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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 71CB6C43461 for ; Mon, 14 Sep 2020 09:33:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1DBF320719 for ; Mon, 14 Sep 2020 09:33:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726392AbgINJdh (ORCPT ); Mon, 14 Sep 2020 05:33:37 -0400 Received: from mx2.suse.de ([195.135.220.15]:38474 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726351AbgINJdJ (ORCPT ); Mon, 14 Sep 2020 05:33:09 -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 AC4B1AE85; Mon, 14 Sep 2020 09:33:19 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id BC1581E12EF; Mon, 14 Sep 2020 11:33:03 +0200 (CEST) Date: Mon, 14 Sep 2020 11:33:03 +0200 From: Jan Kara To: =?iso-8859-1?Q?Rog=E9rio?= Brito Cc: Linus Torvalds , Amir Goldstein , Hugh Dickins , Michael Larabel , Ted Ts'o , Andreas Dilger , Ext4 Developers List , Jan Kara , linux-fsdevel Subject: Re: Kernel Benchmarking Message-ID: <20200914093303.GA7347@quack2.suse.cz> References: <8bb582d2-2841-94eb-8862-91d1225d5ebc@MichaelLarabel.com> <0cbc959e-1b8d-8d7e-1dc6-672cf5b3899a@MichaelLarabel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit 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 Sat 12-09-20 17:32:41, Rogério Brito wrote: > Now, to the subject: is this that you describe (RCU or VFS), in some sense, > related to, say, copying a "big" file (e.g., a movie) to a "slow" media (in > my case, a USB thumb drive, so that I can watch said movie on my TV)? > > I've seen backtraces mentioning "task xxx hung for yyy seconds" and a > non-reponsive cp process at that... I say RCU or VFS because I see this > with the thumb drives with vfat filesystems (so, it wouldn't be quite > related to ext4, apart from the fact that all my Linux-specific > filesystems are ext4). This is very likely completely different problem. I'd need to see exact messages and kernel traces but usually errors like these happen when the IO is very slow and other things (such as grabbing some locks or doing memory allocation) get blocked waiting for that IO. In the case Linus speaks about this is really more about CPU bound tasks that heavily hammer the same cached contents. Honza -- Jan Kara SUSE Labs, CR