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=-2.2 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, URIBL_BLOCKED,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 8DC75C433F5 for ; Fri, 31 Aug 2018 12:07:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3A46120661 for ; Fri, 31 Aug 2018 12:07:48 +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="MlYBTx8z" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3A46120661 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 S1728187AbeHaQO5 (ORCPT ); Fri, 31 Aug 2018 12:14:57 -0400 Received: from merlin.infradead.org ([205.233.59.134]:46940 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726990AbeHaQO4 (ORCPT ); Fri, 31 Aug 2018 12:14:56 -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=yf4vlrsey7BLfPTudc4LWGEbJmcE45qXZ6yi9eiY5po=; b=MlYBTx8z/wYU+N1lf9mPJcQgm xphes2waV1VKb6KGuC4VzWbPd38OO4gXhjoAd/9uGPVDIP1JcuCZaCyHE/KwXZuorDINJV6nxptbV 6opdEIayxilZNC1/g4/0twnB2PCY9f3V+dQxFpMwOxrOHUVFh1w0xa3NjK4GwIO63cMvvkqv9AEZS n0l3BIqxrlXCCjpNVkiKp0xvK4RZBnQ3tDx1FEw2LeaQ9f3X1+25IKssiYu0LB9Y5B4Xfl9ZmsUHD zaqGXLGNIxOkAX+z3+4VOcdJ5rSUxRXcYsGXxbZ7j7c2uZH11OwyAS+8QWC+okfkJvyJGQWQRtokV 8hJx5EpPw==; 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 1fviB2-0006q0-PC; Fri, 31 Aug 2018 12:05:25 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 40C522024D700; Fri, 31 Aug 2018 14:05:22 +0200 (CEST) Date: Fri, 31 Aug 2018 14:05:22 +0200 From: Peter Zijlstra To: Srikar Dronamraju Cc: Ingo Molnar , LKML , Mel Gorman , Rik van Riel , Thomas Gleixner , Michael Ellerman , Heiko Carstens , Suravee Suthikulpanit , linuxppc-dev , Benjamin Herrenschmidt Subject: Re: [PATCH 2/2] sched/topology: Expose numa_mask set/clear functions to arch Message-ID: <20180831120522.GL24124@hirez.programming.kicks-ass.net> References: <20180808081942.GA37418@linux.vnet.ibm.com> <1533920419-17410-1-git-send-email-srikar@linux.vnet.ibm.com> <1533920419-17410-2-git-send-email-srikar@linux.vnet.ibm.com> <20180829080219.GN24124@hirez.programming.kicks-ass.net> <20180831102724.GB8437@linux.vnet.ibm.com> <20180831111253.GJ24124@hirez.programming.kicks-ass.net> <20180831112639.GA24142@hirez.programming.kicks-ass.net> <20180831115350.GC8437@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180831115350.GC8437@linux.vnet.ibm.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 31, 2018 at 04:53:50AM -0700, Srikar Dronamraju wrote: > * Peter Zijlstra [2018-08-31 13:26:39]: > > > On Fri, Aug 31, 2018 at 01:12:53PM +0200, Peter Zijlstra wrote: > > > NAK, not until you've fixed every cpu_to_node() user in the kernel to > > > deal with that mask changing. > > > > Also, what happens if userspace reads that information; uses libnuma and > > then you go and shift the world underneath their feet? > > > > > This is absolutely insane. > > > > The topology events are suppose to be very rare. > From whatever small experiments I have done till now, unless tasks are > bound to both cpu and memory, they seem to be coping well with topology > updates. I know things weren't optimal after a topology change but they > worked. Now after 051f3ca02e46 "Introduce NUMA identity node sched > domain", systems stall. I am only exploring at ways to keep them working > as much as they were before that commit. I'm saying things were fundamentally buggered and this just made it show. If you cannot guarantee cpu:node relations, you do not have NUMA, end of story.