From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759222Ab3K1OrY (ORCPT ); Thu, 28 Nov 2013 09:47:24 -0500 Received: from merlin.infradead.org ([205.233.59.134]:51425 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754912Ab3K1OrV (ORCPT ); Thu, 28 Nov 2013 09:47:21 -0500 Date: Thu, 28 Nov 2013 15:47:14 +0100 From: Peter Zijlstra To: Tejun Heo Cc: Oleg Nesterov , zhang.yi20@zte.com.cn, lkml , Tetsuo Handa , Ingo Molnar Subject: Re: [PATCH]: exec: avoid propagating PF_NO_SETAFFINITY into userspace child Message-ID: <20131128144714.GV10022@twins.programming.kicks-ass.net> References: <20131127183117.GB13098@mtj.dyndns.org> <20131128091358.GH10022@twins.programming.kicks-ass.net> <20131128114542.GA3826@redhat.com> <20131128121748.GN10022@twins.programming.kicks-ass.net> <20131128133152.GA821@redhat.com> <20131128133947.GR10022@twins.programming.kicks-ass.net> <20131128141329.GB3925@htj.dyndns.org> <20131128143145.GT10022@twins.programming.kicks-ass.net> <20131128143848.GD3925@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131128143848.GD3925@htj.dyndns.org> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 28, 2013 at 09:38:48AM -0500, Tejun Heo wrote: > Hey, Peter. > > On Thu, Nov 28, 2013 at 03:31:45PM +0100, Peter Zijlstra wrote: > > But the WQ_UNBOUND thingies should be just that and should thus not have > > the NO_SETAFFINITY flag set because there is no valid reason to have it > > set. > > > > Regardless of whether the threads are shared between unbound workqueues > > or not. > > Hah? No, we do not want to allow userland to be able to set > affinities on any workqueue workers, period. That's just inviting > people to do weirdest things and then reporting things like "crypt > jobs on some of our 500 machines end up stuck on a single cpu once in > a while" which will eventually be tracked down to some weird shell > script setting affinity on workers doing something else. > > We really want to insulate workers and pool operation from userland. > e.g. unbound workqueues now default to per-NUMA affinity unless > explicitly told not to, which leads to better overall behavior for > most workloads. We do wanna keep those details from userland so that > they can be improved in the future too. Bah, windows mentality of we know better. If they do stupid they get stupid; the only thing we should be concerned about is correctness, they shouldn't be able to crash the system.