Commit 39799b64 authored by Johannes Weiner's avatar Johannes Weiner Committed by Andrew Morton
Browse files

Documentation: filesystems: proc: update meminfo section 

Patch series "zswap: accounting & cgroup control", v2.

Zswap can consume nearly a quarter of RAM in the default configuration,
yet it's neither listed in /proc/meminfo, nor is it accounted and
manageable on a per-cgroup basis.

This makes reasoning about the memory situation on a host in general
rather difficult.  On shared/cgrouped hosts, the consequences are worse. 
First, workloads can escape memory containment and cause resource priority
inversions: a lo-pri group can fill the global zswap pool and force a
hi-pri group out to disk.  Second, not all workloads benefit from zswap
equally.  Some even suffer when memory contents compress poorly, and are
better off going to disk swap directly.  On a host with mixed workloads,
it's currently not possible to enable zswap for one workload but not for
the other.

This series implements the missing global accounting as well as cgroup
tracking & control for zswap backing memory:

- Patch 1 refreshes the very out-of-date meminfo documentation in
  Documentation/filesystems/proc.rst.

- Patches 2-4 clean up related and adjacent options in Kconfig. Not
  actual dependencies, just things I noticed during development.

- Patch 5 adds meminfo and vmstat coverage for zswap consumption and
  activity.

- Patch 6 implements per-cgroup tracking & control of zswap memory.


This patch (of 6):

Add new entries.  Minor corrections and cleanups.

[hannes@cmpxchg.org: fix htmldocs warnings]
  Link: https://lkml.kernel.org/r/Ynve8dg4zJyhH2gW@cmpxchg.org
[hannes@cmpxchg.org: change `Unevictable' wording, per David]
  Link: https://lkml.kernel.org/r/YnwFraZlVWQoCjz3@cmpxchg.org
Link: https://lkml.kernel.org/r/20220510152847.230957-1-hannes@cmpxchg.org
Link: https://lkml.kernel.org/r/20220510152847.230957-2-hannes@cmpxchg.org


Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent ff351f4b

Documentation/filesystems/proc.rst

+92 −56
Original line number Diff line number Diff line
@@ -942,56 +942,71 @@ can be substantial. In many cases there are other means to find out 
additional memory using subsystem specific interfaces, for instance

/proc/net/sockstat for TCP memory allocations.



The following is from a 16GB PIII, which has highmem enabled.

You may not have all of these fields.

Example output. You may not have all of these fields.



::



    > cat /proc/meminfo



    MemTotal:     16344972 kB

    MemFree:      13634064 kB

    MemAvailable: 14836172 kB

    Buffers:          3656 kB

    Cached:        1195708 kB

    MemTotal:       32858820 kB

    MemFree:        21001236 kB

    MemAvailable:   27214312 kB

    Buffers:          581092 kB

    Cached:          5587612 kB

    SwapCached:            0 kB

    Active:         891636 kB

    Inactive:      1077224 kB

    HighTotal:    15597528 kB

    HighFree:     13629632 kB

    LowTotal:       747444 kB

    LowFree:          4432 kB

    Active:          3237152 kB

    Inactive:        7586256 kB

    Active(anon):      94064 kB

    Inactive(anon):  4570616 kB

    Active(file):    3143088 kB

    Inactive(file):  3015640 kB

    Unevictable:           0 kB

    Mlocked:               0 kB

    SwapTotal:             0 kB

    SwapFree:              0 kB

    Dirty:             968 kB

    Dirty:                12 kB

    Writeback:             0 kB

    AnonPages:      861800 kB

    Mapped:         280372 kB

    Shmem:             644 kB

    KReclaimable:   168048 kB

    Slab:           284364 kB

    SReclaimable:   159856 kB

    SUnreclaim:     124508 kB

    PageTables:      24448 kB

    AnonPages:       4654780 kB

    Mapped:           266244 kB

    Shmem:              9976 kB

    KReclaimable:     517708 kB

    Slab:             660044 kB

    SReclaimable:     517708 kB

    SUnreclaim:       142336 kB

    KernelStack:       11168 kB

    PageTables:        20540 kB

    NFS_Unstable:          0 kB

    Bounce:                0 kB

    WritebackTmp:          0 kB

    CommitLimit:   7669796 kB

    Committed_AS:   100056 kB

    VmallocTotal:   112216 kB

    VmallocUsed:       428 kB

    VmallocChunk:   111088 kB

    Percpu:          62080 kB

    CommitLimit:    16429408 kB

    Committed_AS:    7715148 kB

    VmallocTotal:   34359738367 kB

    VmallocUsed:       40444 kB

    VmallocChunk:          0 kB

    Percpu:            29312 kB

    HardwareCorrupted:     0 kB

    AnonHugePages:   49152 kB

    AnonHugePages:   4149248 kB

    ShmemHugePages:        0 kB

    ShmemPmdMapped:        0 kB

    FileHugePages:         0 kB

    FilePmdMapped:         0 kB

    CmaTotal:              0 kB

    CmaFree:               0 kB

    HugePages_Total:       0

    HugePages_Free:        0

    HugePages_Rsvd:        0

    HugePages_Surp:        0

    Hugepagesize:       2048 kB

    Hugetlb:               0 kB

    DirectMap4k:      401152 kB

    DirectMap2M:    10008576 kB

    DirectMap1G:    24117248 kB



MemTotal

              Total usable RAM (i.e. physical RAM minus a few reserved

              bits and the kernel binary code)

MemFree

              The sum of LowFree+HighFree

              Total free RAM. On highmem systems, the sum of LowFree+HighFree

MemAvailable

              An estimate of how much memory is available for starting new

              applications, without swapping. Calculated from MemFree,
@@ -1005,8 +1020,9 @@ Buffers 
              Relatively temporary storage for raw disk blocks

              shouldn't get tremendously large (20MB or so)

Cached

              in-memory cache for files read from the disk (the

              pagecache).  Doesn't include SwapCached

              In-memory cache for files read from the disk (the

              pagecache) as well as tmpfs & shmem.

              Doesn't include SwapCached.

SwapCached

              Memory that once was swapped out, is swapped back in but

              still also is in the swapfile (if memory is needed it
@@ -1018,6 +1034,11 @@ Active 
Inactive

              Memory which has been less recently used.  It is more

              eligible to be reclaimed for other purposes

Unevictable

              Memory allocated for userspace which cannot be reclaimed, such

              as mlocked pages, ramfs backing pages, secret memfd pages etc.

Mlocked

              Memory locked with mlock().

HighTotal, HighFree

              Highmem is all memory above ~860MB of physical memory.

              Highmem areas are for use by userspace programs, or
@@ -1040,20 +1061,10 @@ Writeback 
              Memory which is actively being written back to the disk

AnonPages

              Non-file backed pages mapped into userspace page tables

HardwareCorrupted

              The amount of RAM/memory in KB, the kernel identifies as

	      corrupted.

AnonHugePages

              Non-file backed huge pages mapped into userspace page tables

Mapped

              files which have been mmaped, such as libraries

Shmem

              Total memory used by shared memory (shmem) and tmpfs

ShmemHugePages

              Memory used by shared memory (shmem) and tmpfs allocated

              with huge pages

ShmemPmdMapped

              Shared memory mapped into userspace with huge pages

KReclaimable

              Kernel allocations that the kernel will attempt to reclaim

              under memory pressure. Includes SReclaimable (below), and other
@@ -1064,9 +1075,10 @@ SReclaimable 
              Part of Slab, that might be reclaimed, such as caches

SUnreclaim

              Part of Slab, that cannot be reclaimed on memory pressure

KernelStack

              Memory consumed by the kernel stacks of all tasks

PageTables

              amount of memory dedicated to the lowest level of page

              tables.

              Memory consumed by userspace page tables

NFS_Unstable

              Always zero. Previous counted pages which had been written to

              the server, but has not been committed to stable storage.
@@ -1107,7 +1119,7 @@ Committed_AS 
              not fail due to lack of memory once that memory has been

              successfully allocated.

VmallocTotal

              total size of vmalloc memory area

              total size of vmalloc virtual address space

VmallocUsed

              amount of vmalloc area which is used

VmallocChunk
@@ -1115,6 +1127,30 @@ VmallocChunk 
Percpu

              Memory allocated to the percpu allocator used to back percpu

              allocations. This stat excludes the cost of metadata.

HardwareCorrupted

              The amount of RAM/memory in KB, the kernel identifies as

              corrupted.

AnonHugePages

              Non-file backed huge pages mapped into userspace page tables

ShmemHugePages

              Memory used by shared memory (shmem) and tmpfs allocated

              with huge pages

ShmemPmdMapped

              Shared memory mapped into userspace with huge pages

FileHugePages

              Memory used for filesystem data (page cache) allocated

              with huge pages

FilePmdMapped

              Page cache mapped into userspace with huge pages

CmaTotal

              Memory reserved for the Contiguous Memory Allocator (CMA)

CmaFree

              Free remaining memory in the CMA reserves

HugePages_Total, HugePages_Free, HugePages_Rsvd, HugePages_Surp, Hugepagesize, Hugetlb

              See Documentation/admin-guide/mm/hugetlbpage.rst.

DirectMap4k, DirectMap2M, DirectMap1G

              Breakdown of page table sizes used in the kernel's

              identity mapping of RAM



vmallocinfo

~~~~~~~~~~~