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=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 B7F83C55189 for ; Wed, 22 Apr 2020 11:56:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9BDF521655 for ; Wed, 22 Apr 2020 11:56:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727930AbgDVL4T (ORCPT ); Wed, 22 Apr 2020 07:56:19 -0400 Received: from foss.arm.com ([217.140.110.172]:48256 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726948AbgDVL4T (ORCPT ); Wed, 22 Apr 2020 07:56:19 -0400 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 7B3F931B; Wed, 22 Apr 2020 04:56:18 -0700 (PDT) Received: from e113632-lin (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CE7D33F6CF; Wed, 22 Apr 2020 04:56:16 -0700 (PDT) References: <20200422112719.826676174@infradead.org> <20200422112831.574539982@infradead.org> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Peter Zijlstra Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, rostedt@goodmis.org, qais.yousef@arm.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, daniel.lezcano@linaro.org, sudeep.holla@arm.com Subject: Re: [PATCH 06/23] sched,psci: Convert to sched_set_fifo*() In-reply-to: <20200422112831.574539982@infradead.org> Date: Wed, 22 Apr 2020 12:55:53 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/04/20 12:27, Peter Zijlstra wrote: > Because SCHED_FIFO is a broken scheduler model (see previous patches) > take away the priority field, the kernel can't possibly make an > informed decision. > > Effectively changes prio from 99 to 50. > > XXX this thing is horrific, it basically open-codes a stop-machine and > idle. > I went and tried to clean up the thing. I didn't find a clean way to use stop_machine() + play_idle() (stoppers can't sleep), but I did manage to get something usable with the existing FIFO threads, play_idle_precise() and the cpuidle state usage stats, so the whole homebrewed idle thing can go. I also just tested it with 50 prio and big surprise it didn't change anything (it ends up being sibling of idle injection). So FWIW: Acked-by: Valentin Schneider > Cc: daniel.lezcano@linaro.org > Cc: sudeep.holla@arm.com > Signed-off-by: Peter Zijlstra (Intel) > Reviewed-by: Ingo Molnar