Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757587Ab2HPPcr (ORCPT ); Thu, 16 Aug 2012 11:32:47 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:47869 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752688Ab2HPPcp (ORCPT ); Thu, 16 Aug 2012 11:32:45 -0400 MIME-Version: 1.0 In-Reply-To: <1345128138.29668.42.camel@twins> References: <1345124749.31092.2.camel@localhost.localdomain> <1345125384.29668.30.camel@twins> <1345128138.29668.42.camel@twins> Date: Thu, 16 Aug 2012 21:32:45 +0600 Message-ID: Subject: Re: Add rq->nr_uninterruptible count to dest cpu's rq while CPU goes down. From: Rakib Mullick To: Peter Zijlstra Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, paulmck Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1598 Lines: 42 On 8/16/12, Peter Zijlstra wrote: > On Thu, 2012-08-16 at 20:28 +0600, Rakib Mullick wrote: > >> nr_uninterruptible is coupled with tasks on the runqueue to calculate >> nr_active numbers. > > It is not.. nr_uninterruptible is incremented on the cpu the task goes > to sleep and decremented on the cpu doing the wakeup. > If nr_uninterruptible's life cycle is this simple then, while CPU goes down, nr_uninterruptible count will be decremented when all the tasks are moved to other CPUs and should be fine. > This means that nr_uninterruptible is a complete mess and any per-cpu > value isn't meaningful at all. > Well, if nr_uninterruptible is a mess, then this patch has no meaning. And also I think migrate_nr_uninterruptible() is meaning less too. > It is quite possible to always have the inc on cpu0 and the decrement on > cpu1, yielding results like: > > {1000, -1000} for an effective nr_uninterruptible = 0. Taking either cpu > down will then migrate whatever delta it has to another cpu, but there > might only be a single task, yet the delta is +-1000. > >> In calc_load_fold_active(), this nr_active numbers are used to >> calculate delta. This is how I understand this part and seeing some >> impact. > > You understand wrong, please re-read the comment added in commit > 5167e8d5. > Yes, reading. Thanks, Rakib. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/