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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 B020BC433DF for ; Tue, 16 Jun 2020 07:47:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8FA6B207C4 for ; Tue, 16 Jun 2020 07:47:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726303AbgFPHrE (ORCPT ); Tue, 16 Jun 2020 03:47:04 -0400 Received: from mx2.suse.de ([195.135.220.15]:45026 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725822AbgFPHrD (ORCPT ); Tue, 16 Jun 2020 03:47:03 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 20016AEB1; Tue, 16 Jun 2020 07:47:06 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 410971E1289; Tue, 16 Jun 2020 09:47:01 +0200 (CEST) Date: Tue, 16 Jun 2020 09:47:01 +0200 From: Jan Kara To: Amir Goldstein Cc: Mel Gorman , Jan Kara , Alexander Viro , linux-fsdevel , linux-kernel Subject: Re: [PATCH v2] fs: Do not check if there is a fsnotify watcher on pseudo inodes Message-ID: <20200616074701.GA20086@quack2.suse.cz> References: <20200615121358.GF3183@techsingularity.net> 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-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon 15-06-20 19:26:38, Amir Goldstein wrote: > > This patch changes alloc_file_pseudo() to always opt out of fsnotify by > > setting FMODE_NONOTIFY flag so that no check is made for fsnotify watchers > > on pseudo files. This should be safe as the underlying helper for the > > dentry is d_alloc_pseudo which explicitly states that no lookups are ever > > performed meaning that fanotify should have nothing useful to attach to. > > > > The test motivating this was "perf bench sched messaging --pipe". On > > a single-socket machine using threads the difference of the patch was > > as follows. > > > > 5.7.0 5.7.0 > > vanilla nofsnotify-v1r1 > > Amean 1 1.3837 ( 0.00%) 1.3547 ( 2.10%) > > Amean 3 3.7360 ( 0.00%) 3.6543 ( 2.19%) > > Amean 5 5.8130 ( 0.00%) 5.7233 * 1.54%* > > Amean 7 8.1490 ( 0.00%) 7.9730 * 2.16%* > > Amean 12 14.6843 ( 0.00%) 14.1820 ( 3.42%) > > Amean 18 21.8840 ( 0.00%) 21.7460 ( 0.63%) > > Amean 24 28.8697 ( 0.00%) 29.1680 ( -1.03%) > > Amean 30 36.0787 ( 0.00%) 35.2640 * 2.26%* > > Amean 32 38.0527 ( 0.00%) 38.1223 ( -0.18%) > > > > The difference is small but in some cases it's outside the noise so > > while marginal, there is still some small benefit to ignoring fsnotify > > for files allocated via alloc_file_pseudo in some cases. > > > > Signed-off-by: Mel Gorman > > Reviewed-by: Amir Goldstein Thanks for the patch Mel and for review Amir! I've added the patch to my tree with small amendments to the changelog. Honza -- Jan Kara SUSE Labs, CR