From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751052AbeACRYu convert rfc822-to-8bit (ORCPT + 1 other); Wed, 3 Jan 2018 12:24:50 -0500 Received: from mout.gmx.net ([212.227.17.21]:57878 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750819AbeACRYt (ORCPT ); Wed, 3 Jan 2018 12:24:49 -0500 Message-ID: <1515000270.6513.78.camel@gmx.de> Subject: Re: [patch] sched/fair: Add SIS_MIN_LAT feature to mitigate PELT lag induced stacking From: Mike Galbraith To: LKML Cc: Peter Zijlstra , Ingo Molnar Date: Wed, 03 Jan 2018 18:24:30 +0100 In-Reply-To: <1514803074.8330.8.camel@gmx.de> References: <1514803074.8330.8.camel@gmx.de> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.20.5 Mime-Version: 1.0 Content-Transfer-Encoding: 8BIT X-Provags-ID: V03:K0:rMex8V+qItNkko7y/oGIjXZIyEvp25ZuwNYa6R9PpkXD4u5vaU+ EM9nBt/fQkDrafXqjgzYVN9W+RiWO1wrOPSopCcCbShIKYEyjbr4Ttar8P6aUdI2QbcwWa6 NCvxdWeMueXwK+/CuEi8AAiu2XbODf82vjd4UEji0iQI0xJH96iUYj1k0xrK6eQ5cB4mBLF Z7SyCiOEg79vu5zaCR6Pg== X-UI-Out-Filterresults: notjunk:1;V01:K0:sMNTwRJjuy4=:NIRbryuqgNZSIozsnGqn89 9zJe+lIL6uuYpCV7AO/fd6zP7zh1KrVu2neEuQ4MmHJMK3D0ev2mQtwVH89XXZvJgPKmdMYAI A4Pq1kcmrt0+/FCkY0V6cJs0CjBUvsN23J4jrDa4qyWHRqIP75aloUvPAYf+C0BIYBf97z/KO uEOIZhQS7JNJUaC16eeZt+Jl+KqO/k/YM16Tp5A1P11KHrhd8u1+mWjnnR2eAnLQAZdwn9lvK 6g1VvFgXD7R85JsSmMR5VZUcc/jCI4fNqAfPBBla8mDezdceSH1EEId5+uw+RtdMZLmdAU9M5 zTikGXIeZqYrrS+q5NzDXr41AGTUgnDQIO+40Di3jaC1cLVCN+vzvaeil8244xso34e5OYcYq 1iI7qdQA5Rk+XZkO1gsmb/8UIiO5rkpjmMAp9Z9tC3OjWrt7SRnZeupjRL2HqjhkzLWEv4XZm 818hQFPbBHQqN9TpzqBIdTf1cnkl+pHWL1B/SCORa3aBHBov6ii9Ce7lde9d10KpfBXZWbvqC ZSV0ORll1wEgF1tqrPi8hRb9yMqm8IiLKPowRabDjYd4em8IHOJy9rJJWkC4xQZeqPoTa+Z8w nEDOfdj+2NLfh0kA24RFAhm3RlxKnbbPze2E6M4yP9DBGoEkzHv+xQoDzCI0ru0pdaRwB+Hg1 Nr2WQ8jKvAzTFXl3MU/bbuQpR/QyUQ1VfCLkNdrSClKTBm8rsV/iiDhp2oK1NIcUlM6ixpghO vvgPI8YfyH2BhzIsR4haSB3v22/P+/6SXoPaF6pjcy/hQ/5IsRaTFltMk8psefg5tdXXBIQvL 9qr5LuXeptdjClkkej5DxF1XLik4QIt47xqY0pZECrbEBlc51U= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Mon, 2018-01-01 at 11:37 +0100, Mike Galbraith wrote: > > > Here 0-day bot, here boy.. Forget it 0-day bot, and assorted crickets :) > + /* > + * When heavily loaded, stacking may be the best/only latency option, > + * and LAST_BUDDY the only hope of preventing throughput collapse. > + */ > + if (unlikely(task_cfs_rq(current)->nr_running >= sched_nr_latency) && > + task_cfs_rq(p)->nr_running >= sched_nr_latency) > + return target; With stock knob settings, that's too late to switch from llc -> l2 affinity for sync wakeups, and completely demolished tbench top end on huge socket NUMA box with lots of bandwidth.  Lovely for desktop, somewhere below gawd-awful for big box performance. -Mike