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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qq3sc-002HYA-JP; Tue, 10 Oct 2023 03:57:58 +0000 Date: Tue, 10 Oct 2023 04:57:58 +0100 From: Matthew Wilcox To: Bin Lai Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, akpm@linux-foundation.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Bin Lai Subject: Re: [PATCH] sched/wait: introduce endmark in __wake_up_common Message-ID: References: <20231010032833.398033-1-robinlai@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231010032833.398033-1-robinlai@tencent.com> X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 3BE054000A X-Stat-Signature: yedhbipdspa9nxedtw9ky9w4pupnxokj X-HE-Tag: 1696910302-799184 X-HE-Meta: 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 XLJmErMM SwE4rYXlBusBvnm97A7/I7bvAmJbQoDxyTkBdHdIp0lJj+JyAaXEbe2RtGeG9M1lNmaq7B2DsuNqsKNTg30G61DJGAjpxXU7Ic61CmR+fuHLMNh9n0X/U1jmvH6GF2kPGVC/GVeYTSiWvJ/mxZFcgtsXZDfV4uzj0TvlWIwAetcp/EyXiIk+P16BvwQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Oct 10, 2023 at 11:28:33AM +0800, Bin Lai wrote: > Without this patch applied, it can cause the waker to fall into an > infinite loop in some cases. The commit 2554db916586 ("sched/wait: Break > up long wake list walk") introduces WQ_FLAG_BOOKMARK to break up long > wake list walk. When the number of walked entries reach 64, the waker > will record scan position and release the queue lock, which reduces > interrupts and rescheduling latency. Maybe we could try removing bookmarks instead? There was a thread a while ago where we agreed they weren't actually useful any more. Patches to follow ...