From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qa0-f42.google.com (mail-qa0-f42.google.com [209.85.216.42]) by kanga.kvack.org (Postfix) with ESMTP id 9C76D6B0035 for ; Fri, 9 May 2014 11:28:32 -0400 (EDT) Received: by mail-qa0-f42.google.com with SMTP id j5so4266794qaq.29 for ; Fri, 09 May 2014 08:28:32 -0700 (PDT) Received: from qmta08.emeryville.ca.mail.comcast.net (qmta08.emeryville.ca.mail.comcast.net. [2001:558:fe2d:43:76:96:30:80]) by mx.google.com with ESMTP id u7si2202330qab.6.2014.05.09.08.28.31 for ; Fri, 09 May 2014 08:28:32 -0700 (PDT) Date: Fri, 9 May 2014 10:28:27 -0500 (CDT) From: Christoph Lameter Subject: Re: vmstat: On demand vmstat workers V4 In-Reply-To: Message-ID: References: <20140508142903.c2ef166c95d2b8acd0d7ea7d@linux-foundation.org> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner Cc: Andrew Morton , Gilad Ben-Yossef , Tejun Heo , John Stultz , Mike Frysinger , Minchan Kim , Hakan Akkan , Max Krasnyansky , Frederic Weisbecker , "Paul E. McKenney" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, hughd@google.com, viresh.kumar@linaro.org On Fri, 9 May 2014, Thomas Gleixner wrote: > > Ok how do I figure out that cpu? I'd rather have a specific cpu that > > never changes. > > I followed the full nohz development only losely, but back then when > all started here at my place with frederic, we had a way to define the > housekeeper cpu. I think we lazily had it hardwired to 0 :) Yes that would be the easiest and simplest. We dedicate cpu 0 to OS services around here anyways. > That probably changed, but I'm sure there is still a way to define a > housekeeper. And we should simply force the timekeeping on that > housekeeper. That comes with the price, that the housekeeper is not > allowed to go deep idle, but I bet that in HPC scenarios this does not > matter at all simply because the whole machine is under full load. Excellent. Yes. Good. > > > > The vmstat kworker thread checks every 2 seconds if there are vmstat > > updates that need to be folded into the global statistics. This is not > > necessary if the application is running and no OS services are being used. > > Thus we could switch off vmstat updates and avoid taking the processor > > away from the application. > > > > This has also been noted by multiple other people at was brought up at the > > mm summit by others who noted the same issues. > > I understand why you want to get this done by a housekeeper, I just > did not understand why we need this whole move it around business is > required. This came about because of another objection against having it simply fixed to a processor. After all that processor may be disabled etc etc. -- 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/ . Don't email: email@kvack.org