From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752259AbdLBRM5 (ORCPT ); Sat, 2 Dec 2017 12:12:57 -0500 Received: from smtprelay0133.hostedemail.com ([216.40.44.133]:46618 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751905AbdLBRM4 (ORCPT ); Sat, 2 Dec 2017 12:12:56 -0500 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,rostedt@goodmis.org,:::::::::::::,RULES_HIT:41:355:379:541:599:800:960:973:988:989:1260:1277:1311:1313:1314:1345:1359:1437:1515:1516:1518:1534:1539:1593:1594:1711:1730:1747:1777:1792:2393:2553:2559:2562:3138:3139:3140:3141:3142:3352:3622:3865:3866:3867:3868:3871:3872:3874:5007:6261:7875:10004:10400:10848:10967:11026:11232:11473:11658:11914:12740:12760:12895:13069:13311:13357:13439:14181:14659:14721:21080:21627:30054:30070:30090:30091,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:,MSBL:0,DNSBL:none,Custom_rules:0:0:0,LFtime:1,LUA_SUMMARY:none X-HE-Tag: level01_70b0dff25202f X-Filterd-Recvd-Size: 1724 Date: Sat, 2 Dec 2017 12:12:52 -0500 From: Steven Rostedt To: Sebastian Andrzej Siewior Cc: LKML , linux-rt-users , Ingo Molnar , Peter Zijlstra , Daniel Wagner , Thomas Gleixner Subject: Re: [PATCH] sched/rt: Do not do push/pull when there is only one CPU Message-ID: <20171202121252.0bada310@vmware.local.home> In-Reply-To: <20171202125330.xrxspjeedbpr4hk5@linutronix.de> References: <20171201133222.66d41219@gandalf.local.home> <20171202125330.xrxspjeedbpr4hk5@linutronix.de> X-Mailer: Claws Mail 3.15.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2 Dec 2017 13:53:31 +0100 Sebastian Andrzej Siewior wrote: > what about a check next to sched_feat(RT_PUSH_IPI)? I don't know if this > is a hot path or not (due to bitmap_weight). If it is, then I would > suggest something like a jump-label which is enabled if more than one > CPU has been enabled on boot. Yeah I didn't like that because of the overhead. But I was being optimistic that the cpu weight function would be a nit to the actual pull logic. But I have a better plan. I would like to disable RT_PUSH_IPI, but that's a sched feature and that is a constant if we build without sched debugging. v2 coming up. -- Steve