From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 1A01C6B0022 for ; Thu, 28 Apr 2011 11:05:13 -0400 (EDT) Date: Thu, 28 Apr 2011 10:05:09 -0500 (CDT) From: Christoph Lameter Subject: Re: [PATCH] percpu: preemptless __per_cpu_counter_add In-Reply-To: <20110428145657.GD16552@htj.dyndns.org> Message-ID: References: <20110426121011.GD878@htj.dyndns.org> <1303883009.3981.316.camel@sli10-conroe> <20110427102034.GE31015@htj.dyndns.org> <1303961284.3981.318.camel@sli10-conroe> <20110428100938.GA10721@htj.dyndns.org> <20110428142331.GA16552@htj.dyndns.org> <20110428144446.GC16552@htj.dyndns.org> <20110428145657.GD16552@htj.dyndns.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Shaohua Li , Eric Dumazet , "akpm@linux-foundation.org" , "linux-mm@kvack.org" On Thu, 28 Apr 2011, Tejun Heo wrote: > Hey, > > On Thu, Apr 28, 2011 at 09:52:35AM -0500, Christoph Lameter wrote: > > On Thu, 28 Apr 2011, Tejun Heo wrote: > > > > > Eh? Are you saying the above can't happen or the above doesn't > > > matter? > > > > Its an artificial use case that does not reflect the realities on how > > these counters are typically used. > > Gees, Christoph. That is a test case to show the issue prominently, > which is what a test case is supposed to do. What it means is that > _any_ update can trigger @batch deviation on _sum() regardless of its > frequency or concurrency level and that's the nastiness I've been > talking about over and over again. As far as I understand it: This is a test case where you want to show us the atomic_t type behavior of _sum. This only works in such an artificial test case. In reality batches of updates will modify any 'accurate' result that you may have obtained from the _sum function. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org