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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D1BAC433EF for ; Sat, 6 Nov 2021 11:30:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A95D36124F for ; Sat, 6 Nov 2021 11:30:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org A95D36124F Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=rere.qmqm.pl Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id C57AA94000B; Sat, 6 Nov 2021 07:30:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C07FB94000A; Sat, 6 Nov 2021 07:30:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AF5A394000B; Sat, 6 Nov 2021 07:30:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0148.hostedemail.com [216.40.44.148]) by kanga.kvack.org (Postfix) with ESMTP id A18AD94000A for ; Sat, 6 Nov 2021 07:30:01 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 582598249980 for ; Sat, 6 Nov 2021 11:30:01 +0000 (UTC) X-FDA: 78778286202.08.B3F604F Received: from rere.qmqm.pl (rere.qmqm.pl [91.227.64.183]) by imf21.hostedemail.com (Postfix) with ESMTP id 9EF38D036A5F for ; Sat, 6 Nov 2021 11:29:55 +0000 (UTC) Received: from remote.user (localhost [127.0.0.1]) by rere.qmqm.pl (Postfix) with ESMTPSA id 4HmZss2pjdz8K; Sat, 6 Nov 2021 12:29:53 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=rere.qmqm.pl; s=1; t=1636198197; bh=WAutzEgYEkmalNSwQrpbordkhKZLQ/Y22509TsCal1M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=MoSDr5iITx3E3YPjbwkyIUAMMz2VmRaGqyp931kZX9YG+QyaLES6TvE+QwQNSCXlJ fpc5I73Jklg2OzmXxu2LMdsy9vNLA7EBPNnzQtR/b7pam2rbJ41auAZmoiKWDoGoTh 33ZJgvXhhdDgMv5Gftq0VWNj2quwtGMnCQ05Vicp9WOB1XHJmcwdB4C6fV5moIbunY 2pHxjtQgDkyQmIbCl5sYp6e9aq2kjDEzW8DTwxKTUYFbt5WG7t6QG/dNh1ogsZV3La pN/Cdf+ZUSXgzppa++BQRGky7Z/Oiq8oAuUHz4R2kaNp0awXgwxWySm/P9++rhyRyL YNV8/t5iEpSKQ== X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.3 at mail Date: Sat, 6 Nov 2021 12:29:51 +0100 From: =?iso-8859-2?Q?Micha=B3_Miros=B3aw?= To: Yafang Shao Cc: Andrew Morton , Kees Cook , Steven Rostedt , Mathieu Desnoyers , Arnaldo Carvalho de Melo , Petr Mladek , Peter Zijlstra , Al Viro , Valentin Schneider , Qiang Zhang , robdclark , christian , Dietmar Eggemann , Ingo Molnar , Juri Lelli , Vincent Guittot , David Miller , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin Lau , Song Liu , Yonghong Song , john fastabend , KP Singh , dennis.dalessandro@cornelisnetworks.com, mike.marciniszyn@cornelisnetworks.com, dledford@redhat.com, jgg@ziepe.ca, linux-rdma@vger.kernel.org, netdev , bpf , "linux-perf-use." , linux-fsdevel@vger.kernel.org, Linux MM , LKML , kernel test robot , kbuild test robot Subject: Re: [PATCH v7 00/11] extend task comm from 16 to 24 Message-ID: References: <20211101060419.4682-1-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-2 Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 9EF38D036A5F X-Stat-Signature: 8txhu5x81i6ei95jbx5c3nn9zty5fj7m Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=rere.qmqm.pl header.s=1 header.b=MoSDr5iI; spf=pass (imf21.hostedemail.com: domain of mirq-linux@rere.qmqm.pl designates 91.227.64.183 as permitted sender) smtp.mailfrom=mirq-linux@rere.qmqm.pl; dmarc=pass (policy=reject) header.from=rere.qmqm.pl X-HE-Tag: 1636198195-376462 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sat, Nov 06, 2021 at 05:12:24PM +0800, Yafang Shao wrote: > On Sat, Nov 6, 2021 at 7:57 AM Micha=B3 Miros=B3aw wrote: > > > > On Fri, Nov 05, 2021 at 02:34:58PM +0800, Yafang Shao wrote: > > > On Thu, Nov 4, 2021 at 9:37 AM Micha=B3 Miros=B3aw wrote: > > > > > > > > On Mon, Nov 01, 2021 at 06:04:08AM +0000, Yafang Shao wrote: > > > > > There're many truncated kthreads in the kernel, which may make = trouble > > > > > for the user, for example, the user can't get detailed device > > > > > information from the task comm. > > > > > > > > > > This patchset tries to improve this problem fundamentally by ex= tending > > > > > the task comm size from 16 to 24, which is a very simple way. > > > > [...] > > > > > > > > Hi, > > > > > > > > I've tried something like this a few years back. My attempt got m= ostly > > > > lost in the mailing lists, but I'm still carrying the patches in = my > > > > tree [1]. My target was userspace thread names, and it turned out= more > > > > involved than I had time for. > > > > > > > > [1] https://rere.qmqm.pl/git/?p=3Dlinux;a=3Dcommit;h=3D2c3814268c= af2b1fee6d1a0b61fd1730ce135d4a > > > > and its parents > > > > > > > > > > Hi Michal, > > > > > > Thanks for the information. > > > > > > I have looked through your patches. It seems to contain six patche= s > > > now and can be divided into three parts per my understanding. > > > > > > 1. extend task comm len > > > This parts contains below 4 patches: > > > [prctl: prepare for bigger > > > TASK_COMM_LEN](https://rere.qmqm.pl/git/?p=3Dlinux;a=3Dcommit;h=3Dc= fd99db9cf911bb4d106889aeba1dfe89b6527d0) > > > [bluetooth: prepare for bigger > > > TASK_COMM_LEN](https://rere.qmqm.pl/git/?p=3Dlinux;a=3Dcommit;h=3Db= a2805f5196865b81cc6fc938ea53af2c7c2c892) > > > [taskstats: prepare for bigger > > > TASK_COMM_LEN](https://rere.qmqm.pl/git/?p=3Dlinux;a=3Dcommit;h=3D4= d29bfedc57b36607915a0171f4864ec504908ca) > > > [mm: make TASK_COMM_LEN > > > configurable](https://rere.qmqm.pl/git/?p=3Dlinux;a=3Dcommit;h=3D36= 2acc35582445174589184c738c4d86ec7d174b) > > > > > > What kind of userspace issues makes you extend the task comm length= ? > > > Why not just use /proc/[pid]/cmdline ? > > > > This was to enable longer thread names (as set by pthread_setname_np(= )). > > Currently its 16 bytes, and that's too short for e.g. Chrome's or Fir= efox'es > > threads. I believe that FreeBSD has 32-byte limit and so I expect tha= t > > major portable code is already prepared for bigger thread names. > > >=20 > The comm len in FreeBSD is (19 + 1) bytes[1], but that is still larger > than Linux :) > The task comm is short for many applications, that is why cmdline is > introduced per my understanding, but pthread_{set, get}name_np() is > reading/writing the comm or via prctl(2) rather than reading/writing > the cmdline... >=20 > Is the truncated Chrome or Firefox thread comm really harmful or is > extending the task comm just for portable? > Could you pls show me some examples if the short comm is really harmful= ? >=20 > Per my understanding, if the short comm is harmful to applications > then it is worth extending it. > But if it is only for portable code, it may not be worth extending it. >=20 > [1]. https://github.com/freebsd/freebsd-src/blob/main/sys/sys/param.h#L= 126 I don't think it is harmful as in exposing a bug or something. It's just inconvenient when debugging a system where you can't differentiate between threads because their names have been cut too short. Best Regards Micha=B3=A0Miros=B3aw