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=-0.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 B5683C433F5 for ; Thu, 23 Sep 2021 13:14:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9411861211 for ; Thu, 23 Sep 2021 13:14:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241204AbhIWNQR (ORCPT ); Thu, 23 Sep 2021 09:16:17 -0400 Received: from mout.gmx.net ([212.227.15.18]:37265 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234515AbhIWNQP (ORCPT ); Thu, 23 Sep 2021 09:16:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmx.net; s=badeba3b8450; t=1632402854; bh=lU0u6JPJIXL4HNlA8zPgv8plXcK4dBpVGakj8NOVom8=; h=X-UI-Sender-Class:Subject:From:To:Cc:Date:In-Reply-To:References; b=TBfVgL8052DicUYWMqujuaLTV6qdTSWCEht7c7enLKL5RdhhcZWYgvs+TfOGUqTnr 9NAlkd+7huEfRW6hyvi/2D43nImDTmZ3s9Cyen1Xyje2ggcffc/uRl0m558vRzB1oh P7vqgYQxJmAWi+in8Ry6Xyawi2NotnPR+Pz2olLY= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from homer.fritz.box ([185.221.149.175]) by mail.gmx.net (mrgmx005 [212.227.17.190]) with ESMTPSA (Nemesis) id 1N0FxV-1mpAOn2ujX-00xG6j; Thu, 23 Sep 2021 15:14:14 +0200 Message-ID: <38b22e307f1c912e9fb22155b04d4d0064b9e63d.camel@gmx.de> Subject: Re: [PATCH 2/2] sched/fair: Scale wakeup granularity relative to nr_running From: Mike Galbraith To: Vincent Guittot Cc: Mel Gorman , Peter Zijlstra , Ingo Molnar , Valentin Schneider , Aubrey Li , Barry Song , Srikar Dronamraju , LKML Date: Thu, 23 Sep 2021 15:14:12 +0200 In-Reply-To: References: <20210920142614.4891-1-mgorman@techsingularity.net> <20210920142614.4891-3-mgorman@techsingularity.net> <22e7133d674b82853a5ee64d3f5fc6b35a8e18d6.camel@gmx.de> <20210921103621.GM3959@techsingularity.net> <20210922132002.GX3959@techsingularity.net> <20210922150457.GA3959@techsingularity.net> <20210922173853.GB3959@techsingularity.net> <50400427070018eff83b0782d2e26c0cc9ff4521.camel@gmx.de> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:OHvRlOVkMqRD9dJFokSxGNbtMxypgfw9JtZ8qjIhQCTAHb/QWxb QXN+MFlPkUZ308fgj9Xyz6hKfGHCUuv5fv8tCacKZjff1RRnuvosbfug/uiHiDyv+lyp1ou A7ImuWrtLUehImGtndDM+OpGUC82pBw1UGwfGuRqkedXAFLDOMDWt8Xx4eN07S/0sVtOXoS SWLpedF41xNopVDshu/MA== X-UI-Out-Filterresults: notjunk:1;V03:K0:iLXJGYKnwVA=:192kKRCfxQ+8DtfaTNzpzm fCMA6J+vysiGYE5faKBqQjYvZdKe+NVNzLE+JbsOdk86ts+lXMkU0G/Jr2el+Er1AH7cPZGtL djHvOi2cDB4+r9eshk1Ni68ql4LvJFvApVkuJfan4+4JrHIqUwBzTDqVkQFcqkqVpRn70IhC/ zP3j7T5A3tplzfpUowplfG3h6YAXLb/id9Axkt2+q+wIGCdNCLBSWdwqG3BhoyAzdFWpBnRuB /HV8DjzhBks4a2ZxoIwcNZDZ1HwbR+HIejsc12iDCJx/2WNQjTMOU90+G0LmNR6i3LcIsfHvj yGp5jHRa9i7siA1WBFBUbOnGnkNTKtPgTTWRANWRIe2J6GzINJTzBvJb0jmETjO4UuCjeew/i X8YRLxsi/SDCP88d5LB7ddi/kkm5o0+DgAqFILu0/k9iOY1N3XJ1rC0sMotOSMY5avbDmpp6w NJYf94wWeaOl2uwzTq2oX2gX0aTs/YhiBfDU1sdE5BD1Q9t/m7n6Nn8OSL2qxWFLxvduABgJd FdQ6JXDvuJeRhqC8c21A+FM3JVaeviHqoZHmzalHB8ZBRjfpI2zuoRlAo5h06Bui4FpLgXrUv EkcW9UqE3EjFc2DluJNQOX59s+h5CjdZTEbngBx2UavMs6Usl20HbbtVHov7KuRAKhe+asJ1M XWxH/qEVGO6+oi/lu6uSdvB1QdjwAknMeKzMrW7qekrea58Dw5kLS1nozziHIuXAL780qJ/37 MpS2kxVZP6zY3Pl3YLe7YXPk07DFCslePyeRYvXsaP28eSGThQfNlok0Cfb252BPLmPO+avhP b7v9rEMucKB8TEbiL67CwXS+FYa1Yn3p6kubOIDSNTm02tw6Ns2tKfXTNuugHQ9z/MgvYD579 DswFj05X3WpwkK55V+4GyyP5LzsS5dx/UGe7LZIt3obVYVjE9XUI2jGdycXQjQ0rHnCmJdmwy p8l2JhX+lY5rxYLAt6nhIAVlsV2YAR1Nz3Tdse5Cy+EOMmWDSld+84wXuHKpDf398X9Q03MCk 9F8pwRBORfrKdpU6eDRZsY7fOLc9fHLwQfMd0j/JTAzDlatDxBusDbZESgjmmavzYYyopIB2S MsHqqBmz7Zgj9E= Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2021-09-23 at 14:41 +0200, Vincent Guittot wrote: > On Thu, 23 Sept 2021 at 11:22, Mike Galbraith wrote: > > > > On Thu, 2021-09-23 at 10:40 +0200, Vincent Guittot wrote: > > > > > > a 100us value should even be enough to fix Mel's problem without > > > impacting common wakeup preemption cases. > > > > It'd be nice if it turn out to be something that simple, but color me > > skeptical.=C2=A0 I've tried various preemption throttling schemes, and= while > > Let's see what the results will show. I tend to agree that this will > not be enough to cover all use cases and I don't see any other way to > cover all cases than getting some inputs from the threads about their > latency fairness which bring us back to some kind of latency niceness > value What dooms the dirt simple solution is: tasks that dip lightly but frequently are a thing ;-) Take nfs threads, tell 'em frequent preemption ain't cool, and no matter how you diplomatically you say it, they react in the only way they can, by sucking at their job. -Mike