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| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2017-11-16 02:35:40 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-11-16 03:21:04 +0100 |
| commit | af5b0f6a09e42c9f4fa87735f2a366748767b686 (patch) | |
| tree | ac9a7992f92ae5a7902805e980bb31e8edc4555b /Documentation | |
| parent | mm: introduce wrappers to access mm->nr_ptes (diff) | |
| download | linux-af5b0f6a09e42c9f4fa87735f2a366748767b686.tar.xz linux-af5b0f6a09e42c9f4fa87735f2a366748767b686.zip | |
mm: consolidate page table accounting
Currently, we account page tables separately for each page table level,
but that's redundant -- we only make use of total memory allocated to
page tables for oom_badness calculation. We also provide the
information to userspace, but it has dubious value there too.
This patch switches page table accounting to single counter.
mm->pgtables_bytes is now used to account all page table levels. We use
bytes, because page table size for different levels of page table tree
may be different.
The change has user-visible effect: we don't have VmPMD and VmPUD
reported in /proc/[pid]/status. Not sure if anybody uses them. (As
alternative, we can always report 0 kB for them.)
OOM-killer report is also slightly changed: we now report pgtables_bytes
instead of nr_ptes, nr_pmd, nr_puds.
Apart from reducing number of counters per-mm, the benefit is that we
now calculate oom_badness() more correctly for machines which have
different size of page tables depending on level or where page tables
are less than a page in size.
The only downside can be debuggability because we do not know which page
table level could leak. But I do not remember many bugs that would be
caught by separate counters so I wouldn't lose sleep over this.
[akpm@linux-foundation.org: fix mm/huge_memory.c]
Link: http://lkml.kernel.org/r/20171006100651.44742-2-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
[kirill.shutemov@linux.intel.com: fix build]
Link: http://lkml.kernel.org/r/20171016150113.ikfxy3e7zzfvsr4w@black.fi.intel.com
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/filesystems/proc.txt | 1 | ||||
| -rw-r--r-- | Documentation/sysctl/vm.txt | 8 |
2 files changed, 4 insertions, 5 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index adba21b5ada7..ec571b9bb18a 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -250,7 +250,6 @@ Table 1-2: Contents of the status files (as of 4.8) VmExe size of text segment VmLib size of shared library code VmPTE size of page table entries - VmPMD size of second level page tables VmSwap amount of swap used by anonymous private data (shmem swap usage is not included) HugetlbPages size of hugetlb memory portions diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index 2729e8db9492..3e579740b49f 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -629,10 +629,10 @@ oom_dump_tasks Enables a system-wide task dump (excluding kernel threads) to be produced when the kernel performs an OOM-killing and includes such information as -pid, uid, tgid, vm size, rss, nr_ptes, nr_pmds, nr_puds, swapents, -oom_score_adj score, and name. This is helpful to determine why the OOM -killer was invoked, to identify the rogue task that caused it, and to -determine why the OOM killer chose the task it did to kill. +pid, uid, tgid, vm size, rss, pgtables_bytes, swapents, oom_score_adj +score, and name. This is helpful to determine why the OOM killer was +invoked, to identify the rogue task that caused it, and to determine why +the OOM killer chose the task it did to kill. If this is set to zero, this information is suppressed. On very large systems with thousands of tasks it may not be feasible to dump |