From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id A62DB6B0011 for ; Thu, 28 Apr 2011 10:46:13 -0400 (EDT) Received: by fxm18 with SMTP id 18so2731919fxm.14 for ; Thu, 28 Apr 2011 07:46:12 -0700 (PDT) Date: Thu, 28 Apr 2011 16:44:46 +0200 From: Tejun Heo Subject: Re: [PATCH] percpu: preemptless __per_cpu_counter_add Message-ID: <20110428144446.GC16552@htj.dyndns.org> References: <20110421190807.GK15988@htj.dyndns.org> <1303439580.3981.241.camel@sli10-conroe> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Shaohua Li , Eric Dumazet , "akpm@linux-foundation.org" , "linux-mm@kvack.org" On Thu, Apr 28, 2011 at 09:42:49AM -0500, Christoph Lameter wrote: > > > Can you show in some tests how the chance of deviations is increased? If > > > at all then in some special sitations. Maybe others get better? > > > > It's kinda obvious, isn't it? Do relatively low freq (say, every > > 10ms) +1's and continuously do _sum(). Before, _sum() would never > > deviate much from the real count. After, there will be @batch jumps. > > If you still need proof code, I would write it but please note that > > I'm pretty backed up. > > "Obvious" could mean that you are drawing conclusions without a proper > reasoning chain. Here you assume certain things about the users of the > counters. The same assumptions were made when we had the vm counter > issues. The behavior of counter increments is typically not a regular > stream but occurs in spurts. Eh? Are you saying the above can't happen or the above doesn't matter? -- tejun -- 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