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[54.240.9.30]) by mx.google.com with ESMTPS id p67si650813qkd.272.2019.03.22.12.39.31 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 22 Mar 2019 12:39:31 -0700 (PDT) Received-SPF: pass (google.com: domain of 01000169a6ea5e46-f845b8db-730b-436e-980c-3e4273ad2e34-000000@amazonses.com designates 54.240.9.30 as permitted sender) client-ip=54.240.9.30; Authentication-Results: mx.google.com; dkim=pass header.i=@amazonses.com header.s=6gbrjpgwjskckoa6a5zn6fwqkn67xbtw header.b=iT0HBMtB; spf=pass (google.com: domain of 01000169a6ea5e46-f845b8db-730b-436e-980c-3e4273ad2e34-000000@amazonses.com designates 54.240.9.30 as permitted sender) smtp.mailfrom=01000169a6ea5e46-f845b8db-730b-436e-980c-3e4273ad2e34-000000@amazonses.com DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple; s=6gbrjpgwjskckoa6a5zn6fwqkn67xbtw; d=amazonses.com; t=1553283571; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References:MIME-Version:Content-Type:Feedback-ID; bh=+QFmd+qhN2DLA1/sywGPwInOJrjDW1Q9BEXsX4YZ2II=; b=iT0HBMtBFw2zX7vPdC/3Hsd9GGDeJyPy6RlxeEJUJszYMDjDulBgegdH876HD3qC BOgjqXiznIZnV3+Sj6z/nBaQCINjevkXajnbsdePLIenCSkdZj3ReRNlcgKJsKNchHb LLL7D9EhkY/3zv0B+S6iFEINleSK1wksxGKy3K9Y= Date: Fri, 22 Mar 2019 19:39:31 +0000 From: Christopher Lameter X-X-Sender: cl@nuc-kabylake To: Waiman Long cc: Oleg Nesterov , Matthew Wilcox , Andrew Morton , Pekka Enberg , David Rientjes , Joonsoo Kim , linux-kernel@vger.kernel.org, linux-mm@kvack.org, selinux@vger.kernel.org, Paul Moore , Stephen Smalley , Eric Paris , "Peter Zijlstra (Intel)" Subject: Re: [PATCH 2/4] signal: Make flush_sigqueue() use free_q to release memory In-Reply-To: <93523469-48b0-07c8-54fd-300678af3163@redhat.com> Message-ID: <01000169a6ea5e46-f845b8db-730b-436e-980c-3e4273ad2e34-000000@email.amazonses.com> References: <20190321214512.11524-1-longman@redhat.com> <20190321214512.11524-3-longman@redhat.com> <20190322015208.GD19508@bombadil.infradead.org> <20190322111642.GA28876@redhat.com> <01000169a686689d-bc18fecd-95e1-4b3e-8cd5-dad1b1c570cc-000000@email.amazonses.com> <93523469-48b0-07c8-54fd-300678af3163@redhat.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-SES-Outgoing: 2019.03.22-54.240.9.30 Feedback-ID: 1.us-east-1.fQZZZ0Xtj2+TD7V5apTT/NrT6QKuPgzCT/IC7XYgDKI=:AmazonSES 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 Fri, 22 Mar 2019, Waiman Long wrote: > > > >> I am looking forward to it. > > There is also alrady rcu being used in these paths. kfree_rcu() would not > > be enough? It is an estalished mechanism that is mature and well > > understood. > > > In this case, the memory objects are from kmem caches, so they can't > freed using kfree_rcu(). Oh they can. kfree() can free memory from any slab cache. > There are certainly overhead using the kfree_rcu(), or a > kfree_rcu()-like mechanism. Also I think the actual freeing is done at > SoftIRQ context which can be a problem if there are too many memory > objects to free. No there is none that I am aware of. And this has survived testing of HPC loads with gazillion of objects that have to be freed from multiple processors. We really should not rearchitect this stuff... It took us quite a long time to have this scale well under all loads. Please use rcu_free().