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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 F1F96C0044C for ; Wed, 31 Oct 2018 19:15:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 979D62081B for ; Wed, 31 Oct 2018 19:15:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="UX9JeRNq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 979D62081B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726316AbeKAEOo (ORCPT ); Thu, 1 Nov 2018 00:14:44 -0400 Received: from merlin.infradead.org ([205.233.59.134]:42840 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725731AbeKAEOo (ORCPT ); Thu, 1 Nov 2018 00:14:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=sLfGGg3UKKR5IgLZJ/dtj6dlYAs1m3mJoJC3Asu1I7c=; b=UX9JeRNqibDQwiMknisbzzY35 vY4oML+3UbkHZfyuAonQS82JPIBQp5UOVwG9cuZsGrf6q/K+/G3uIbHgKxRV3DF7udmsgJ0NNBtX4 ae9Ld2nZfWXjbFHxB1hq3l0xfr+0+UzhMcO/aaKiHtgwV5QTTgmoiZV10RwLrVS18h7WbicC4fgAO Y6N2QZKJQ85hkb80aaZd+9FBFBrFuz1a5QT5jUtM5RB3PZxZWyPC4kiHMf/ih8hNmLEixa6f466gp 99x4yLDkz+EfHAfs/dELwF7Eg6u5plazLof0wc9Y+Ho7HTtRbdwanlwS00UTq0KuW3Yq/5XTgS+n9 ZJDaQaW7g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gHvxF-0006PI-UI; Wed, 31 Oct 2018 19:15:02 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B9E5D20296F15; Wed, 31 Oct 2018 20:14:59 +0100 (CET) Date: Wed, 31 Oct 2018 20:14:59 +0100 From: Peter Zijlstra To: Valentin Schneider Cc: Steven Sistare , mingo@redhat.com, subhra.mazumdar@oracle.com, dhaval.giani@oracle.com, rohit.k.jain@oracle.com, daniel.m.jordan@oracle.com, pavel.tatashin@microsoft.com, matt@codeblueprint.co.uk, umgwanakikbuti@gmail.com, riel@redhat.com, jbacik@fb.com, juri.lelli@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 07/10] sched/fair: Provide can_migrate_task_llc Message-ID: <20181031191459.GA3141@hirez.programming.kicks-ass.net> References: <1540220381-424433-1-git-send-email-steven.sistare@oracle.com> <1540220381-424433-8-git-send-email-steven.sistare@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 29, 2018 at 07:34:50PM +0000, Valentin Schneider wrote: > On a sidenote, I find it a bit odd that the exec_start threshold depends on > sysctl_sched_migration_cost, which to me is more about idle_balance() cost > than "how long does it take for a previously run task to go cache cold". A long long (think 2.6.20 long ago) there was code that did boot-time measurement of the various cache topology costs and that threshold was related to that. That code got killed because of boot to boot variance and dubious benefits. The migration cost is what it was replaced with as a single measure. migration cost was then later abused in the newidle balance because it was over eager. Ideally we'd get rid of it there, because we've now got that much more elaborate accounting, but Rohit tried and found some regression because of that. Maybe we should remove it from newidle anyway.