From: Johannes Weiner <hannes@cmpxchg.org>
To: Kinsey Ho <kinseyho@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Yosry Ahmed <yosryahmed@google.com>,
Roman Gushchin <roman.gushchin@linux.dev>
Subject: Re: [PATCH mm-unstable v1 2/4] mm: increment gen # before restarting traversal
Date: Thu, 25 Jul 2024 16:53:34 -0400 [thread overview]
Message-ID: <20240725205334.GB1702603@cmpxchg.org> (raw)
In-Reply-To: <20240724190214.1108049-3-kinseyho@google.com>
On Wed, Jul 24, 2024 at 07:02:12PM +0000, Kinsey Ho wrote:
> The generation number in struct mem_cgroup_reclaim_iter should be
> incremented on every round-trip. Currently, it is possible for a
> concurrent reclaimer to jump in at the end of the hierarchy, causing a
> traversal restart (resetting the iteration position) without
> incrementing the generation number.
>
> Move the traversal restart such that the generation number is
> incremented before the restart.
>
> Signed-off-by: Kinsey Ho <kinseyho@google.com>
The consequence of resetting the position without bumping the
generation would be that another ongoing mem_cgroup_iter() could walk
the tree twice, which is undesirable. It would be good to spell that
out in the changelog.
Otherwise, looks good to me.
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
next prev parent reply other threads:[~2024-07-25 20:53 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-24 19:02 [PATCH mm-unstable v1 0/4] Improve mem_cgroup_iter() Kinsey Ho
2024-07-24 19:02 ` [PATCH mm-unstable v1 1/4] mm: don't hold css->refcnt during traversal Kinsey Ho
2024-07-25 16:33 ` kernel test robot
2024-07-25 20:43 ` Johannes Weiner
2024-07-25 21:09 ` Roman Gushchin
2024-07-25 22:33 ` Yosry Ahmed
2024-08-01 21:46 ` Kinsey Ho
2024-08-01 22:32 ` Kinsey Ho
2024-08-02 1:28 ` Johannes Weiner
2024-07-24 19:02 ` [PATCH mm-unstable v1 2/4] mm: increment gen # before restarting traversal Kinsey Ho
2024-07-25 20:53 ` Johannes Weiner [this message]
2024-07-24 19:02 ` [PATCH mm-unstable v1 3/4] mm: restart if multiple traversals raced Kinsey Ho
2024-07-24 19:02 ` [PATCH mm-unstable v1 4/4] mm: clean up mem_cgroup_iter() Kinsey Ho
2024-07-25 18:15 ` kernel test robot
2024-07-25 0:25 ` [PATCH mm-unstable v1 0/4] Improve mem_cgroup_iter() Roman Gushchin
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