Lines Matching +full:many +full:- +full:to +full:- +full:one
18 But in the future it can expand to other filesystems.
28 requiring larger clear-page copy-page in page faults which is a
34 factor will affect all subsequent accesses to the memory for the whole
46 hugepages but a significant speedup already happens if only one of
48 going to run faster.
50 THP can be enabled system wide or restricted to certain tasks or even
59 if compared to the reservation approach of hugetlbfs by allowing all
60 unused memory to be used as cache or other movable (or even unmovable
61 entities). It doesn't require reservation to prevent hugepage
62 allocation failures to be noticeable from userland. It allows paging
63 and all other advanced VM features to be available on the
64 hugepages. It requires no modifications for applications to take
67 Applications however can be further optimized to take advantage of
68 this feature, like for example they've been optimized before to avoid
78 possible to disable hugepages system-wide and to only have them inside
82 to eliminate any risk of wasting any precious byte of memory and to
86 risk to lose memory by using hugepages, should use
95 -------------------
99 regions (to avoid the risk of consuming more memory resources) or enabled
100 system wide. This can be achieved with one of::
106 It's also possible to limit defrag efforts in the VM to generate
107 anonymous hugepages in case they're not immediately free to madvise
108 regions or to never try to defrag memory and simply fallback to regular
110 time to defrag memory, we would expect to gain even more by the fact we
126 memory in an effort to allocate a THP immediately. This may be
128 use and are willing to delay the VM start to utilise them.
132 to reclaim pages and wake kcompactd to compact memory so that
134 of khugepaged to then install the THP pages later.
139 other regions will wake kswapd in the background to reclaim
140 pages and wake kcompactd to compact memory so that THP is
149 should be self-explanatory.
151 By default kernel tries to use huge zero page on read page fault to
152 anonymous mapping. It's possible to disable huge zero page by writing 0
159 library) may want to know the size (in bytes) of a transparent hugepage::
164 transparent_hugepage/enabled is set to "always" or "madvise, and it'll
165 be automatically shutdown if it's set to "never".
168 -------------------
170 khugepaged runs usually at low frequency so while one may not want to
173 also possible to disable defrag in khugepaged by writing 0 or enable
179 You can also control how many pages khugepaged should scan at each
184 and how many milliseconds to wait in khugepaged between each pass (you
185 can set this to 0 to run khugepaged at 100% utilization of one core)::
189 and how many milliseconds to wait in khugepaged if there's an hugepage
190 allocation failure to throttle the next allocation attempt::
202 ``max_ptes_none`` specifies how many extra small pages (that are
204 of small pages into one large page::
208 A higher value leads to use additional memory for programs.
209 A lower value leads to gain less thp performance. Value of
213 ``max_ptes_swap`` specifies how many pages can be brought in from
223 ``max_ptes_shared`` specifies how many pages can be shared across multiple
236 to the kernel command line.
245 Attempt to allocate huge pages every time we need a new page;
259 ``mount -o remount,huge= /mountpoint`` works fine after mount: remounting
260 ``huge=never`` will not attempt to break up huge pages at all, just stop more
263 There's also sysfs knob to control hugepage allocation policy for internal
268 In addition to policies listed above, shmem_enabled allows two further
272 For use in emergencies, to force the huge option off from
275 Force the huge option on for all - very useful for testing;
281 future behavior. So to make them effective you need to restart any
282 application that could have been using hugepages. This also applies to the
290 To identify what applications are using anonymous transparent huge pages,
291 it is necessary to read ``/proc/PID/smaps`` and count the AnonHugePages fields
294 The number of file transparent huge pages mapped to userspace is available
296 To identify what applications are mapping file transparent huge pages, it
297 is necessary to read ``/proc/PID/smaps`` and count the FileHugeMapped fields
303 There are a number of counters in ``/proc/vmstat`` that may be used to
308 allocated to handle a page fault.
312 a range of pages to collapse into one huge page and has
313 successfully allocated a new huge page to store the data.
316 is incremented if a page fault fails to allocate
317 a huge page and instead falls back to using small pages.
320 is incremented if a page fault fails to charge a huge page and
321 instead falls back to using small pages even though the
326 of pages that should be collapsed into one huge page but failed
334 is incremented if a file huge page is attempted to be allocated
335 but fails and instead falls back to using small pages.
339 falls back to using small pages even though the allocation was
353 is incremented if kernel fails to split huge
360 going to be split under memory pressure.
375 is incremented if kernel fails to allocate
376 huge zero page and falls back to using small pages.
379 is incremented every time a huge page is swapout in one
383 is incremented if a huge page has to be split before swapout.
384 Usually because failed to allocate some continuous swap space
388 system uses memory compaction to copy data around memory to free a
389 huge page for use. There are some counters in ``/proc/vmstat`` to help
393 is incremented every time a process stalls to run
401 is incremented if the system tries to compact memory
407 is copying a lot of data to satisfy the huge page allocation.
419 It is possible to establish how long the stalls were using the function
420 tracer to record how long was spent in __alloc_pages_nodemask and
421 using the mm_page_alloc tracepoint to identify which allocations were
427 To be guaranteed that the kernel will map a 2M page immediately in any
428 memory region, the mmap region has to be hugepage naturally
437 usual features belonging to hugetlbfs are preserved and