design/_index.adoc:80", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 9, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 78, "source_unit": "https://translate-dev.freebsd.org/api/units/615369/?format=api", "priority": 100, "id": 615369, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=2e6faef9e5309d9f", "url": "https://translate-dev.freebsd.org/api/units/615369/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:30.483744Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "Any codebase that will survive and be maintainable for years must therefore be designed properly from the beginning even if it costs some performance. Twenty years ago people were still arguing that programming in assembly was better than programming in a high-level language because it produced code that was ten times as fast. Today, the fallibility of that argument is obvious - as are the parallels to algorithmic design and code generalization." ], "previous_source": "", "target": [ "Any codebase that will survive and be maintainable for years must therefore be designed properly from the beginning even if it costs some performance. Twenty years ago people were still arguing that programming in assembly was better than programming in a high-level language because it produced code that was ten times as fast. Today, the fallibility of that argument is obvious - as are the parallels to algorithmic design and code generalization." ], "id_hash": -1172663613538271878, "content_hash": -1172663613538271878, "location": "documentation/content/en/articles/vm-design/_index.adoc:87", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 12, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 72, "source_unit": "https://translate-dev.freebsd.org/api/units/615371/?format=api", "priority": 100, "id": 615371, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=6fb9dca812067d7a", "url": "https://translate-dev.freebsd.org/api/units/615371/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:30.549050Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "The best way to begin describing the FreeBSD VM system is to look at it from the perspective of a user-level process. Each user process sees a single, private, contiguous VM address space containing several types of memory objects. These objects have various characteristics. Program code and program data are effectively a single memory-mapped file (the binary file being run), but program code is read-only while program data is copy-on-write. Program BSS is just memory allocated and filled with zeros on demand, called demand zero page fill. Arbitrary files can be memory-mapped into the address space as well, which is how the shared library mechanism works. Such mappings can require modifications to remain private to the process making them. The fork system call adds an entirely new dimension to the VM management problem on top of the complexity already given." ], "previous_source": "", "target": [ "The best way to begin describing the FreeBSD VM system is to look at it from the perspective of a user-level process. Each user process sees a single, private, contiguous VM address space containing several types of memory objects. These objects have various characteristics. Program code and program data are effectively a single memory-mapped file (the binary file being run), but program code is read-only while program data is copy-on-write. Program BSS is just memory allocated and filled with zeros on demand, called demand zero page fill. Arbitrary files can be memory-mapped into the address space as well, which is how the shared library mechanism works. Such mappings can require modifications to remain private to the process making them. The fork system call adds an entirely new dimension to the VM management problem on top of the complexity already given." ], "id_hash": 8563897145619441028, "content_hash": 8563897145619441028, "location": "documentation/content/en/articles/vm-design/_index.adoc:99", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 14, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 140, "source_unit": "https://translate-dev.freebsd.org/api/units/615373/?format=api", "priority": 100, "id": 615373, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=f6d9131499a0e584", "url": "https://translate-dev.freebsd.org/api/units/615373/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:30.819970Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "A program binary data page (which is a basic copy-on-write page) illustrates the complexity. A program binary contains a preinitialized data section which is initially mapped directly from the program file. When a program is loaded into a process's VM space, this area is initially memory-mapped and backed by the program binary itself, allowing the VM system to free/reuse the page and later load it back in from the binary. The moment a process modifies this data, however, the VM system must make a private copy of the page for that process. Since the private copy has been modified, the VM system may no longer free it, because there is no longer any way to restore it later on." ], "previous_source": "", "target": [ "A program binary data page (which is a basic copy-on-write page) illustrates the complexity. A program binary contains a preinitialized data section which is initially mapped directly from the program file. When a program is loaded into a process's VM space, this area is initially memory-mapped and backed by the program binary itself, allowing the VM system to free/reuse the page and later load it back in from the binary. The moment a process modifies this data, however, the VM system must make a private copy of the page for that process. Since the private copy has been modified, the VM system may no longer free it, because there is no longer any way to restore it later on." ], "id_hash": -1044570962678253903, "content_hash": -1044570962678253903, "location": "documentation/content/en/articles/vm-design/_index.adoc:105", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 15, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 119, "source_unit": "https://translate-dev.freebsd.org/api/units/615375/?format=api", "priority": 100, "id": 615375, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=7180f03e6adff6b1", "url": "https://translate-dev.freebsd.org/api/units/615375/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:31.050259Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "FreeBSD manages all of this with a layered VM Object model. The original binary program file winds up being the lowest VM Object layer. A copy-on-write layer is pushed on top of that to hold those pages which had to be copied from the original file. If the program modifies a data page belonging to the original file the VM system takes a fault and makes a copy of the page in the higher layer. When a process forks, additional VM Object layers are pushed on. This might make a little more sense with a fairly basic example. A `fork()` is a common operation for any *BSD system, so this example will consider a program that starts up, and forks. When the process starts, the VM system creates an object layer, let's call this A:" ], "previous_source": "", "target": [ "FreeBSD manages all of this with a layered VM Object model. The original binary program file winds up being the lowest VM Object layer. A copy-on-write layer is pushed on top of that to hold those pages which had to be copied from the original file. If the program modifies a data page belonging to the original file the VM system takes a fault and makes a copy of the page in the higher layer. When a process forks, additional VM Object layers are pushed on. This might make a little more sense with a fairly basic example. A `fork()` is a common operation for any *BSD system, so this example will consider a program that starts up, and forks. When the process starts, the VM system creates an object layer, let's call this A:" ], "id_hash": 3508589053702886792, "content_hash": 3508589053702886792, "location": "documentation/content/en/articles/vm-design/_index.adoc:121", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 17, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 135, "source_unit": "https://translate-dev.freebsd.org/api/units/615379/?format=api", "priority": 100, "id": 615379, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=b0b10327b0c8d588", "url": "https://translate-dev.freebsd.org/api/units/615379/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:31.909813Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "A represents the file-pages may be paged in and out of the file's physical media as necessary. Paging in from the disk is reasonable for a program, but we really do not want to page back out and overwrite the executable. The VM system therefore creates a second layer, B, that will be physically backed by swap space:" ], "previous_source": "", "target": [ "A represents the file-pages may be paged in and out of the file's physical media as necessary. Paging in from the disk is reasonable for a program, but we really do not want to page back out and overwrite the executable. The VM system therefore creates a second layer, B, that will be physically backed by swap space:" ], "id_hash": 669767678025411190, "content_hash": 669767678025411190, "location": "documentation/content/en/articles/vm-design/_index.adoc:127", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 20, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 58, "source_unit": "https://translate-dev.freebsd.org/api/units/615381/?format=api", "priority": 100, "id": 615381, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=894b7e2792be2a76", "url": "https://translate-dev.freebsd.org/api/units/615381/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:32.274777Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "On the first write to a page after this, a new page is created in B, and its contents are initialized from A. All pages in B can be paged in or out to a swap device. When the program forks, the VM system creates two new object layers-C1 for the parent, and C2 for the child-that rest on top of B:" ], "previous_source": "", "target": [ "On the first write to a page after this, a new page is created in B, and its contents are initialized from A. All pages in B can be paged in or out to a swap device. When the program forks, the VM system creates two new object layers-C1 for the parent, and C2 for the child-that rest on top of B:" ], "id_hash": -7044824120912214871, "content_hash": -7044824120912214871, "location": "documentation/content/en/articles/vm-design/_index.adoc:133", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 22, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 62, "source_unit": "https://translate-dev.freebsd.org/api/units/615383/?format=api", "priority": 100, "id": 615383, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=1e3bc1c97fec84a9", "url": "https://translate-dev.freebsd.org/api/units/615383/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:32.557739Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "In this case, let's say a page in B is modified by the original parent process. The process will take a copy-on-write fault and duplicate the page in C1, leaving the original page in B untouched. Now, let's say the same page in B is modified by the child process. The process will take a copy-on-write fault and duplicate the page in C2. The original page in B is now completely hidden since both C1 and C2 have a copy and B could theoretically be destroyed if it does not represent a \"real\" file; however, this sort of optimization is not trivial to make because it is so fine-grained. FreeBSD does not make this optimization. Now, suppose (as is often the case) that the child process does an `exec()`. Its current address space is usually replaced by a new address space representing a new file. In this case, the C2 layer is destroyed:" ], "previous_source": "", "target": [ "In this case, let's say a page in B is modified by the original parent process. The process will take a copy-on-write fault and duplicate the page in C1, leaving the original page in B untouched. Now, let's say the same page in B is modified by the child process. The process will take a copy-on-write fault and duplicate the page in C2. The original page in B is now completely hidden since both C1 and C2 have a copy and B could theoretically be destroyed if it does not represent a \"real\" file; however, this sort of optimization is not trivial to make because it is so fine-grained. FreeBSD does not make this optimization. Now, suppose (as is often the case) that the child process does an `exec()`. Its current address space is usually replaced by a new address space representing a new file. In this case, the C2 layer is destroyed:" ], "id_hash": -9136506890461498359, "content_hash": -9136506890461498359, "location": "documentation/content/en/articles/vm-design/_index.adoc:145", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 24, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 153, "source_unit": "https://translate-dev.freebsd.org/api/units/615385/?format=api", "priority": 100, "id": 615385, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=01349b63f2223409", "url": "https://translate-dev.freebsd.org/api/units/615385/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:32.761224Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "In this case, the number of children of B drops to one, and all accesses to B now go through C1. This means that B and C1 can be collapsed together. Any pages in B that also exist in C1 are deleted from B during the collapse. Thus, even though the optimization in the previous step could not be made, we can recover the dead pages when either of the processes exit or `exec()`." ], "previous_source": "", "target": [ "In this case, the number of children of B drops to one, and all accesses to B now go through C1. This means that B and C1 can be collapsed together. Any pages in B that also exist in C1 are deleted from B during the collapse. Thus, even though the optimization in the previous step could not be made, we can recover the dead pages when either of the processes exit or `exec()`." ], "id_hash": -3676186659215458374, "content_hash": -3676186659215458374, "location": "documentation/content/en/articles/vm-design/_index.adoc:152", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 26, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 74, "source_unit": "https://translate-dev.freebsd.org/api/units/615387/?format=api", "priority": 100, "id": 615387, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=4cfb8fb5f16ebfba", "url": "https://translate-dev.freebsd.org/api/units/615387/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:32.874369Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "This model creates a number of potential problems. The first is that you can wind up with a relatively deep stack of layered VM Objects which can cost scanning time and memory when you take a fault. Deep layering can occur when processes fork and then fork again (either parent or child). The second problem is that you can wind up with dead, inaccessible pages deep in the stack of VM Objects. In our last example if both the parent and child processes modify the same page, they both get their own private copies of the page and the original page in B is no longer accessible by anyone. That page in B can be freed." ], "previous_source": "", "target": [ "This model creates a number of potential problems. The first is that you can wind up with a relatively deep stack of layered VM Objects which can cost scanning time and memory when you take a fault. Deep layering can occur when processes fork and then fork again (either parent or child). The second problem is that you can wind up with dead, inaccessible pages deep in the stack of VM Objects. In our last example if both the parent and child processes modify the same page, they both get their own private copies of the page and the original page in B is no longer accessible by anyone. That page in B can be freed." ], "id_hash": -3201579251021163267, "content_hash": -3201579251021163267, "location": "documentation/content/en/articles/vm-design/_index.adoc:159", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 27, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 116, "source_unit": "https://translate-dev.freebsd.org/api/units/615389/?format=api", "priority": 100, "id": 615389, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=5391b4a2469f54fd", "url": "https://translate-dev.freebsd.org/api/units/615389/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:33.068855Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "FreeBSD solves the deep layering problem with a special optimization called the \"All Shadowed Case\". This case occurs if either C1 or C2 take sufficient COW faults to completely shadow all pages in B. Lets say that C1 achieves this. C1 can now bypass B entirely, so rather then have C1->B->A and C2->B->A we now have C1->A and C2->B->A. But look what also happened-now B has only one reference (C2), so we can collapse B and C2 together. The end result is that B is deleted entirely and we have C1->A and C2->A. It is often the case that B will contain a large number of pages and neither C1 nor C2 will be able to completely overshadow it. If we fork again and create a set of D layers, however, it is much more likely that one of the D layers will eventually be able to completely overshadow the much smaller dataset represented by C1 or C2. The same optimization will work at any point in the graph and the grand result of this is that even on a heavily forked machine VM Object stacks tend to not get much deeper then 4. This is true of both the parent and the children and true whether the parent is doing the forking or whether the children cascade forks." ], "previous_source": "", "target": [ "FreeBSD solves the deep layering problem with a special optimization called the \"All Shadowed Case\". This case occurs if either C1 or C2 take sufficient COW faults to completely shadow all pages in B. Lets say that C1 achieves this. C1 can now bypass B entirely, so rather then have C1->B->A and C2->B->A we now have C1->A and C2->B->A. But look what also happened-now B has only one reference (C2), so we can collapse B and C2 together. The end result is that B is deleted entirely and we have C1->A and C2->A. It is often the case that B will contain a large number of pages and neither C1 nor C2 will be able to completely overshadow it. If we fork again and create a set of D layers, however, it is much more likely that one of the D layers will eventually be able to completely overshadow the much smaller dataset represented by C1 or C2. The same optimization will work at any point in the graph and the grand result of this is that even on a heavily forked machine VM Object stacks tend to not get much deeper then 4. This is true of both the parent and the children and true whether the parent is doing the forking or whether the children cascade forks." ], "id_hash": 8401165672617129096, "content_hash": 8401165672617129096, "location": "documentation/content/en/articles/vm-design/_index.adoc:170", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 28, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 219, "source_unit": "https://translate-dev.freebsd.org/api/units/615391/?format=api", "priority": 100, "id": 615391, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=f496efaaff8cb488", "url": "https://translate-dev.freebsd.org/api/units/615391/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:33.549911Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "The dead page problem still exists in the case where C1 or C2 do not completely overshadow B. Due to our other optimizations this case does not represent much of a problem and we simply allow the pages to be dead. If the system runs low on memory it will swap them out, eating a little swap, but that is it." ], "previous_source": "", "target": [ "The dead page problem still exists in the case where C1 or C2 do not completely overshadow B. Due to our other optimizations this case does not represent much of a problem and we simply allow the pages to be dead. If the system runs low on memory it will swap them out, eating a little swap, but that is it." ], "id_hash": 5007560720226111764, "content_hash": 5007560720226111764, "location": "documentation/content/en/articles/vm-design/_index.adoc:174", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 29, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 61, "source_unit": "https://translate-dev.freebsd.org/api/units/615393/?format=api", "priority": 100, "id": 615393, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=c57e6df1a046d114", "url": "https://translate-dev.freebsd.org/api/units/615393/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:33.912873Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "The advantage to the VM Object model is that `fork()` is extremely fast, since no real data copying need take place. The disadvantage is that you can build a relatively complex VM Object layering that slows page fault handling down a little, and you spend memory managing the VM Object structures. The optimizations FreeBSD makes proves to reduce the problems enough that they can be ignored, leaving no real disadvantage." ], "previous_source": "", "target": [ "The advantage to the VM Object model is that `fork()` is extremely fast, since no real data copying need take place. The disadvantage is that you can build a relatively complex VM Object layering that slows page fault handling down a little, and you spend memory managing the VM Object structures. The optimizations FreeBSD makes proves to reduce the problems enough that they can be ignored, leaving no real disadvantage." ], "id_hash": -5357844410067895347, "content_hash": -5357844410067895347, "location": "documentation/content/en/articles/vm-design/_index.adoc:178", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 30, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 70, "source_unit": "https://translate-dev.freebsd.org/api/units/615395/?format=api", "priority": 100, "id": 615395, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=35a51ce568173bcd", "url": "https://translate-dev.freebsd.org/api/units/615395/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:34.042162Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/en/?format=api", "source": [ "Private data pages are initially either copy-on-write or zero-fill pages. When a change, and therefore a copy, is made, the original backing object (usually a file) can no longer be used to save a copy of the page when the VM system needs to reuse it for other purposes. This is where SWAP comes in. SWAP is allocated to create backing store for memory that does not otherwise have it. FreeBSD allocates the swap management structure for a VM Object only when it is actually needed. However, the swap management structure has had problems historically:" ], "previous_source": "", "target": [ "Private data pages are initially either copy-on-write or zero-fill pages. When a change, and therefore a copy, is made, the original backing object (usually a file) can no longer be used to save a copy of the page when the VM system needs to reuse it for other purposes. This is where SWAP comes in. SWAP is allocated to create backing store for memory that does not otherwise have it. FreeBSD allocates the swap management structure for a VM Object only when it is actually needed. However, the swap management structure has had problems historically:" ], "id_hash": 1315532285212979335, "content_hash": 1315532285212979335, "location": "documentation/content/en/articles/vm-design/_index.adoc:188", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 100, "fuzzy": false, "translated": true, "approved": false, "position": 32, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 95, "source_unit": "https://translate-dev.freebsd.org/api/units/615397/?format=api", "priority": 100, "id": 615397, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/en/?checksum=9241b5a4b6ad7087", "url": "https://translate-dev.freebsd.org/api/units/615397/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2021-03-20T20:43:34.464414Z" } ] }