From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.31 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793407610; b=1Mbw0zoj1WYO8TNSn13bK1T8eCrUFsxh+nSEoPAlEDKXy8Kd7FBH/FDiddZJPuYUZ1RI yxGDPQKGryH1D7AariiVNNRcEaN4R2bkeFEO7K0wQEO/aNsBCDmmwms4qFe7rcXz54e7j CdZvPDQt3jqq5hYje/PClc0TlB9z6ibnTCHB0y26nIqlpNdS4a5d8ZRHFxSXLNrvcTMSe rcIfYIcCIqtvnodOA9lwBEjnPlOB8MLVE4fuRrPWFcZf07E3vFhlHPwo7wzjy358Zc+vO 5P3LaBFOcojiS4dZEcjbORly9AVKgLBG1jaV6gBfIUZHyqt2cDatr2aAl73NP3U/G6Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793407610; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:Content-Type:Mime-Version:Subject:From: In-Reply-To:Date:Cc:Content-Transfer-Encoding:Message-Id:References: To:X-Mailer; bh=H7Ifc7p7cHcO1C78lzF+gI6I9rOcTVWv5sLtNAQ1MO0=; b=XwpE/nAaZGvI5g0RJs6UbVxYouwExNcJjyhgn0HWSNLFAoA8Kwn9yEXb/qVerZvHYO+w 1+/ZYAmLBKAxbbv0ha/dOYU78Dx7U+zlI/+lptqAIDO059ek9LXWi4fdwQ/grina9gOWB aufJGGBv2nsahAzr7ZkPH6DOXxJeQpihCDqqSreBCVG9vUu9nR4rdFpaxq+ntlJNaYUOf kKkWkBmSxypEMVrlMPeKFRi1fPQ0FGTzVhXwpLE4nna/Ghhc6yv021keWzMsPK5rJNbIH Xja37/4lgfhCb17SYPSAPnA9OFn3BW0i+9jqU96OKG0yCZefOQiPoYNiGU3eH4Xg9rg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=StOVEISL; arc=none smtp.remote-ip=95.215.58.31 Received: from mta1.migadu.com (out-31.mta1.migadu.com [95.215.58.31]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 87488606A31C for ; Sat, 31 Oct 2026 00:46:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 87488606A31C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=StOVEISL X-Envelope-To: cgroups@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=z26c2PyZ8pF8QGqqT2YXQEk7jdeK6dxDZwh05tv1Xdw=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793407607; v=1; x=1794012407; b=StOVEISLs7OTCFFflGvKw3SGY3u0LB+qtHOZoYHM907Qe2I2bliBtIMwaVx+X9XV9oDdZhX6 bLwv6fhv4B1GGNxmjaxcHbXmWHIqDa5viGyTJEQjrRnrO5qvYvuTCDBPgdIRpYdqow2OdTTLZpP UT8a7Gr/3H22m/GTp4QsGiEY= X-Envelope-To: cgroups@vger.kernel.org Received: by mta10.migadu.com with ESMTPS id 619347082113727e; Sat, 31 Oct 2026 00:46:47 +0000 X-Mizu-Trace-ID: 619347082113727e X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=us-ascii X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3901.100.1.1.12\)) Subject: Re: [PATCH v2 2/5] memcg: force charges from reclaim before trying the limits From: Muchun Song In-Reply-To: <20261030205418.341214-3-shakeel.butt@linux.dev> Date: Sat, 31 Oct 2026 08:46:31 +0800 Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Tejun Heo , Harry Yoo , Meta kernel team , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko Content-Transfer-Encoding: 7bit Message-Id: <7CE7A687-C45B-4F99-8F58-88633E052D85@linux.dev> References: <20261030205418.341214-1-shakeel.butt@linux.dev> <20261030205418.341214-3-shakeel.butt@linux.dev> To: Shakeel Butt X-Mailer: Apple Mail (2.3901.100.1.1.12) > On Oct 31, 2026, at 04:54, Shakeel Butt wrote: > > Reclaim can charge memory, for example when zswap stores a page. > try_charge_memcg() forces these PF_MEMALLOC charges, but only after > they fail at a limit. A charge that fits still has memory.high > enforced. That can make a task in direct reclaim do more reclaim and > sleep longer later, and kswapd records overage that it never handles. > > It is also a problem for the next patches, which make kernel threads > queue high_work. The worker charges memory from its own reclaim, so it > can queue itself again. With those patches but not this one, the worker > queued itself in 118 of 284 runs in a VM test with incompressible zswap > data. > > Check PF_MEMALLOC before trying the limits. Reclaim charges then skip > memory.high, as they can already go over memory.max. Drop the > PF_MEMALLOC check in memcg_enforce_high(), which no longer sees them. > > Other effects: > - As before, the check reads current, so it also catches interrupts on > a PF_MEMALLOC task such as kswapd. Softirqs set PF_MEMALLOC > themselves for swap over network, so the check can't be limited to > task context. > - These charges no longer charge a batch or refill the per-cpu stock. > - MEMCG_MAX still goes to the first cgroup that the charge puts over > its limit. On cgroup v1, memory.failcnt no longer counts them. > - high_work can still run again and again when there is nothing left > to reclaim. This only stops reclaim from queuing more reclaim. > > Suggested-by: Michal Hocko > Signed-off-by: Shakeel Butt Acked-by: Muchun Song Thanks.