From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Hui Zhu <hui.zhu@linux.dev>
Cc: Minchan Kim <minchan@kernel.org>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
teawater <zhuhui@kylinos.cn>
Subject: Re: [PATCH] zsmalloc: return -EAGAIN for zspage migration lock contention
Date: Wed, 18 Mar 2026 19:21:48 +0900 [thread overview]
Message-ID: <abp7HJRZQi35wHn-@google.com> (raw)
In-Reply-To: <20260318073114.34858-1-hui.zhu@linux.dev>
On (26/03/18 15:31), Hui Zhu wrote:
> movable_operations::migrate_page() should return -EAGAIN for temporary
> migration failures so the migration core can retry. Other negative
> errors are treated as permanent failures.
>
> zs_page_migrate() currently returns -EINVAL when zspage_write_trylock()
> fails. That path reflects transient lock contention, not invalid input.
> Returning -EINVAL misclassifies the failure and can reduce migration
> success under contention.
The zspage's reader-lock owner can be preempted for unknown duration,
so I don't know if returning -EAGAIN is safe. On one hand, migration
attempts are limited by NR_MAX_MIGRATE_PAGES_RETRY, on the other hand,
those attempts are performed basically immediately (?), I'm not sure
if we have good chances for preempted reader-lock owner to get scheduled
and release the lock in time.
next prev parent reply other threads:[~2026-03-18 10:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-18 7:31 [PATCH] zsmalloc: return -EAGAIN for zspage migration lock contention Hui Zhu
2026-03-18 10:21 ` Sergey Senozhatsky [this message]
2026-03-18 10:31 ` Sergey Senozhatsky
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