admin-guide/mm/transhuge.rst

13 using huge pages for the backing of virtual memory with huge pages
22    the huge page size is 2M, although the actual numbers may vary
53 collapses sequences of basic pages into huge pages.
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
214 swap when collapsing a group of pages into a transparent huge page::
242 ``huge=``. It can have following values:
245     Attempt to allocate huge pages every time we need a new page;
248     Do not allocate huge pages;
251     Only allocate huge page if it will be fully within i_size.
255     Only allocate huge pages if requested with fadvise()/madvise();
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
272     For use in emergencies, to force the huge option off from
275     Force the huge option on for all - very useful for testing;
288 The number of anonymous transparent huge pages currently used by the
290 To identify what applications are using anonymous transparent huge pages,
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
304 monitor how successfully the system is providing huge pages for use.
307 	is incremented every time a huge page is successfully
312 	a range of pages to collapse into one huge page and has
313 	successfully allocated a new huge page to store the data.
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
326 	of pages that should be collapsed into one huge page but failed
330 	is incremented every time a file huge page is successfully
334 	is incremented if a file huge page is attempted to be allocated
338 	is incremented if a file huge page cannot be charged and instead
343 	is incremented every time a file huge page is mapped into
347 	is incremented every time a huge page is split into base
349 	reason is that a huge page is old and is being reclaimed.
353 	is incremented if kernel fails to split huge
357 	is incremented when a huge page is put onto split
358 	queue. This happens when a huge page is partially unmapped and
365 	munmap() on part of huge page. It doesn't split huge page, only
369 	is incremented every time a huge zero page is
372 	every map of the huge zero page, only its allocation.
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.
385 	for the huge page.
387 As the system ages, allocating huge pages may be expensive as the
389 huge page for use. There are some counters in ``/proc/vmstat`` to help
394 	memory compaction so that a huge page is free for use.
398 	freed a huge page for use.
407 	is copying a lot of data to satisfy the huge page allocation.
417 	a huge page aligned range of pages.
422 for huge pages.