From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.33 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793407610; b=FvAaU1qLMNfYCgXwib+FohHORMQ7I328EysUf3Q6qHOFMeA97MdAJXFsunv6ftvAVywF 8z5GXfjYyyo/Uc+ZGGJ4S2DVExF50rZdO7xHak2GE9H8FoUAJ7WWV1Lfv2DIZYzWA2uih c1XxNPoDqhN8SZa7zohzSrxeC4BYcQr/O2jMt1pqKhzrTPleTtEHEQf9mUNbmimFDjOMk J+ZOpVFwZCCpIJMOzFbEdczRjfAel9GnjI7BfiahACBCZffqn+f/s+LW1lRI88QByRdPe WccVi/TW1dl6D+kxrrXjj6sV5ofKR1VSIsNlwDhaCmD8HtZmcGFrU1yh6pYNicFN1Tw== 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=kg3zI6hx9Rwz09mBnPXjaEP21p8MguWftbOuLZywRpsdPF5xbltEu+TRwS1tuLpq4ZiD qDdnxcN/L1YXZrGxEGzZAvUXkigiQAu8Y8hUTYMMGKOvK/Y14Xu181RtoVLSq3jMFar47 KWiWQTRbkx1TJ5L8nt9kPOpEsIpgga/nPj1eESirv4gYgDMMcvxixiJfRoS4+uR4K0pmg 73cJIHyuT+b3Ff/uCRxr81/9hbvkJZlhM69IWCei5KDPDWGKzAr6xLNKriNR1k80UqiqA JjuwZiAtAfDxucakbU7N/tsBrmnxeiZhtMhOvoc8x6bJpoU7LeiEnEVQefCMwWZRkVg== 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=95.215.58.33 Received: from mta1.migadu.com (out-33.mta1.migadu.com [95.215.58.33]) (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 820EB606A31A for ; Sat, 31 Oct 2026 00:46:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 820EB606A31A 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: linux-kernel@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: linux-kernel@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: linux-kernel@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.