Units
Translation components API.
See the Weblate's Web API documentation for detailed description of the API.
GET /api/translations/documentation/articlesvm-design_index/el/units/?format=api&page=2
{ "count": 82, "next": null, "previous": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/units/?format=api", "results": [ { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "FreeBSD makes use of several page queues to further refine the selection of pages to reuse as well as to determine when dirty pages must be flushed to their backing store. Since page tables are dynamic entities under FreeBSD, it costs virtually nothing to unmap a page from the address space of any processes using it. When a page candidate has been chosen based on the page-use counter, this is precisely what is done. The system must make a distinction between clean pages which can theoretically be freed up at any time, and dirty pages which must first be written to their backing store before being reusable. When a page candidate has been found it is moved to the inactive queue if it is dirty, or the cache queue if it is clean. A separate algorithm based on the dirty-to-clean page ratio determines when dirty pages in the inactive queue must be flushed to disk. Once this is accomplished, the flushed pages are moved from the inactive queue to the cache queue. At this point, pages in the cache queue can still be reactivated by a VM fault at relatively low cost. However, pages in the cache queue are considered to be \"immediately freeable\" and will be reused in an LRU (least-recently used) fashion when the system needs to allocate new memory." ], "previous_source": "", "target": [ "" ], "id_hash": 2673623526903959567, "content_hash": 2673623526903959567, "location": "documentation/content/en/articles/vm-design/_index.adoc:245", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 52, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 222, "source_unit": "https://translate-dev.freebsd.org/api/units/615411/?format=api", "priority": 100, "id": 1653619, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=a51a9e6ea83cd00f", "url": "https://translate-dev.freebsd.org/api/units/1653619/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.622304Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "It is important to note that the FreeBSD VM system attempts to separate clean and dirty pages for the express reason of avoiding unnecessary flushes of dirty pages (which eats I/O bandwidth), nor does it move pages between the various page queues gratuitously when the memory subsystem is not being stressed. This is why you will see some systems with very low cache queue counts and high active queue counts when doing a `systat -vm` command. As the VM system becomes more stressed, it makes a greater effort to maintain the various page queues at the levels determined to be the most effective." ], "previous_source": "", "target": [ "" ], "id_hash": 7639403564355480804, "content_hash": 7639403564355480804, "location": "documentation/content/en/articles/vm-design/_index.adoc:249", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 53, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 103, "source_unit": "https://translate-dev.freebsd.org/api/units/615413/?format=api", "priority": 100, "id": 1653620, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=ea049d110542ece4", "url": "https://translate-dev.freebsd.org/api/units/1653620/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.623088Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "An urban myth has circulated for years that Linux did a better job avoiding swapouts than FreeBSD, but this in fact is not true. What was actually occurring was that FreeBSD was proactively paging out unused pages to make room for more disk cache while Linux was keeping unused pages in core and leaving less memory available for cache and process pages. I do not know whether this is still true today." ], "previous_source": "", "target": [ "" ], "id_hash": 5780403638740543814, "content_hash": 5780403638740543814, "location": "documentation/content/en/articles/vm-design/_index.adoc:253", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 54, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 72, "source_unit": "https://translate-dev.freebsd.org/api/units/1569363/?format=api", "priority": 100, "id": 1653621, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=d0381e7bc9816946", "url": "https://translate-dev.freebsd.org/api/units/1653621/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.623797Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "Pre-Faulting and Zeroing Optimizations" ], "previous_source": "", "target": [ "" ], "id_hash": -7199560516843032198, "content_hash": -7199560516843032198, "location": "documentation/content/en/articles/vm-design/_index.adoc:255", "context": "", "note": "type: Title ==", "flags": "no-wrap", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 55, "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": 1653622, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=1c1605dad6a4b17a", "url": "https://translate-dev.freebsd.org/api/units/1653622/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.624458Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "Taking a VM fault is not expensive if the underlying page is already in core and can simply be mapped into the process, but it can become expensive if you take a whole lot of them on a regular basis. A good example of this is running a program such as man:ls[1] or man:ps[1] over and over again. If the program binary is mapped into memory but not mapped into the page table, then all the pages that will be accessed by the program will have to be faulted in every time the program is run. This is unnecessary when the pages in question are already in the VM Cache, so FreeBSD will attempt to pre-populate a process's page tables with those pages that are already in the VM Cache. One thing that FreeBSD does not yet do is pre-copy-on-write certain pages on exec. For example, if you run the man:ls[1] program while running `vmstat 1` you will notice that it always takes a certain number of page faults, even when you run it over and over again. These are zero-fill faults, not program code faults (which were pre-faulted in already). Pre-copying pages on exec or fork is an area that could use more study." ], "previous_source": "", "target": [ "" ], "id_hash": -8125128984177974447, "content_hash": -8125128984177974447, "location": "documentation/content/en/articles/vm-design/_index.adoc:265", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 56, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 205, "source_unit": "https://translate-dev.freebsd.org/api/units/615417/?format=api", "priority": 100, "id": 1653623, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=0f3dbe3cd7d76351", "url": "https://translate-dev.freebsd.org/api/units/1653623/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.625125Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "A large percentage of page faults that occur are zero-fill faults. You can usually see this by observing the `vmstat -s` output. These occur when a process accesses pages in its BSS area. The BSS area is expected to be initially zero but the VM system does not bother to allocate any memory at all until the process actually accesses it. When a fault occurs the VM system must not only allocate a new page, it must zero it as well. To optimize the zeroing operation the VM system has the ability to pre-zero pages and mark them as such, and to request pre-zeroed pages when zero-fill faults occur. The pre-zeroing occurs whenever the CPU is idle but the number of pages the system pre-zeros is limited to avoid blowing away the memory caches. This is an excellent example of adding complexity to the VM system to optimize the critical path." ], "previous_source": "", "target": [ "" ], "id_hash": -3287937168931606517, "content_hash": -3287937168931606517, "location": "documentation/content/en/articles/vm-design/_index.adoc:274", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 57, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 151, "source_unit": "https://translate-dev.freebsd.org/api/units/1569365/?format=api", "priority": 100, "id": 1653624, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=525ee690aa07300b", "url": "https://translate-dev.freebsd.org/api/units/1653624/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.625912Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "Page Table Optimizations" ], "previous_source": "", "target": [ "" ], "id_hash": 7381999408203105810, "content_hash": 7381999408203105810, "location": "documentation/content/en/articles/vm-design/_index.adoc:276", "context": "", "note": "type: Title ==", "flags": "no-wrap", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 58, "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": 1653625, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=e6722159aa170612", "url": "https://translate-dev.freebsd.org/api/units/1653625/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.626631Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "The page table optimizations make up the most contentious part of the FreeBSD VM design and they have shown some strain with the advent of serious use of `mmap()`. I think this is actually a feature of most BSDs though I am not sure when it was first introduced. There are two major optimizations. The first is that hardware page tables do not contain persistent state but instead can be thrown away at any time with only a minor amount of management overhead. The second is that every active page table entry in the system has a governing `pv_entry` structure which is tied into the `vm_page` structure. FreeBSD can simply iterate through those mappings that are known to exist while Linux must check all page tables that _might_ contain a specific mapping to see if it does, which can achieve O(n^2) overhead in certain situations. It is because of this that FreeBSD tends to make better choices on which pages to reuse or swap when memory is stressed, giving it better performance under load. However, FreeBSD requires kernel tuning to accommodate large-shared-address-space situations such as those that can occur in a news system because it may run out of `pv_entry` structures." ], "previous_source": "", "target": [ "" ], "id_hash": -6307955811766454775, "content_hash": -6307955811766454775, "location": "documentation/content/en/articles/vm-design/_index.adoc:286", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 59, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 201, "source_unit": "https://translate-dev.freebsd.org/api/units/615421/?format=api", "priority": 100, "id": 1653626, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=2875a39c34ccb609", "url": "https://translate-dev.freebsd.org/api/units/1653626/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.627250Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "Both Linux and FreeBSD need work in this area. FreeBSD is trying to maximize the advantage of a potentially sparse active-mapping model (not all processes need to map all pages of a shared library, for example), whereas Linux is trying to simplify its algorithms. FreeBSD generally has the performance advantage here at the cost of wasting a little extra memory, but FreeBSD breaks down in the case where a large file is massively shared across hundreds of processes. Linux, on the other hand, breaks down in the case where many processes are sparsely-mapping the same shared library and also runs non-optimally when trying to determine whether a page can be reused or not." ], "previous_source": "", "target": [ "" ], "id_hash": 60250029008486510, "content_hash": 60250029008486510, "location": "documentation/content/en/articles/vm-design/_index.adoc:291", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 60, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 113, "source_unit": "https://translate-dev.freebsd.org/api/units/615423/?format=api", "priority": 100, "id": 1653627, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=80d60d1508c2006e", "url": "https://translate-dev.freebsd.org/api/units/1653627/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.628049Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "Conclusion" ], "previous_source": "", "target": [ "" ], "id_hash": -438954553492005104, "content_hash": -438954553492005104, "location": "documentation/content/en/articles/vm-design/_index.adoc:293", "context": "", "note": "type: Title ==", "flags": "no-wrap", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 61, "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": 1653631, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=79e88528c6919f10", "url": "https://translate-dev.freebsd.org/api/units/1653631/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.630886Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "Virtual memory in modern operating systems must address a number of different issues efficiently and for many different usage patterns. The modular and algorithmic approach that BSD has historically taken allows us to study and understand the current implementation as well as relatively cleanly replace large sections of the code. There have been a number of improvements to the FreeBSD VM system in the last several years, and work is ongoing." ], "previous_source": "", "target": [ "" ], "id_hash": -2528742712089608106, "content_hash": -2528742712089608106, "location": "documentation/content/en/articles/vm-design/_index.adoc:298", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 62, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 71, "source_unit": "https://translate-dev.freebsd.org/api/units/615429/?format=api", "priority": 100, "id": 1653632, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=5ce819e6b58a8056", "url": "https://translate-dev.freebsd.org/api/units/1653632/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.631483Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "Bonus QA session by Allen Briggs" ], "previous_source": "", "target": [ "" ], "id_hash": -3193954519288190759, "content_hash": -3193954519288190759, "location": "documentation/content/en/articles/vm-design/_index.adoc:300", "context": "", "note": "type: Title ==", "flags": "no-wrap", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 63, "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": 1653633, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=53accb497912e8d9", "url": "https://translate-dev.freebsd.org/api/units/1653633/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.632171Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?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": [ "" ], "id_hash": -648622040058245068, "content_hash": -648622040058245068, "location": "documentation/content/en/articles/vm-design/_index.adoc:302", "context": "", "note": "type: Title ===", "flags": "no-wrap", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 64, "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": 1653634, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=76ffa1b0ecd6d034", "url": "https://translate-dev.freebsd.org/api/units/1653634/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.632789Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "FreeBSD uses a fixed swap interleave which defaults to 4. This means that FreeBSD reserves space for four swap areas even if you only have one, two, or three. Since swap is interleaved the linear address space representing the \"four swap areas\" will be fragmented if you do not actually have four swap areas. For example, if you have two swap areas A and B FreeBSD's address space representation for that swap area will be interleaved in blocks of 16 pages:" ], "previous_source": "", "target": [ "" ], "id_hash": 2352136694481216650, "content_hash": 2352136694481216650, "location": "documentation/content/en/articles/vm-design/_index.adoc:308", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 65, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 81, "source_unit": "https://translate-dev.freebsd.org/api/units/615431/?format=api", "priority": 100, "id": 1653635, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=a0a477dc89b6e48a", "url": "https://translate-dev.freebsd.org/api/units/1653635/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.633426Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "A B C D A B C D A B C D A B C D\n" ], "previous_source": "", "target": [ "" ], "id_hash": 922062017217951916, "content_hash": 922062017217951916, "location": "documentation/content/en/articles/vm-design/_index.adoc:311", "context": "", "note": "type: delimited block . 4", "flags": "no-wrap", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 66, "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": 1653636, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=8ccbd284f527f8ac", "url": "https://translate-dev.freebsd.org/api/units/1653636/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.634103Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "FreeBSD 3.X uses a \"sequential list of free regions\" approach to accounting for the free swap areas. The idea is that large blocks of free linear space can be represented with a single list node ([.filename]#kern/subr_rlist.c#). But due to the fragmentation the sequential list winds up being insanely fragmented. In the above example, completely unused swap will have A and B shown as \"free\" and C and D shown as \"all allocated\". Each A-B sequence requires a list node to account for because C and D are holes, so the list node cannot be combined with the next A-B sequence." ], "previous_source": "", "target": [ "" ], "id_hash": 5525637408233093798, "content_hash": 5525637408233093798, "location": "documentation/content/en/articles/vm-design/_index.adoc:318", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 67, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 100, "source_unit": "https://translate-dev.freebsd.org/api/units/615433/?format=api", "priority": 100, "id": 1653637, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=ccaf01f25b57faa6", "url": "https://translate-dev.freebsd.org/api/units/1653637/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.634749Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?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": [ "" ], "id_hash": -5189863536442483307, "content_hash": -5189863536442483307, "location": "documentation/content/en/articles/vm-design/_index.adoc:320", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 68, "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": 1653638, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=37f9e69c5597dd95", "url": "https://translate-dev.freebsd.org/api/units/1653638/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.635428Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "The fragmentation causes other problems. Being a linear list under 3.X, and having such a huge amount of inherent fragmentation, allocating and freeing swap winds up being an O(N) algorithm instead of an O(1) algorithm. Combined with other factors (heavy swapping) and you start getting into O(N^2) and O(N^3) levels of overhead, which is bad. The 3.X system may also need to allocate KVM during a swap operation to create a new list node which can lead to a deadlock if the system is trying to pageout pages in a low-memory situation." ], "previous_source": "", "target": [ "" ], "id_hash": -7933960118181456140, "content_hash": -7933960118181456140, "location": "documentation/content/en/articles/vm-design/_index.adoc:325", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 69, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 92, "source_unit": "https://translate-dev.freebsd.org/api/units/615435/?format=api", "priority": 100, "id": 1653639, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=11e4e94ef5ad96f4", "url": "https://translate-dev.freebsd.org/api/units/1653639/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.636083Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "Under 4.X we do not use a sequential list. Instead we use a radix tree and bitmaps of swap blocks rather than ranged list nodes. We take the hit of preallocating all the bitmaps required for the entire swap area up front but it winds up wasting less memory due to the use of a bitmap (one bit per block) instead of a linked list of nodes. The use of a radix tree instead of a sequential list gives us nearly O(1) performance no matter how fragmented the tree becomes." ], "previous_source": "", "target": [ "" ], "id_hash": 4155145828883344859, "content_hash": 4155145828883344859, "location": "documentation/content/en/articles/vm-design/_index.adoc:330", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 70, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 90, "source_unit": "https://translate-dev.freebsd.org/api/units/615437/?format=api", "priority": 100, "id": 1653640, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=b9aa0b1dd089addb", "url": "https://translate-dev.freebsd.org/api/units/1653640/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.636810Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?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": [ "" ], "id_hash": 3353279667003563824, "content_hash": 3353279667003563824, "location": "documentation/content/en/articles/vm-design/_index.adoc:331", "context": "", "note": "type: Title ===", "flags": "no-wrap", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 71, "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": 1653641, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=ae893e1738499f30", "url": "https://translate-dev.freebsd.org/api/units/1653641/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.637476Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "Yes, that is confusing. The relationship is \"goal\" verses \"reality\". Our goal is to separate the pages but the reality is that if we are not in a memory crunch, we do not really have to." ], "previous_source": "", "target": [ "" ], "id_hash": -460051008278140723, "content_hash": -460051008278140723, "location": "documentation/content/en/articles/vm-design/_index.adoc:336", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 72, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 36, "source_unit": "https://translate-dev.freebsd.org/api/units/615439/?format=api", "priority": 100, "id": 1653642, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=799d920ba10568cd", "url": "https://translate-dev.freebsd.org/api/units/1653642/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.638124Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?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": [ "" ], "id_hash": -5926730276734892911, "content_hash": -5926730276734892911, "location": "documentation/content/en/articles/vm-design/_index.adoc:338", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 73, "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": 1653643, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=2dc00636e7aa0491", "url": "https://translate-dev.freebsd.org/api/units/1653643/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.638770Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?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": [ "" ], "id_hash": 7433035198401274017, "content_hash": 7433035198401274017, "location": "documentation/content/en/articles/vm-design/_index.adoc:339", "context": "", "note": "type: Title ===", "flags": "no-wrap", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 74, "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": 1653644, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=e72772218baee0a1", "url": "https://translate-dev.freebsd.org/api/units/1653644/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.639410Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "A COW fault can be either zero-fill or program-data. The mechanism is the same either way because the backing program-data is almost certainly already in the cache. I am indeed lumping the two together. FreeBSD does not pre-COW program data or zero-fill, but it _does_ pre-map pages that exist in its cache." ], "previous_source": "", "target": [ "" ], "id_hash": 4210968952427581281, "content_hash": 4210968952427581281, "location": "documentation/content/en/articles/vm-design/_index.adoc:345", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 75, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 52, "source_unit": "https://translate-dev.freebsd.org/api/units/615441/?format=api", "priority": 100, "id": 1653645, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=ba705df399a50f61", "url": "https://translate-dev.freebsd.org/api/units/1653645/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.640043Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?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": [ "" ], "id_hash": -131807252796287441, "content_hash": -131807252796287441, "location": "documentation/content/en/articles/vm-design/_index.adoc:346", "context": "", "note": "type: Title ===", "flags": "no-wrap", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 76, "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": 1653646, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=7e2bba007e41d62f", "url": "https://translate-dev.freebsd.org/api/units/1653646/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.640694Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "A `vm_page` represents an (object,index#) tuple. A `pv_entry` represents a hardware page table entry (pte). If you have five processes sharing the same physical page, and three of those processes's page tables actually map the page, that page will be represented by a single `vm_page` structure and three `pv_entry` structures." ], "previous_source": "", "target": [ "" ], "id_hash": -6972689839131770923, "content_hash": -6972689839131770923, "location": "documentation/content/en/articles/vm-design/_index.adoc:350", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 77, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 50, "source_unit": "https://translate-dev.freebsd.org/api/units/615443/?format=api", "priority": 100, "id": 1653647, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=1f3c0788c1933fd5", "url": "https://translate-dev.freebsd.org/api/units/1653647/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.641359Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "`pv_entry` structures only represent pages mapped by the MMU (one `pv_entry` represents one pte). This means that when we need to remove all hardware references to a `vm_page` (to reuse the page for something else, page it out, clear it, dirty it, and so forth) we can simply scan the linked list of pv_entry's associated with that vm_page to remove or modify the pte's from their page tables." ], "previous_source": "", "target": [ "" ], "id_hash": 2530387555015900761, "content_hash": 2530387555015900761, "location": "documentation/content/en/articles/vm-design/_index.adoc:353", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 78, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 68, "source_unit": "https://translate-dev.freebsd.org/api/units/1569367/?format=api", "priority": 100, "id": 1653648, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=a31dbe1320cabe59", "url": "https://translate-dev.freebsd.org/api/units/1653648/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.641990Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "Under Linux there is no such linked list. To remove all the hardware page table mappings for a `vm_page` linux must index into every VM object that _might_ have mapped the page. For example, if you have 50 processes all mapping the same shared library and want to get rid of page X in that library, you need to index into the page table for each of those 50 processes even if only 10 of them have actually mapped the page. So Linux is trading off the simplicity of its design against performance. Many VM algorithms which are O(1) or (small N) under FreeBSD wind up being O(N), O(N^2), or worse under Linux. Since the pte's representing a particular page in an object tend to be at the same offset in all the page tables they are mapped in, reducing the number of accesses into the page tables at the same pte offset will often avoid blowing away the L1 cache line for that offset, which can lead to better performance." ], "previous_source": "", "target": [ "" ], "id_hash": -6410095001383200919, "content_hash": -6410095001383200919, "location": "documentation/content/en/articles/vm-design/_index.adoc:360", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 79, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 171, "source_unit": "https://translate-dev.freebsd.org/api/units/1569369/?format=api", "priority": 100, "id": 1653649, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=270ac48ef20c1769", "url": "https://translate-dev.freebsd.org/api/units/1653649/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.642651Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "FreeBSD has added complexity (the `pv_entry` scheme) to increase performance (to limit page table accesses to _only_ those pte's that need to be modified)." ], "previous_source": "", "target": [ "" ], "id_hash": 2794379834289832262, "content_hash": 2794379834289832262, "location": "documentation/content/en/articles/vm-design/_index.adoc:362", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 80, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 24, "source_unit": "https://translate-dev.freebsd.org/api/units/1569371/?format=api", "priority": 100, "id": 1653650, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=a6c7a1a76e5c4146", "url": "https://translate-dev.freebsd.org/api/units/1653650/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.643412Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "But FreeBSD has a scaling problem that Linux does not in that there are a limited number of `pv_entry` structures and this causes problems when you have massive sharing of data. In this case you may run out of `pv_entry` structures even though there is plenty of free memory available. This can be fixed easily enough by bumping up the number of `pv_entry` structures in the kernel config, but we really need to find a better way to do it." ], "previous_source": "", "target": [ "" ], "id_hash": 3727233459493505828, "content_hash": 3727233459493505828, "location": "documentation/content/en/articles/vm-design/_index.adoc:366", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 81, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 80, "source_unit": "https://translate-dev.freebsd.org/api/units/615449/?format=api", "priority": 100, "id": 1653651, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=b3b9cb156c0f8b24", "url": "https://translate-dev.freebsd.org/api/units/1653651/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.644045Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "In regards to the memory overhead of a page table verses the `pv_entry` scheme: Linux uses \"permanent\" page tables that are not throw away, but does not need a `pv_entry` for each potentially mapped pte. FreeBSD uses \"throw away\" page tables but adds in a `pv_entry` structure for each actually-mapped pte. I think memory utilization winds up being about the same, giving FreeBSD an algorithmic advantage with its ability to throw away page tables at will with very low overhead." ], "previous_source": "", "target": [ "" ], "id_hash": -1297362570668637025, "content_hash": -1297362570668637025, "location": "documentation/content/en/articles/vm-design/_index.adoc:369", "context": "", "note": "type: Plain text", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 82, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 80, "source_unit": "https://translate-dev.freebsd.org/api/units/615451/?format=api", "priority": 100, "id": 1653652, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=6dfed79d9e68849f", "url": "https://translate-dev.freebsd.org/api/units/1653652/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2024-02-17T12:53:25.644711Z" }, { "translation": "https://translate-dev.freebsd.org/api/translations/documentation/articlesvm-design_index/el/?format=api", "source": [ "This document is outdated and some sections do not accurately describe the current state of the VM system. It is retained for historical purposes and may be updated over time." ], "previous_source": "", "target": [ "" ], "id_hash": -2912390195825704450, "content_hash": -2912390195825704450, "location": "documentation/content/en/articles/vm-design/_index.adoc:46", "context": "", "note": "type: delimited block = 4", "flags": "", "labels": [], "state": 0, "fuzzy": false, "translated": false, "approved": false, "position": 3, "has_suggestion": false, "has_comment": false, "has_failing_check": false, "num_words": 30, "source_unit": "https://translate-dev.freebsd.org/api/units/1814001/?format=api", "priority": 100, "id": 1814003, "web_url": "https://translate-dev.freebsd.org/translate/documentation/articlesvm-design_index/el/?checksum=57951c8c227a81fe", "url": "https://translate-dev.freebsd.org/api/units/1814003/?format=api", "explanation": "", "extra_flags": "", "pending": false, "timestamp": "2025-06-29T20:54:09.600101Z" } ] }