Re: [PATCH v3 0/4] mm: restore per-memcg reclaim for NONSLAB shrinkers under nokmem

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 10 Sep 2026 16:07:18 +0800 Qinyun Tan <qinyuntan@linux.alibaba.com> wrote:

> With cgroup.memory=nokmem, the THP deferred split shrinker and the
> zswap shrinker are degraded in two ways.
> 
> First, both shrinkers are missing the SHRINKER_NONSLAB flag, so
> shrinker_memcg_alloc() demotes them to non-memcg-aware shrinkers:
> limit-induced reclaim of a cgroup neither splits its partially
> unmapped THPs nor writes back its zswapped pages.  v1 of this series
> [1] restored the flag to fix that.
> 
> However, as Sashiko's review of v1 pointed out [2], the flag alone
> is not enough.  __list_lru_init() also collapses every list_lru into
> per-node lists under nokmem, so even with the flag restored, the
> objects of all cgroups share one list per node: the per-memcg
> shrinker bit is only set for whichever memcg happens to repopulate
> the empty list, so pressure in other cgroups may not even trigger
> the scan, and when it does, the scan walks everyone's objects.
> 
> Before commit fafaeceb89a5 ("mm: switch deferred split shrinker to
> list_lru"), THP had fully per-memcg deferred split queues embedded
> in struct mem_cgroup, working independently of kmem accounting.
> nokmem only opts out of kernel slab accounting; THPs and zswapped
> pages are user memory and remain charged to their cgroups, so
> per-memcg reclaim is still what these shrinkers want.
> 
> This series keeps list_lrus backed by SHRINKER_NONSLAB shrinkers
> memcg aware under nokmem:

Thanks.

It seems that Sashiko still doesn't understand that memory allocations
in __init code are considered "can't fail".

	https://sashiko.dev/#/patchset/20260910080722.3961351-1-qinyuntan@linux.alibaba.com

otoh, failures in the functiond which hugepage_init() calls might be
caused by things other than ENOMEM so I guess we shouldn't zap all that
cleanup code.

Anyway, that's unrelated to your changes.

I'll save this patchset away for later and shall await reviewer input. 
Please poke me in a week or so if there hasn't been any, Things are
crazy lately.