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Subject[RFC v2] oom: capture unreclaimable slab info in oom message when kernel panic

Sorry, forgot send the cover letter with change log. Resent the patch series.

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 v1 —> v2:
* Removed the original patch 1 (“mm: slab: output reclaimable flag in /proc/slabinfo”) since Christopher suggested it might break the compatibility and /proc/slabinfo is legacy
* Added Christopher’s Acked-by
* Removed acquiring slab_mutex per Tetsuo’s comment

Yang Shi (2):
tools: slabinfo: add "-U" option to show unreclaimable slabs only
mm: oom: show unreclaimable slab info when kernel panic

mm/oom_kill.c | 13 +++++++++++--
mm/slab.c | 1 +
mm/slab.h | 7 +++++++
mm/slab_common.c | 30 ++++++++++++++++++++++++++++++
mm/slub.c | 1 +
tools/vm/slabinfo.c | 11 ++++++++++-
6 files changed, 60 insertions(+), 3 deletions(-)

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