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[23.128.96.18]) by mx.google.com with ESMTP id do18si11059232ejc.13.2020.09.22.13.33.30; Tue, 22 Sep 2020 13:34:03 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b="ZoRfMp/e"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726655AbgIVUaS (ORCPT + 99 others); Tue, 22 Sep 2020 16:30:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36794 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726567AbgIVUaS (ORCPT ); Tue, 22 Sep 2020 16:30:18 -0400 Received: from mail-ej1-x641.google.com (mail-ej1-x641.google.com [IPv6:2a00:1450:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 89062C0613D0 for ; Tue, 22 Sep 2020 13:30:17 -0700 (PDT) Received: by mail-ej1-x641.google.com with SMTP id nw23so24674792ejb.4 for ; Tue, 22 Sep 2020 13:30:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=QgGt03GMUbG4cqcAoBKuhhh4ICPK+b3ZY93NZCOhnJc=; b=ZoRfMp/eKIXARa2XkW3UpwazOH/ATAFSfzlgmzXWQIw767GhF2po5vLBXfhGLrMo0y b3m5mFnf7nvNb7cBnQ+fISTpGRdCVjQey+TUkT4ZGIDWrkVmXu8sAoSV607TbWlByf2+ 5isz0n9hF3s+Wo+VkkFoldD7suTs/DIMsE/rPboHt06FD9AmZ6gGvz5dy5yIARKRmkNQ X+00i6l4sar2GDS/dnuUCVQrXjV7fyGKCqGL5JtH0yQCtlUA8Ln6KFTXsWSIVBlAa32c wS1yFzgrsAM/Bch572WFtGCYVSppKN4Th0rlXTuHzAzm/aq1gJElN8kUJ4Iq87rzduHq FIcQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=QgGt03GMUbG4cqcAoBKuhhh4ICPK+b3ZY93NZCOhnJc=; b=FkO3kThrneev/MZvbJEhXGuxcV2s2efEPkX3mVfOlOKvheNFvLzJ9G0GAnG49PdBk7 FmYTNKYpjN74Aezx8OjsIZhFQ8OtGpEiVg5OIY1tvP92P8ciTAG/z2UF8YQLgs302pis SBSa/O9j6bG6ZfYXtjSZE9XV2yP00zX5ihiMor8EAiX0vXs5qK8luIe7Gd/F0xfj3BlM zkzjTg+RU6D5MErtzcnqf9ZY1jRR3kmrDwMdfyG+iIUY/LB+qf27PQmYyQcbbrup3Hj7 dJpVYXZXH9hcBxqBwqn+i78ZzeSqANePyBCXUsLw/Toa29Vxtvk8QVO2aPnMf2W/wW0g UtVw== X-Gm-Message-State: AOAM532Kp2a35VENAZ/3VjtokxMyYsDHOsSzLXISQBPaDKx7s9ecEEiT PNwwMVsaqdbz503YqUaoMUCthLije08BgGsXElxLXQ== X-Received: by 2002:a17:906:c045:: with SMTP id bm5mr6614770ejb.311.1600806615934; Tue, 22 Sep 2020 13:30:15 -0700 (PDT) MIME-Version: 1.0 References: <64eca989-f2e7-033f-bb49-084f27c7209b@redhat.com> In-Reply-To: <64eca989-f2e7-033f-bb49-084f27c7209b@redhat.com> From: Wei Wang Date: Tue, 22 Sep 2020 13:30:04 -0700 Message-ID: Subject: Re: [PATCH] sched/rt: Disable RT_RUNTIME_SHARE by default To: Daniel Bristot de Oliveira Cc: LKML , Ingo Molnar , Peter Zijlstra , "J . Avila" , Todd Kjos , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Thomas Gleixner Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 22, 2020 at 12:04 PM Daniel Bristot de Oliveira wrote: > > On 9/22/20 7:14 PM, Wei Wang wrote: > > On Mon, Sep 21, 2020 at 7:40 AM Daniel Bristot de Oliveira > > wrote: > >> > >> The RT_RUNTIME_SHARE sched feature enables the sharing of rt_runtime > >> between CPUs, allowing a CPU to run a real-time task up to 100% of the > >> time while leaving more space for non-real-time tasks to run on the CPU > >> that lend rt_runtime. > >> > >> The problem is that a CPU can easily borrow enough rt_runtime to allow > >> a spinning rt-task to run forever, starving per-cpu tasks like kworkers, > >> which are non-real-time by design. > >> > >> This patch disables RT_RUNTIME_SHARE by default, avoiding this problem. > >> The feature will still be present for users that want to enable it, > >> though. > >> > >> Signed-off-by: Daniel Bristot de Oliveira > >> Cc: Ingo Molnar > >> Cc: Peter Zijlstra > >> Cc: Juri Lelli > >> Cc: Vincent Guittot > >> Cc: Dietmar Eggemann > >> Cc: Steven Rostedt > >> Cc: Ben Segall > >> Cc: Mel Gorman > >> Cc: Daniel Bristot de Oliveira > >> Cc: Thomas Gleixner > >> Cc: linux-kernel@vger.kernel.org > >> --- > >> kernel/sched/features.h | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/kernel/sched/features.h b/kernel/sched/features.h > >> index 7481cd96f391..68d369cba9e4 100644 > >> --- a/kernel/sched/features.h > >> +++ b/kernel/sched/features.h > >> @@ -77,7 +77,7 @@ SCHED_FEAT(WARN_DOUBLE_CLOCK, false) > >> SCHED_FEAT(RT_PUSH_IPI, true) > >> #endif > >> > >> -SCHED_FEAT(RT_RUNTIME_SHARE, true) > >> +SCHED_FEAT(RT_RUNTIME_SHARE, false) > >> SCHED_FEAT(LB_MIN, false) > >> SCHED_FEAT(ATTACH_AGE_LOAD, true) > >> > >> -- > >> 2.26.2 > >> > > > > Tested on an Android device and can no longer see long running RT > > tasks (yes, Android have those for reasons). > > > > So: > > Tested-by: Wei Wang > > ? Yup, thanks for pushing this. > > Thanks! > -- Daniel >