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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C39B0C433EF for ; Tue, 26 Oct 2021 10:16:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B0EC660296 for ; Tue, 26 Oct 2021 10:16:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235357AbhJZKTN (ORCPT ); Tue, 26 Oct 2021 06:19:13 -0400 Received: from mout.gmx.net ([212.227.17.22]:50263 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235249AbhJZKSj (ORCPT ); Tue, 26 Oct 2021 06:18:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1635243342; bh=7nOg+WbWudfsXn69esM+imng/AQVqbUy9nVxWfrynf8=; h=X-UI-Sender-Class:Subject:From:To:Cc:Date:In-Reply-To:References; b=LXzsjYkpR7QH6UVC4vGClfdtQHSd8sC3ThirGcT/qGdTQDZz2d10gryPCEQkEhPtM GcphTJCc6t+MIbJ/ITq/a2hgodSMGFODcwc9bqISOm4oaROqw7Mk64JmsxPmTo7NBJ DgCPfHrewp/W5sM46umjyOvY8XEnII6OgMhRoGkc= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from homer.fritz.box ([185.191.218.217]) by mail.gmx.net (mrgmx104 [212.227.17.168]) with ESMTPSA (Nemesis) id 1McYCb-1nFCbY346X-00cwDY; Tue, 26 Oct 2021 12:15:41 +0200 Message-ID: <4105fd08f84c60698b38efcb4d22e999de187d6e.camel@gmx.de> Subject: Re: [PATCH 1/2] sched/fair: Couple wakee flips with heavy wakers From: Mike Galbraith To: Mel Gorman Cc: Peter Zijlstra , Ingo Molnar , Vincent Guittot , Valentin Schneider , Aubrey Li , Barry Song , Srikar Dronamraju , LKML Date: Tue, 26 Oct 2021 12:15:31 +0200 In-Reply-To: <20211026081817.GM3959@techsingularity.net> References: <20211021145603.5313-1-mgorman@techsingularity.net> <20211021145603.5313-2-mgorman@techsingularity.net> <37d8c167df66a1ead16b699115548ca376494c0c.camel@gmx.de> <20211022110534.GJ3959@techsingularity.net> <496d495b290ac69fed75d02ab5915a7871243321.camel@gmx.de> <20211026081817.GM3959@techsingularity.net> 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:c8DccyGYhkrA3FbIEsBnF1sTb32UrEw6yXVgc2GprQXFXpLm7py QNOtrumXwQGYL7W0IMR9xK4NxPqyblxZmgw+c3ltB8EbtWxQjjvC8DIcwLe3movalBc2pHB cMHDLQ02zQYVQnZamPt6xobnX+uHEd7AEhF9peyP2LzuDiJsEXXPDCXWcBFh81QgTRi6Y/Y WhTEilRc9AEi/b0WiUzeg== X-UI-Out-Filterresults: notjunk:1;V03:K0:6dAJDhKzGKA=:gjxR4ys5r0gYZvwoW02U7e nr8KjIlBNf6qyuS1tU8w9xEhhVHUqAswGFb1Qg2fPUOFOO1X/0+X1xKRzGXmQFhIpAsywqVNS +IHs6MPZk5ihUc93znVsxEr87/iVxvvbIElRpoPd+U8+3PBDdcKcr5xGfCiXXS7W0SmiRysZd ftqcvKayuJo3MLNdL3m3aMDaOcwEKiuEu+T/TBctVXLr30UZG8O1Iu/nKu/fllpHJQamtB4OV idi+28bDy9nlC84sD5mcUapIduP7jjnfzlX3GQOeioQ8ovSehrRv1uNEr/BSQXAXqhtHlXUQW HnyPknoCu/7ZwkguxPKuxFAtVgAc/eAUTiiPMHqoc96a2cOXTujgonKmnw8JjRWSDzicNq6Wz d9q9T1f5qPFChTEddqOmhXxu3J1VTypl+uDqN3nQA88/+zdq8yXUwrCQkRBOIOwx47GrhXB4o YOnO9zhg6LfmnmX5Zsy2fSpmvU6G6ybiBEKcFkv4F5mvDzUXuIVSrUM534HdgWadHkUDoRcYF KsxhTQtE3qr90XCva0ZyxweMAHjaGftsgNTeoAD5QI6dgdPAOfkJlA+dLOmBcGmoXEZSgKTq6 KKwhTmAFAS7Sc6w9to4cYR8u3gFZTTxt8byV3E6KX8jdAtkYnSzKOpKhhaCs7NAMB9f5YpzUJ McHZT6l8gYzwcgcPf9dp2M8okaHzp/PMotO7ptdxgcqswiJdrtgHcJ4y0fYQPvS8ya+SirpDJ FW6+NowQpSs52/RiZ1Ae5OPCtmF/jvSSFHhclYik9r3UdoBuXauOJNdmDcHONDsfYPIed05Vz +qN29XqNToyXys+ntNfAUEznsgGQI08VNKT9WCMHyGx1wYaoh7ywCQ1mDf1loRuLcUuQaKe9D crzKtDUE1TnpCkGQi3cGMkcIwyIAZSmfDD9MaI72j59v5a/ljqCMDl4slq370Q/y8TzznlupC D6LUu/fqIeuh8iZkcTZCk5fDFJZDwD81D3v7okk346yIs6mm7jWdKIm1aAyvKPsDCVeh7X5Ev WCqUSHDZfv8D4ExRZEbVVVyRC+kWDGNvLL6NEQBVUiMSXGqlYMBGqF2ocypgCRcR6qKZguXLT PqXHJVemengGOw= Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2021-10-26 at 09:18 +0100, Mel Gorman wrote: > On Mon, Oct 25, 2021 at 08:35:52AM +0200, Mike Galbraith wrote: > > > > > My desktop trace session said distribution improved a bit, but there > > was no meaningful latency or throughput improvement, making for a > > pretty clear "nope" to the above question. > > Another interpretation is that it's simply neutral and does no harm. Yes, patchlet not completely countermanding PELT is a good sign. Had it continuously fired and countermanded PELT entirely, that would mean either that it was busted, or that the desktop load is so damn over- threaded as to be continuously waking more damn threads than can possibly have any benefit whatsoever. Neither of those having happened happening is a good thing. While I really dislike PELT's evil side, it's other face is rather attractive... rob > > It benefiting NUMA box > > hackbench is a valid indicator, but one that is IMO too disconnected > > from the real world to carry much weight. > > > > I think if it's not shown to be harmful to a realistic workload but help= s > an overloaded example then it should be ok. While excessive overload is > rare in a realistic workload, it does happen. There are a few workloads > I've seen bugs for that were triggered when an excessive number of worke= r > threads get spawned and compete for CPU access which in turns leads more > worker threads get spawned. There are application workarounds for this > corner case but it still triggers bugs. >