From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751788AbeBBM65 (ORCPT ); Fri, 2 Feb 2018 07:58:57 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:55463 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751416AbeBBM6u (ORCPT ); Fri, 2 Feb 2018 07:58:50 -0500 Date: Fri, 2 Feb 2018 13:58:46 +0100 From: Peter Zijlstra To: "Rafael J. Wysocki" Cc: Mel Gorman , Mike Galbraith , Matt Fleming , LKML , srinivas.pandruvada@linux.intel.com Subject: Re: [PATCH 4/4] sched/fair: Use a recently used CPU as an idle candidate and the basis for SIS Message-ID: <20180202125846.GM2269@hirez.programming.kicks-ass.net> References: <20180130104555.4125-1-mgorman@techsingularity.net> <3838689.GpfBVtfPr0@aspire.rjw.lan> <20180201091104.GW2269@hirez.programming.kicks-ass.net> <8930678.7E2iWGoJnn@aspire.rjw.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8930678.7E2iWGoJnn@aspire.rjw.lan> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 02, 2018 at 12:42:29PM +0100, Rafael J. Wysocki wrote: > > Yes, too many synchronous IPIs, which themselves are typically already > > more expensive than the MSR access. > > We could do all of the updates in one IPI (as Srinivas said), but it would be > more code, and custom code for that matter. > > Is this really worth it for a slow path like this one? Probably not, still, the pattern really annoys me ;-)