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[209.132.183.28]) by mx.google.com with ESMTPS id r25si2434869qvc.91.2019.03.22.11.12.06 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 Mar 2019 11:12:07 -0700 (PDT) Received-SPF: pass (google.com: domain of longman@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of longman@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=longman@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id F30753084024; Fri, 22 Mar 2019 18:12:05 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-47.bos.redhat.com [10.18.17.47]) by smtp.corp.redhat.com (Postfix) with ESMTP id AB6E560142; Fri, 22 Mar 2019 18:12:01 +0000 (UTC) Subject: Re: [PATCH 2/4] signal: Make flush_sigqueue() use free_q to release memory To: Christopher Lameter 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)" 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> From: Waiman Long Openpgp: preference=signencrypt Autocrypt: addr=longman@redhat.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <01000169a686689d-bc18fecd-95e1-4b3e-8cd5-dad1b1c570cc-000000@email.amazonses.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Fri, 22 Mar 2019 18:12:06 +0000 (UTC) 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 03/22/2019 01:50 PM, Christopher Lameter wrote: > 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 n= ot > 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(). 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. I think what Oleg is trying to do is probably the most efficient way. Cheers, Longman