From: Youngjun Park <youngjun.park@lge.com>
To: Youngjun Park <her0gyugyu@gmail.com>
Cc: akpm@linux-foundation.org, chrisl@kernel.org, linux-mm@kvack.org,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
kasong@tencent.com, hannes@cmpxchg.org, mhocko@kernel.org,
roman.gushchin@linux.dev, shakeel.butt@linux.dev,
muchun.song@linux.dev, shikemeng@huaweicloud.com,
nphamcs@gmail.com, baoquan.he@linux.dev, baohua@kernel.org,
yosry@kernel.org, gunho.lee@lge.com, taejoon.song@lge.com,
hyungjun.cho@lge.com, mkoutny@suse.com, baver.bae@lge.com,
matia.kim@lge.com
Subject: Re: [PATCH v9 3/6] mm: memcontrol: add interface for swap tier selection
Date: Mon, 22 Jun 2026 14:03:13 +0900 [thread overview]
Message-ID: <ajjCEWN6IwNJLv4j@yjaykim-PowerEdge-T330> (raw)
In-Reply-To: <20260620181635.299364-4-youngjun.park@lge.com>
https://sashiko.dev/#/patchset/20260620181635.299364-1-youngjun.park@lge.com?part=3
Regarding the Sashiko review comment, I don't think this needs to be
fixed. It is acceptable for the effective_mask to be stale on a zombie
memcg.
The zombie memcg LRU is already reparented by the following patchset.
https://lore.kernel.org/all/cover.1772711148.git.zhengqi.arch@bytedance.com/
the effective_mask is only needed on the swap path. Since
swap I/O rarely (if ever) happens on a zombie memcg, leaving the stale
mask should not cause issues.
(As I mentioned above, there is no need to fix as I think.
But somehow if we needed to fix this, there would be two alternatives.
1. Fix it at offline time by setting it to SWAP_TIER_ALL_MASK. However,
this approach would break the parent tier relationship.
2. Change the memcg iteration routine to use css_for_each_descendant_pre
to explicitly handle the zombie memcg case. This approach would
safely preserve the parent tier relationship.
)
next prev parent reply other threads:[~2026-06-22 5:33 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-20 18:16 [PATCH v9 0/6] mm/swap, memcg: Introduce swap tiers for cgroup based swap control Youngjun Park
2026-06-20 18:16 ` [PATCH v9 1/6] mm: swap: introduce swap tier infrastructure Youngjun Park
2026-06-20 18:16 ` [PATCH v9 2/6] mm: swap: associate swap devices with tiers Youngjun Park
2026-06-20 18:16 ` [PATCH v9 3/6] mm: memcontrol: add interface for swap tier selection Youngjun Park
2026-06-22 5:03 ` Youngjun Park [this message]
2026-06-20 18:16 ` [PATCH v9 4/6] mm: swap: filter swap allocation by memcg tier mask Youngjun Park
2026-06-20 18:16 ` [PATCH v9 5/6] selftests/mm: add a swap tier configuration test Youngjun Park
2026-06-20 18:16 ` [PATCH v9 6/6] selftests/cgroup: add a swap tier routing test Youngjun Park
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