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Thu, 03 Sep 2026 06:03:09 -0700 (PDT) Date: Thu, 3 Sep 2026 09:03:04 -0400 From: Johannes Weiner To: Bo Zhang Cc: akpm@linux-foundation.org, kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, david@kernel.org, mhocko@kernel.org, ljs@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Bo Zhang Subject: Re: [RFC PATCH] mm: vmscan: avoid anon scanning for GFP_NOIO with low swapcache Message-ID: <20260903130304.GQ3004@cmpxchg.org> References: <20260903040131.4016290-1-zhangbo56@xiaomi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260903040131.4016290-1-zhangbo56@xiaomi.com> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: E2E2C14000B X-Stat-Signature: 7yzzfygoe49sk796esjcp4guqicsoic4 X-HE-Tag: 1788440591-244793 X-HE-Meta: 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 BlMomAUf KG10SAu8zQuvoae7Ly09fIzyYTD8uyu/tYMHjpZP2+xKOaLoJvR7L/ZeCjbPl81sSgOaeCK9sN/KoxvfYdJ2oSoaD7fLQ4SqDm7KILYrDbU+zs9KtwImOalmY8qj2L0PVEFGejxoHNGh7N+mH6n9T6Ub8WnXD6Hv4fiHIO+ZEshJfa2arPUYSlndpawYXNZgkMvIobdw5nMdxKfAGimVONRYOO+H803JqP8pVnmxVcuk8tQStUq5W6YuflZ5zna9oUNklLG+V/+pUjCVjc/mKzwxFs51Omy0vtNP8M0Nkx/epauVKM3uG+ygaxqI+cWRc/4+F/MrkAlGWffi7oI6ZBZ8Zco6WD+wCMF3MNajhbp1WSkj+LAj1Ihr9YwHef+KmXKlT4u2hGlJKVprsKbpxS6MGuvgiLyW16Mz0YCJ/FlB3lg0oHhQ3GHg381UCJhhQmtd3WAFC/XmNBxo= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Sep 03, 2026 at 12:01:31PM +0800, Bo Zhang wrote: > We have observed some cases where memory is allocated with GFP_NOIO, so > we cannot reclaim any anon folios unless they are in swapcache. We can > end up spending more than 150 ms looping in `shrink_folio_list()` scanning > non-swapcache folios without reclaiming a single folio. This is pure > overhead. Not entirely. There is some value in aging anon alongside file, so that the next __GFP_IO reclaimer doesn't look at a stale list. Can you describe a bit more about what you observed? What workload is running, maybe you have a stack trace of which NOIO requests are routinely getting stuck in reclaim? 150ms sounds awful indeed. Is this cumulative for a whole reclaim cycle or single shrink_folio_list() runs?