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=-11.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,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 4C432C2D0A3 for ; Thu, 29 Oct 2020 19:05:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E330021548 for ; Thu, 29 Oct 2020 19:05:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Q5y2sd3D" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726214AbgJ2TFI (ORCPT ); Thu, 29 Oct 2020 15:05:08 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:31134 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725778AbgJ2TFH (ORCPT ); Thu, 29 Oct 2020 15:05:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603998305; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=a0p3CSFWKBf8bTXWU5gbr4v+f3iD+GqD+deWi2r7Opo=; b=Q5y2sd3DD/I9iW3St+mCWTpNx6o9/6C3aVbo4hXJFMn+aFKHHhO7hFh7x/MGwn2l1vDt0E oQDvLvevtIMGYN28zahomxXax5jCGikMCP5MUnO/dCYaJ9Iszz06dRxv/tTUVzb0IXjeLT pL4Zrd4eyskZZFl1gQRuSZJjZNAPGBM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-166-ZXpHjZW0NkuUgGUJ31IWBw-1; Thu, 29 Oct 2020 15:05:01 -0400 X-MC-Unique: ZXpHjZW0NkuUgGUJ31IWBw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8EC321009E41; Thu, 29 Oct 2020 19:05:00 +0000 (UTC) Received: from llong.remote.csb (ovpn-116-17.rdu2.redhat.com [10.10.116.17]) by smtp.corp.redhat.com (Postfix) with ESMTP id DA3836EF68; Thu, 29 Oct 2020 19:04:57 +0000 (UTC) Subject: Re: [PATCH v2] inotify: Increase default inotify.max_user_watches limit to 1048576 To: Amir Goldstein Cc: Jan Kara , linux-fsdevel , linux-kernel , Luca BRUNO References: <20201029154535.2074-1-longman@redhat.com> From: Waiman Long Organization: Red Hat Message-ID: <4695fee5-3446-7f5b-ae89-dc48d431a8fe@redhat.com> Date: Thu, 29 Oct 2020 15:04:56 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 10/29/20 2:46 PM, Amir Goldstein wrote: > On Thu, Oct 29, 2020 at 8:05 PM Waiman Long wrote: >> On 10/29/20 1:27 PM, Amir Goldstein wrote: >>> On Thu, Oct 29, 2020 at 5:46 PM 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. It also pins the watched inode as well as an inotify fdinfo >>>> procfs file. >>>> >>>> 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 plus 2 inode have a size close >>>> to 2 kbytes. That means a system with 196GB or more memory should have >>>> the maximum value of 1048576 for inotify.max_user_watches. This default >>>> should be big enough for most use cases. >>>> >>>> With my x86-64 config, the size of xfs_inode, proc_inode and >>>> inotify_inode_mark is 1680 bytes. The estimated INOTIFY_WATCH_COST is >>>> 1760 bytes. >>>> >>>> [v2: increase inotify watch cost as suggested by Amir and Honza] >>>> >>>> Signed-off-by: Waiman Long >>>> --- >>>> fs/notify/inotify/inotify_user.c | 24 +++++++++++++++++++++++- >>>> 1 file changed, 23 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c >>>> index 186722ba3894..37d9f09c226f 100644 >>>> --- a/fs/notify/inotify/inotify_user.c >>>> +++ b/fs/notify/inotify/inotify_user.c >>>> @@ -37,6 +37,16 @@ >>>> >>>> #include >>>> >>>> +/* >>>> + * An inotify watch requires allocating an inotify_inode_mark structure as >>>> + * well as pinning the watched inode and adding inotify fdinfo procfs file. >>> Maybe you misunderstood me. >>> There is no procfs file per watch. >>> There is a procfs file per inotify_init() fd. >>> The fdinfo of that procfile lists all the watches of that inotify instance. >> Thanks for the clarification. Yes, I probably had misunderstood you >> because of the 2 * sizeof(inode) figure you provided. >>>> + * The increase in size of a filesystem inode versus a VFS inode varies >>>> + * depending on the filesystem. An extra 512 bytes is added as rough >>>> + * estimate of the additional filesystem inode cost. >>>> + */ >>>> +#define INOTIFY_WATCH_COST (sizeof(struct inotify_inode_mark) + \ >>>> + 2 * sizeof(struct inode) + 512) >>>> + >>> I would consider going with double the sizeof inode as rough approximation for >>> filesystem inode size. >>> >>> It is a bit less arbitrary than 512 and it has some rationale behind it - >>> Some kernel config options will grow struct inode (debug, smp) >>> The same config options may also grow the filesystem part of the inode. >>> >>> And this approximation can be pretty accurate at times. >>> For example, on Ubuntu 18.04 kernel 5.4.0: >>> inode_cache 608 >>> nfs_inode_cache 1088 >>> btrfs_inode 1168 >>> xfs_inode 1024 >>> ext4_inode_cache 1096 >> Just to clarify, is your original 2 * sizeof(struct inode) figure >> include the filesystem inode overhead or there is an additional inode >> somewhere that I needs to go to 4 * sizeof(struct inode)? > No additional inode. > > #define INOTIFY_WATCH_COST (sizeof(struct inotify_inode_mark) + \ > 2 * sizeof(struct inode)) > > Not sure if the inotify_inode_mark part matters, but it doesn't hurt. > Do note that Jan had a different proposal for fs inode size estimation (1K). > I have no objection to this estimation if Jan insists. > > Thanks, > Amir. > Thanks for the confirmation. 2*sizeof(struct inode) is more than 1k. Besides with debugging turned on, the size will increase more. So that figure is good enough. Cheers, Longman