From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx167.postini.com [74.125.245.167]) by kanga.kvack.org (Postfix) with SMTP id 4ECBB6B003B for ; Thu, 6 Jun 2013 00:02:34 -0400 (EDT) Date: Thu, 6 Jun 2013 14:02:29 +1000 From: Dave Chinner Subject: Re: [PATCH v10 03/35] dcache: convert dentry_stat.nr_unused to per-cpu counters Message-ID: <20130606040229.GW29338@dastard> References: <1370287804-3481-1-git-send-email-glommer@openvz.org> <1370287804-3481-4-git-send-email-glommer@openvz.org> <20130605160731.91a5cd3ff700367f5e155d83@linux-foundation.org> <20130606014509.GN29338@dastard> <20130605194801.f9b25abf.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130605194801.f9b25abf.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Glauber Costa , linux-fsdevel@vger.kernel.org, Mel Gorman , linux-mm@kvack.org, cgroups@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com, Michal Hocko , Johannes Weiner , hughd@google.com, Greg Thelen , Dave Chinner On Wed, Jun 05, 2013 at 07:48:01PM -0700, Andrew Morton wrote: > On Thu, 6 Jun 2013 11:45:09 +1000 Dave Chinner wrote: > > > Andrew, if you want to push the changes back to generic per-cpu > > counters through to Linus, then I'll write the patches for you. But > > - and this is a big but - I'll only do this if you are going to deal > > with the "performance trumps all other concerns" fanatics over > > whether it should be merged or not. I have better things to do > > with my time have a flamewar over trivial details like this. > > Please view my comments as a critique of the changelog, not of the code. > > There are presumably good (but undisclosed) reasons for going this way, > but this question is so bleeding obvious that the decision should have > been addressed up-front and in good detail. The answer is so bleeding obvious I didn't think it needed to be documented. ;) i.e. implement it the same way that it's sibling is implemented because consistency is good.... > And, preferably, with benchmark numbers. Because it might have been > the wrong decision - stranger things have happened. I've never been able to measure the difference in fast-path performance that can be attributed to the generic CPU counters having more overhead than the special ones. If you've got any workload where the fast-path counter overhead shows up in a profile, I'd be very interested.... Cheers, dave. -- Dave Chinner david@fromorbit.com -- 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