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Wed, 13 Oct 2021 17:38:38 +0000 Date: Wed, 13 Oct 2021 13:38:34 -0400 From: Daniel Jordan To: Michal Hocko Cc: David Hildenbrand , ultrachin@163.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, brookxu.cn@gmail.com, chen xiaoguang , zeng jingxiang , lu yihui , Claudio Imbrenda Subject: Re: [PATCH] mm: Free per cpu pages async to shorten program exit time Message-ID: <20211013173834.lrff6wloae4c6uol@oracle.com> References: <20211008063933.331989-1-ultrachin@163.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: BL1PR13CA0398.namprd13.prod.outlook.com (2603:10b6:208:2c2::13) To BYAPR10MB2966.namprd10.prod.outlook.com (2603:10b6:a03:8c::27) MIME-Version: 1.0 Received: from oracle.com (98.229.125.203) by BL1PR13CA0398.namprd13.prod.outlook.com (2603:10b6:208:2c2::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4608.4 via Frontend Transport; Wed, 13 Oct 2021 17:38:37 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: ad6ccf34-30e3-4fdb-b511-08d98e704a47 X-MS-TrafficTypeDiagnostic: BYAPR10MB3381: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; 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dkim=pass header.d=oracle.com header.s=corp-2021-07-09 header.b=QMS577bR; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b="MHBrvht/"; spf=none (imf27.hostedemail.com: domain of daniel.m.jordan@oracle.com has no SPF policy when checking 205.220.165.32) smtp.mailfrom=daniel.m.jordan@oracle.com; dmarc=pass (policy=none) header.from=oracle.com X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C577C70000A7 X-Stat-Signature: 6midj3obunaxzg4wo15g6o5a3w68cjkd X-HE-Tag: 1634146737-426537 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: (I'm just back from vacation) On Mon, Oct 11, 2021 at 11:28:10AM +0200, Michal Hocko wrote: > On Fri 08-10-21 10:17:50, David Hildenbrand wrote: > > On 08.10.21 08:39, ultrachin@163.com wrote: > > > From: chen xiaoguang > > > > > > The exit time is long when program allocated big memory and > > > the most time consuming part is free memory which takes 99.9% > > > of the total exit time. By using async free we can save 25% of > > > exit time. > > > > > > Signed-off-by: chen xiaoguang > > > Signed-off-by: zeng jingxiang > > > Signed-off-by: lu yihui > > > > I recently discussed with Claudio if it would be possible to tear down the > > process MM deferred, because for some use cases (secure/encrypted > > virtualization, very large mmaps) tearing down the page tables is already > > the much more expensive operation. > > > > There is mmdrop_async(), and I wondered if one could reuse that concept when > > tearing down a process -- I didn't look into feasibility, however, so it's > > just some very rough idea. > > This is not a new problem. Large process tear down can take ages. The > primary road block has been accounting. This lot of work has to be > accounted to the proper domain (e.g. cpu cgroup). A deferred and > properly accounted context implementation is still lacking AFAIK. Right, still doesn't exist. It's coming though, and there was a session on it at LPC this year[1]. > I have a vague recollection we have padata framework but I am not sure > anybody has explored this to be used for the address space shutdown. > IIRC Daniel Jordan was active in that area. Yeah, address space teardown is one of the things we want to use padata for. It's on the list. [1] https://linuxplumbersconf.org/event/11/contributions/1041/