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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A7DD4C433FE for ; Wed, 5 Oct 2022 15:46:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230090AbiJEPq5 (ORCPT ); Wed, 5 Oct 2022 11:46:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40742 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229588AbiJEPqx (ORCPT ); Wed, 5 Oct 2022 11:46:53 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1B58878BE3 for ; Wed, 5 Oct 2022 08:46:52 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9D066113E; Wed, 5 Oct 2022 08:46:58 -0700 (PDT) Received: from wubuntu (unknown [10.57.32.122]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 752CD3F67D; Wed, 5 Oct 2022 08:46:49 -0700 (PDT) Date: Wed, 5 Oct 2022 16:46:47 +0100 From: Qais Yousef To: David Laight Cc: 'John Stultz' , LKML , Connor O'Brien , John Dias , Rick Yiu , John Kacur , Chris Redpath , Abhijeet Dharmapurikar , Peter Zijlstra , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Thomas Gleixner , "kernel-team@android.com" , "J . Avila" Subject: Re: [RFC PATCH v3 2/3] sched: Avoid placing RT threads on cores handling long softirqs Message-ID: <20221005154647.vok6unu3vnzxp74d@wubuntu> References: <20220921012550.3288570-1-jstultz@google.com> <20220921012550.3288570-3-jstultz@google.com> <20220928125517.ei64pxfucaem55cr@wubuntu> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/04/22 09:50, David Laight wrote: [...] > > That's fair. Digging through the patch history in the Android trees, > > the first pass was for all softirqs but then restricted to remove > > known short-running ones. > > From the bug history and what I can directly reproduce, the net and > > block softirqs have definitely caused trouble, but I don't see a > > specific example from TASKLET, so I'm ok dropping that for now, and > > should we get specific evidence we can argue for it in a future patch. > > > > So I'll drop TASKLET from the list here. Thanks for the suggestion! > > I've also seen the code that finally frees memory freed under rcu > take a long time. > That was a workload sending a lot of UDP/RTP from a raw socket using > IP_HDRINC - each send allocated a structure (fib?) that was freed from > the rcu (timer?) softint callback. I'm assuming this is a network driver that using RCU callback to free some memory? > > But, actually, one of the biggest causes of RT wakeup latency > was a normal thread looping without a cond_resched() call. > In my case some graphics driver doing page flushes of the > display memory. Were these drivers that cause these problem in-tree or out-of-tree? Thanks -- Qais Yousef