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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 287C2C388F9 for ; Tue, 27 Oct 2020 16:21:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DB45321556 for ; Tue, 27 Oct 2020 16:21:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1808760AbgJ0QVz (ORCPT ); Tue, 27 Oct 2020 12:21:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:33198 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1804983AbgJ0QAO (ORCPT ); Tue, 27 Oct 2020 12:00:14 -0400 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 83C70ABE3; Tue, 27 Oct 2020 16:00:12 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 331EA1E10F5; Tue, 27 Oct 2020 17:00:12 +0100 (CET) Date: Tue, 27 Oct 2020 17:00:12 +0100 From: Jan Kara To: Waiman Long Cc: Jan Kara , Amir Goldstein , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Luca BRUNO Subject: Re: [PATCH] inotify: Increase default inotify.max_user_watches limit to 1048576 Message-ID: <20201027160012.GE16090@quack2.suse.cz> References: <20201026204418.23197-1-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201026204418.23197-1-longman@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 26-10-20 16:44:18, Waiman Long wrote: > The default value of inotify.max_user_watches sysctl parameter was set > to 8192 since the introduction of the inotify feature in 2005 by > commit 0eeca28300df ("[PATCH] inotify"). Today this value is just too > small for many modern usage. As a result, users have to explicitly set > it to a larger value to make it work. > > After some searching around the web, these are the > inotify.max_user_watches values used by some projects: > - vscode: 524288 > - dropbox support: 100000 > - users on stackexchange: 12228 > - lsyncd user: 2000000 > - code42 support: 1048576 > - monodevelop: 16384 > - tectonic: 524288 > - openshift origin: 65536 > > Each watch point adds an inotify_inode_mark structure to an inode to be > watched. Modeled after the epoll.max_user_watches behavior to adjust the > default value according to the amount of addressable memory available, > make inotify.max_user_watches behave in a similar way to make it use > no more than 1% of addressable memory within the range [8192, 1048576]. > > For 64-bit archs, inotify_inode_mark should have a size of 80 bytes. That > means a system with 8GB or more memory will have the maximum value of > 1048576 for inotify.max_user_watches. This default should be big enough > for most of the use cases. > > Signed-off-by: Waiman Long So I agree that 8192 watches seem to be a bit low today but what you propose seems to be way too much to me. OTOH I agree that having to tune this manually kind of sucks so I'm for auto-tuning of the default. If the computation takes into account the fact that a watch pins an inode as Amir properly notes (that's the main reason why the number of watches is limited), I think limiting to 1% of pinned memory should be bearable. The amount of space pinned by an inode is impossible to estimate exactly (differs for different filesystems) but about 1k for one inode is a sound estimate IMO. Honza > --- > fs/notify/inotify/inotify_user.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c > index 186722ba3894..2da8b7a84b12 100644 > --- a/fs/notify/inotify/inotify_user.c > +++ b/fs/notify/inotify/inotify_user.c > @@ -801,6 +801,18 @@ SYSCALL_DEFINE2(inotify_rm_watch, int, fd, __s32, wd) > */ > static int __init inotify_user_setup(void) > { > + unsigned int watches_max; > + struct sysinfo si; > + > + si_meminfo(&si); > + /* > + * Allow up to 1% of addressible memory to be allocated for inotify > + * watches (per user) limited to the range [8192, 1048576]. > + */ > + watches_max = (((si.totalram - si.totalhigh) / 100) << PAGE_SHIFT) / > + sizeof(struct inotify_inode_mark); > + watches_max = min(1048576U, max(watches_max, 8192U)); > + > BUILD_BUG_ON(IN_ACCESS != FS_ACCESS); > BUILD_BUG_ON(IN_MODIFY != FS_MODIFY); > BUILD_BUG_ON(IN_ATTRIB != FS_ATTRIB); > @@ -827,7 +839,7 @@ static int __init inotify_user_setup(void) > > inotify_max_queued_events = 16384; > init_user_ns.ucount_max[UCOUNT_INOTIFY_INSTANCES] = 128; > - init_user_ns.ucount_max[UCOUNT_INOTIFY_WATCHES] = 8192; > + init_user_ns.ucount_max[UCOUNT_INOTIFY_WATCHES] = watches_max; > > return 0; > } > -- > 2.18.1 > -- Jan Kara SUSE Labs, CR