[SRU][N/O/P][PATCH 0/1] MGLRU: page allocation failure on NUMA-enabled systems

[Heitor Alves de Siqueira]

BugLink: https://bugs.launchpad.net/bugs/2097214

[Impact]
 * On MGLRU-enabled systems, high memory pressure on NUMA nodes will cause page
   allocation failures
 * This happens due to page reclaim not waking up flusher threads
 * OOM can be triggered even if the system has enough available memory

[Test Plan]
 * For the bug to properly trigger, we should uninstall apport and use the
   attached alloc_and_crash.c reproducer
 * alloc_and_crash will mmap a huge range of memory, memset it and forcibly SEGFAULT
 * The attached bash script will membind alloc_and_crash to NUMA node 0, so we
   can see the allocation failures in dmesg
   $ sudo apt remove --purge apport
   $ sudo dmesg -c; ./lp2097214-repro.sh; sleep 2; sudo dmesg

[Fix]
 * The upstream patch wakes up flusher threads if there are too many dirty
   entries in the coldest LRU generation
 * This happens when trying to shrink lruvecs, so reclaim only gets woken up
   during high memory pressure
 * Fix was introduced by commit:
     1bc542c6a0d1 mm/vmscan: wake up flushers conditionally to avoid cgroup OOM

[Regression Potential]
 * This commit fixes the memory reclaim path, so regressions would likely show
   up during increased system memory pressure
 * According to the upstream patch, increased SSD/disk wearing is possible due
   to waking up flusher threads, although these have not been noted in testing

Zeng Jingxiang (1):
  mm/vmscan: wake up flushers conditionally to avoid cgroup OOM

 mm/vmscan.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

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2.48.1