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 7412DEE49A3 for ; Tue, 22 Aug 2023 06:10:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232933AbjHVGKQ (ORCPT ); Tue, 22 Aug 2023 02:10:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50652 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231494AbjHVGKM (ORCPT ); Tue, 22 Aug 2023 02:10:12 -0400 Received: from mout.gmx.net (mout.gmx.net [212.227.15.18]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5AD2D186; Mon, 21 Aug 2023 23:10:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.de; s=s31663417; t=1692684590; x=1693289390; i=efault@gmx.de; bh=2tIsDYryRj0UAmEjOltYAR/Nh7ihW0NC/V1nBUGx1kA=; h=X-UI-Sender-Class:Subject:From:To:Cc:Date:In-Reply-To:References; b=GKP2KNZilrQJTwqLjWq3/paltMm5ZhLQjimFRkXpVQo/T2r7VKhMikWOhO7nG0xSttW8Qh+ kBLWf/z+8zzrPneUCuM3UVd+UTQXC0PmQ9ZGlZrbRVp9EWYrDG6ZPva7SPFRkUwK7nNu5L/H3 bPqOEa5IdjF8pKtb6esXe81fa6TUzswSSkrqLQXNgjshpWcYLJKTfRIhb+AwhBXM2Zf2Kp909 2O/Z09+UfSaXXXUJ9SFNY6tHhHy41/hEEL4fgFX0+2IiXK/b2GN2V/Wnc76OXmBtOsGOgbYYc LalE86t3zm+XQc7m9erMCJnxDDNpcB6TU5OTwewh9Ym0kqrtLWnA== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from homer.fritz.box ([185.191.218.235]) by mail.gmx.net (mrgmx004 [212.227.17.190]) with ESMTPSA (Nemesis) id 1MRTRH-1qKDz12F4n-00NQ79; Tue, 22 Aug 2023 08:09:50 +0200 Message-ID: <0e153dd25900af70f91e4a73f960320e6daf3c6a.camel@gmx.de> Subject: Re: [tip: sched/core] sched/eevdf: Curb wakeup-preemption From: Mike Galbraith To: K Prateek Nayak , "Peter Zijlstra (Intel)" Cc: linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org, x86@kernel.org, Chen Yu , Gautham Shenoy Date: Tue, 22 Aug 2023 08:09:49 +0200 In-Reply-To: References: <20230816134059.GC982867@hirez.programming.kicks-ass.net> <169228500414.27769.13366308319134164264.tip-bot2@tip-bot2> <21f3d376-17d6-8fb6-5f35-507ea931c0d3@amd.com> <02f6a15f094adb3c8d9957b031941d6bd10c2e43.camel@gmx.de> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.4 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:u3CnOMDnjSy84k/tEVdsCc4+nf0vvYBCRSP6abII0NWoUDEHpx9 BMHqp/tXG160g8qS+lPbdOrf4gEnXOd+Mo+xpJQBlCHDPV7/eLS5MPnjguOXbyVsavdbsos k+MPT2PGip20X8tc6aZLA/DiIm9VwDaQHPZGrLgBD3KmMjRkR5NiLoBBbCMCPTdbvKY4PWd 4zSVJKciWvXqjUuFx8VFw== UI-OutboundReport: notjunk:1;M01:P0:mOKMarcG88Y=;iHZioWDAFWTc7bGQQ2B79P4B0HA nXH7jRLD7+UnTe0M2FVZELkzHppqJrT/HOUw8V0Y7FvhxgOaOrjWbFN9o7XqCLChNeG9q4IpN OaKiKugh5cyERGP+Yh9suxX1Epp1KlNYaNs/Iq5ZjYdvRyPO2DZFZxoTWPnx3FpXI4UGEXbWx 3brbrQPZcSGKgv+/z+HTAxNQej74kYxovHmbs9PghEEwM7HezxuE36DxZBz5GI+pgHgTvJB6Y xLESEBLbWuZq0GWqU7jUZmrPmtJ9E2puJJt5PzAbdsp8L8aRS4HY9eCtwOm41S1zs7u3re+vQ Jox0Wi3eAj2O84dd7rini6/v3eFF6IrOoddBd6f8uKFfBBg2/PmKUPq0/IAUXB//YsrgAJ7jW 93OuUYpHn741wmdhq/phz4HEinQ90k71jIcqXPCTT4DzArh6gmN5uc5LQ9EjJFlrEQ/5z7AZ3 FXP/bjmc5uVaJC9mIyR/wBmIubZmMU4yN3YfyJJCUvoCgYEtn8MQXwRP7ouK78QUoOTJMshOF txTqxLRbEPPT4hIDWzV1sWxzfTJVEazqEQU6N2dpY9Vl8CtrSg+7NaxkjOO3vgAJm83zIcXAh +Yvu/xp42FJ1LDLQSoCWk224/b1YHFINQ+1ZAv+5zuDCI+CVVjqoNJn0gIdXvPz98o0W/JQOu O9xyxMmzXLZCS/f1zrn8rRkqgUnwfQYiVXxIB0JrlrhNuXgrDNt+LdjVfNLCI8J2afsOLwTOT PlwRYTmrUMO+zGkO8E3xUEawnTSAd46KxQ4VymxXFMrqe0YwRM2UKqztRuf/UxENN8BwU1P8i jiM/JK2FFOMklPQvzEmIFvTdEe5J1K2o2uRzeYi3ntM4Gl35VSm8bwDaeloyUJvctq8Hw/zSf eY4TqCmRYrv0qfeCd+Uq4846fqCLsYXP0daqYT6l4hEaLUflRoh/1iu9owzdilhds+Bnw4JiW 2s4qV4NryTzPeSRelZNWk6IttxE= Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2023-08-22 at 08:33 +0530, K Prateek Nayak wrote: > Hello Mike, Greetings! > > FWIW, there are more tbench shards lying behind EEVDF than in front. > > > > tbench 8 on old i7-4790 box > > 4.4.302=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 4024 > > 6.4.11=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 3668 > > 6.4.11-eevdf 3522 > > > > I agree, but on servers, tbench has been useful to identify a variety of > issues [1][2][3] and I believe it is better to pick some shards up than > leave them lying around for others to step on :) Absolutely, but in this case it isn't due to various overheads wiggling about and/or bitrot, everything's identical except the scheduler, and its overhead essentially is too. taskset -c 3 pipe-test 6.4.11 1.420033 usecs/loop -- avg 1.420033 1408.4 KHz 6.4.11-eevdf 1.413024 usecs/loop -- avg 1.413024 1415.4 KHz Methinks these shards are due to tbench simply being one of those things that happens to like the CFS notion of short term fairness a bit better than the EEVDF notion, ie are inevitable fallout tied to the very thing that makes EEVDF service less spiky that CFS, and thus will be difficult to sweep up. Too bad I didn't save Peter's test hack to make EEVDF use the same notion of fair (not a keeper) as I think that would likely prove it. -Mike