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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1755099909; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=SsPDwhSTBJoReLg/9/YKJlevSdDByn1CpS92UikRLrs=; b=EprmuzHOFgXR6T/Un4d8FyvdxlSvFwXlSh+XmMWLyARs9/QurDnM9B2l748u+jSFn+YVu5 cGeYlgobVLC9l02O58aMzTZc3Sc8TbqTVd31gv7iOf2l5w06YraQo1dkybNq4ipvKctMRC XXUItOdleZVof38aYxrbhvgEPK93qX8= From: Roman Gushchin To: Thomas Gleixner Cc: linux-mm@kvack.org, LKML , Peter Zijlstra , Johannes Weiner , Michal Hocko , Shakeel Butt , Muchun Song , cgroups@vger.kernel.org, Andrew Morton Subject: Re: [PATCH] memcg: Optimize exit to user space In-Reply-To: <87tt2b6zgs.ffs@tglx> (Thomas Gleixner's message of "Wed, 13 Aug 2025 16:57:55 +0200") References: <87tt2b6zgs.ffs@tglx> Date: Wed, 13 Aug 2025 08:45:02 -0700 Message-ID: <87ectfgr9d.fsf@linux.dev> MIME-Version: 1.0 Content-Type: text/plain X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: B93BE2000E X-Rspamd-Server: rspam06 X-Stat-Signature: 749ndb3zoqymha1hh3u1ggpizsufgynw X-HE-Tag: 1755099911-50593 X-HE-Meta: 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 fPivFYy5 KMEez3D64yE6PcGEzUtpu1JHKcrw35qAe5KDEzSWQp5nqOVz47EE5f2gwgzRZlCM7HT3MJ0YlVFH5RSxA8YLUm/S5f941TT1ukXwHRRP900BmnuNwbwq3K/qXoZ/b8PujM5z+/QO6Qutb3Kqf75HUcMKsdZa161uJCAlFrUMSh7RXzfCetze00i1KlZrBsrHbfWKBnAIz4dN4qQiSLwRwO3bAExmJ6+fcBpzl21BwJwSw1b6uuJaErFluXt5ncMLyoNYWeoWzRMbOFQ9Qv9xUdA54z8b8UGUwMEuL7aIZT65J7Rs= 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: List-Subscribe: List-Unsubscribe: Thomas Gleixner writes: > memcg uses TIF_NOTIFY_RESUME to handle reclaiming on exit to user > space. TIF_NOTIFY_RESUME is a multiplexing TIF bit, which is utilized by > other entities as well. > > This results in a unconditional mem_cgroup_handle_over_high() call for > every invocation of resume_user_mode_work(), which is a pointless > exercise as most of the time there is no reclaim work to do. > > Especially since RSEQ is used by glibc, TIF_NOTIFY_RESUME is raised > quite frequently and the empty calls show up in exit path profiling. > > Optimize this by doing a quick check of the reclaim condition before > invoking it. > > Signed-off-by: Thomas Gleixner > Cc: Johannes Weiner > Cc: Michal Hocko > Cc: Roman Gushchin > Cc: Shakeel Butt > Cc: Muchun Song > Cc: Andrew Morton Reviewed-by: Roman Gushchin Thanks!