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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 9CC71C47404 for ; Fri, 4 Oct 2019 13:39:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 71EC1222C0 for ; Fri, 4 Oct 2019 13:39:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570196372; bh=tS5fRsfiPqn1291pxv549Db3c25yrm1KCjXpxDa5YcQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=RBIA6aCaBtKFhGyaCINoR7T0n6gM6bixiC8l51QGid8FGc1PH+8YGJvqiQt2G+uyS PuL7vHRJBahnN8VBsjBedao2EGNAESe8gh1WO5eYGwP1cVVT6eb2kwSg+kzV7M1pPg t78iplu8s4ARTj4Zx1RNJLNgofoXJRpkDC6i3rhY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388657AbfJDNjb (ORCPT ); Fri, 4 Oct 2019 09:39:31 -0400 Received: from mx2.suse.de ([195.135.220.15]:39234 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388462AbfJDNjb (ORCPT ); Fri, 4 Oct 2019 09:39:31 -0400 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) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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