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

[Jacob Martin]

On 2/2/25 9:21 AM, Heitor Alves de Siqueira wrote:
> 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(-)
> 

Acked-by: Jacob Martin <jacob.martin at canonical.com>