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=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 A3BB3C433E9 for ; Thu, 18 Feb 2021 13:01:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 589D964E2F for ; Thu, 18 Feb 2021 13:01:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233074AbhBRM61 (ORCPT ); Thu, 18 Feb 2021 07:58:27 -0500 Received: from mx2.suse.de ([195.135.220.15]:58992 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233038AbhBRLQn (ORCPT ); Thu, 18 Feb 2021 06:16:43 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 8C79FAFCD; Thu, 18 Feb 2021 11:15:58 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 3DE2B1E0F3B; Thu, 18 Feb 2021 12:15:58 +0100 (CET) Date: Thu, 18 Feb 2021 12:15:58 +0100 From: Jan Kara To: Amir Goldstein Cc: Jan Kara , linux-fsdevel Subject: Re: [PATCH 0/7] Performance improvement for fanotify merge Message-ID: <20210218111558.GB16953@quack2.suse.cz> References: <20210202162010.305971-1-amir73il@gmail.com> <20210216160258.GE21108@quack2.suse.cz> <20210217112539.GC14758@quack2.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) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu 18-02-21 12:56:18, Amir Goldstein wrote: > On Wed, Feb 17, 2021 at 1:25 PM Jan Kara wrote: > > > > On Wed 17-02-21 12:52:21, Amir Goldstein wrote: > > > On Tue, Feb 16, 2021 at 6:02 PM Jan Kara wrote: > > > > > > > > Hi Amir! > > > > > > > > Looking at the patches I've got one idea: > > > > > > > > Currently you have fsnotify_event like: > > > > > > > > struct fsnotify_event { > > > > struct list_head list; > > > > unsigned int key; > > > > unsigned int next_bucket; > > > > }; > > > > > > > > And 'list' is used for hashed queue list, next_bucket is used to simulate > > > > single queue out of all the individual lists. The option I'm considering > > > > is: > > > > > > > > struct fsnotify_event { > > > > struct list_head list; > > > > struct fsnotify_event *hash_next; > > > > unsigned int key; > > > > }; > > > > > > > > So 'list' would stay to be used for the single queue of events like it was > > > > before your patches. 'hash_next' would be used for list of events in the > > > > hash chain. The advantage of this scheme would be somewhat more obvious > > > > handling, > > > > > > I can agree to that. > > > > > > > also we can handle removal of permission events (they won't be > > > > hashed so there's no risk of breaking hash-chain in the middle, removal > > > > from global queue is easy as currently). > > > > > > Ok. but I do not really see a value in hashing non-permission events > > > for high priority groups, so this is not a strong argument. > > > > The reason why I thought it is somewhat beneficial is that someone might be > > using higher priority fanotify group just for watching non-permission > > events because so far the group priority makes little difference. And > > conceptually it isn't obvious (from userspace POV) why higher priority > > groups should be merging events less efficiently... > > > > So I implemented your suggestion with ->next_event, but it did not > end up with being able to remove from the middle of the queue. > The thing is we know that permission events are on list #0, but what > we need to find out when removing a permission event is the previous > event in timeline order and we do not have that information. So my idea was that if 'list' is the time ordered list and permission events are *never inserted into the hash* (we don't need them there as hashed lists are used only for merging), then removal of permission events is no problem. > So I stayed with hashed queue only for group priority 0. > > Pushed partly tested result to fanotify_merge branch. > > Will post after testing unless you have reservations. Honza -- Jan Kara SUSE Labs, CR