From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D69BEC4360C for ; Fri, 4 Oct 2019 13:39:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A63B220700 for ; Fri, 4 Oct 2019 13:39:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A63B220700 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3AE298E0003; Fri, 4 Oct 2019 09:39:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 35EAA8E0006; Fri, 4 Oct 2019 09:39:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 281148E0003; Fri, 4 Oct 2019 09:39:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0051.hostedemail.com [216.40.44.51]) by kanga.kvack.org (Postfix) with ESMTP id 0612E8E0003 for ; Fri, 4 Oct 2019 09:39:31 -0400 (EDT) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 98B3D180AD803 for ; Fri, 4 Oct 2019 13:39:31 +0000 (UTC) X-FDA: 76006209342.23.slip72_3609136c9a037 X-HE-Tag: slip72_3609136c9a037 X-Filterd-Recvd-Size: 2507 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf19.hostedemail.com (Postfix) with ESMTP for ; Fri, 4 Oct 2019 13:39:31 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B6B7BB193; Fri, 4 Oct 2019 13:39:29 +0000 (UTC) Date: Fri, 4 Oct 2019 15:39:29 +0200 From: Michal Hocko To: Konstantin Khlebnikov Cc: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Matthew Wilcox Subject: Re: [PATCH v2] mm/swap: piggyback lru_add_drain_all() calls Message-ID: <20191004133929.GN9578@dhcp22.suse.cz> References: <157019456205.3142.3369423180908482020.stgit@buzz> <20191004131230.GL9578@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) 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 04-10-19 16:32:39, Konstantin Khlebnikov wrote: > On 04/10/2019 16.12, Michal Hocko wrote: > > On Fri 04-10-19 16:09:22, Konstantin Khlebnikov wrote: > > > This is very slow operation. There is no reason to do it again if somebody > > > else already drained all per-cpu vectors while we waited for lock. > > > > > > Piggyback on drain started and finished while we waited for lock: > > > all pages pended at the time of our enter were drained from vectors. > > > > > > Callers like POSIX_FADV_DONTNEED retry their operations once after > > > draining per-cpu vectors when pages have unexpected references. > > > > This describes why we need to wait for preexisted pages on the pvecs but > > the changelog doesn't say anything about improvements this leads to. > > In other words what kind of workloads benefit from it? > > Right now POSIX_FADV_DONTNEED is top user because it have to freeze page > reference when removes it from cache. invalidate_bdev calls it for same reason. > Both are triggered from userspace, so it's easy to generate storm. > > mlock/mlockall no longer calls lru_add_drain_all - I've seen here > serious slowdown on older kernel. > > There are some less obvious paths in memory migration/CMA/offlining > which shouldn't be called frequently. Can you back those claims by any numbers? -- Michal Hocko SUSE Labs