[PATCH 0/3 v10] oom: capture unreclaimable slab info in oom message

From: Yang Shi
Date: Wed Oct 04 2017 - 17:29:33 EST

Recently we ran into a oom issue, kernel panic due to no killable process.
The dmesg shows huge unreclaimable slabs used almost 100% memory, but kdump doesn't capture vmcore due to some reason.

So, it may sound better to capture unreclaimable slab info in oom message when kernel panic to aid trouble shooting and cover the corner case.
Since kernel already panic, so capturing more information sounds worthy and doesn't bother normal oom killer.

With the patchset, tools/vm/slabinfo has a new option, "-U", to show unreclaimable slab only.

And, oom will print all non zero (num_objs * size != 0) unreclaimable slabs in oom killer message.

For details, please see the commit log for each commit.

Changelog v9 â> v10:
* Adopted the suggestion from Michal to just dump unreclaimable slab stats when !is_memcg_oom
* Adopted the suggestion from Michal to print warning when unreclaimable slabs dump canât acquire the mutex

Changelog v8 â> v9:
* Adopted Tetsuoâs suggestion to protect global slab list traverse with mutex_trylock() to prevent from sleeping. Without the mutex acquired unreclaimable slbas will not be dumped.
* Adopted the suggestion from Christoph to dump CONFIG_SLABINFO since it is pointless to keep it.
* Rebased to 4.13-rc3

Changelog v7 â> v8:
* Adopted Michalâs suggestion to dump unreclaim slab info when unreclaimable slabs amount > total user memory. Not only in oom panic path.

Changelog v6 -> v7:
* Added unreclaim_slabs_oom_ratio proc knob, unreclaimable slabs info will be dumped when unreclaimable slabs amount : all user memory > the ratio

Changelog v5 â> v6:
* Fixed a checkpatch.pl warning for patch #2

Changelog v4 â> v5:
* Solved the comments from David
* Build test SLABINFO = n

Changelog v3 â> v4:
* Solved the comments from David
* Added Davidâs Acked-by in patch 1

Changelog v2 â> v3:
* Show used size and total size of each kmem cache per Davidâs comment

Changelog v1 â> v2:
* Removed the original patch 1 (âmm: slab: output reclaimable flag in /proc/slabinfoâ) since Christoph suggested it might break the compatibility and /proc/slabinfo is legacy
* Added Christophâs Acked-by
* Removed acquiring slab_mutex per Tetsuoâs comment

Yang Shi (3):
tools: slabinfo: add "-U" option to show unreclaimable slabs only
mm: slabinfo: dump CONFIG_SLABINFO
mm: oom: show unreclaimable slab info when unreclaimable slabs > user memory

init/Kconfig | 6 ------
mm/memcontrol.c | 2 --
mm/oom_kill.c | 27 +++++++++++++++++++++++++--
mm/slab.c | 2 --
mm/slab.h | 2 ++
mm/slab_common.c | 38 +++++++++++++++++++++++++++++++++++---
mm/slub.c | 2 --
tools/vm/slabinfo.c | 11 ++++++++++-
8 files changed, 72 insertions(+), 18 deletions(-)