diff options
Diffstat (limited to 'Documentation/vm')
| -rw-r--r-- | Documentation/vm/page_owner.txt | 9 | ||||
| -rw-r--r-- | Documentation/vm/slub.txt | 4 | ||||
| -rw-r--r-- | Documentation/vm/transhuge.txt | 22 |
3 files changed, 29 insertions, 6 deletions
diff --git a/Documentation/vm/page_owner.txt b/Documentation/vm/page_owner.txt index 8f3ce9b3aa11..ffff1439076a 100644 --- a/Documentation/vm/page_owner.txt +++ b/Documentation/vm/page_owner.txt @@ -28,10 +28,11 @@ with page owner and page owner is disabled in runtime due to no enabling boot option, runtime overhead is marginal. If disabled in runtime, it doesn't require memory to store owner information, so there is no runtime memory overhead. And, page owner inserts just two unlikely branches into -the page allocator hotpath and if it returns false then allocation is -done like as the kernel without page owner. These two unlikely branches -would not affect to allocation performance. Following is the kernel's -code size change due to this facility. +the page allocator hotpath and if not enabled, then allocation is done +like as the kernel without page owner. These two unlikely branches should +not affect to allocation performance, especially if the static keys jump +label patching functionality is available. Following is the kernel's code +size change due to this facility. - Without page owner text data bss dec hex filename diff --git a/Documentation/vm/slub.txt b/Documentation/vm/slub.txt index f0d340959319..84652419bff2 100644 --- a/Documentation/vm/slub.txt +++ b/Documentation/vm/slub.txt @@ -35,8 +35,8 @@ slub_debug=<Debug-Options>,<slab name> Enable options only for select slabs Possible debug options are - F Sanity checks on (enables SLAB_DEBUG_FREE. Sorry - SLAB legacy issues) + F Sanity checks on (enables SLAB_DEBUG_CONSISTENCY_CHECKS + Sorry SLAB legacy issues) Z Red zoning P Poisoning (object and padding) U User tracking (free and alloc) diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt index 21cf34f3ddb2..d9cb65cf5cfd 100644 --- a/Documentation/vm/transhuge.txt +++ b/Documentation/vm/transhuge.txt @@ -113,9 +113,26 @@ guaranteed, but it may be more likely in case the allocation is for a MADV_HUGEPAGE region. echo always >/sys/kernel/mm/transparent_hugepage/defrag +echo defer >/sys/kernel/mm/transparent_hugepage/defrag echo madvise >/sys/kernel/mm/transparent_hugepage/defrag echo never >/sys/kernel/mm/transparent_hugepage/defrag +"always" means that an application requesting THP will stall on allocation +failure and directly reclaim pages and compact memory in an effort to +allocate a THP immediately. This may be desirable for virtual machines +that benefit heavily from THP use and are willing to delay the VM start +to utilise them. + +"defer" means that an application will wake kswapd in the background +to reclaim pages and wake kcompact to compact memory so that THP is +available in the near future. It's the responsibility of khugepaged +to then install the THP pages later. + +"madvise" will enter direct reclaim like "always" but only for regions +that are have used madvise(MADV_HUGEPAGE). This is the default behaviour. + +"never" should be self-explanatory. + By default kernel tries to use huge zero page on read page fault. It's possible to disable huge zero page by writing 0 or enable it back by writing 1: @@ -229,6 +246,11 @@ thp_split_page is incremented every time a huge page is split into base thp_split_page_failed is is incremented if kernel fails to split huge page. This can happen if the page was pinned by somebody. +thp_deferred_split_page is incremented when a huge page is put onto split + queue. This happens when a huge page is partially unmapped and + splitting it would free up some memory. Pages on split queue are + going to be split under memory pressure. + thp_split_pmd is incremented every time a PMD split into table of PTEs. This can happen, for instance, when application calls mprotect() or munmap() on part of huge page. It doesn't split huge page, only |