From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754624AbYFJRlk (ORCPT ); Tue, 10 Jun 2008 13:41:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752572AbYFJRld (ORCPT ); Tue, 10 Jun 2008 13:41:33 -0400 Received: from e2.ny.us.ibm.com ([32.97.182.142]:50076 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750737AbYFJRlc (ORCPT ); Tue, 10 Jun 2008 13:41:32 -0400 Subject: Re: [RFC PATCH 5/5] refresh VM committed space after a task migration From: Dave Hansen To: Andrea Righi Cc: balbir@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, kosaki.motohiro@jp.fujitsu.com, containers@lists.osdl.org, menage@google.com, xemul@openvz.org In-Reply-To: <1213054383-18137-6-git-send-email-righi.andrea@gmail.com> References: <> <1213054383-18137-6-git-send-email-righi.andrea@gmail.com> Content-Type: text/plain Date: Tue, 10 Jun 2008 10:41:28 -0700 Message-Id: <1213119688.13882.13.camel@nimitz> Mime-Version: 1.0 X-Mailer: Evolution 2.22.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2008-06-10 at 01:33 +0200, Andrea Righi wrote: > + preempt_disable(); > + committed = atomic_long_read(&p->vm_committed_space); > + atomic_long_sub(committed, &old_mem->vmacct.vm_committed_space); > + atomic_long_add(committed, &mem->vmacct.vm_committed_space); > + preempt_enable(); > out: > mmput(mm); > } Why bother with the preempt stuff here? What does the actually protect against? I assume that you're trying to keep other tasks that might run on this CPU from seeing weird, inconsistent numbers in here. Is there some other looks that keeps *other* cpus from seeing this? In any case, I think it needs a big, fat comment. -- Dave