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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260903040131.4016290-1-zhangbo56@xiaomi.com> 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?