From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753837AbcDKWRG (ORCPT ); Mon, 11 Apr 2016 18:17:06 -0400 Received: from mail-qg0-f43.google.com ([209.85.192.43]:36245 "EHLO mail-qg0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751427AbcDKWRE (ORCPT ); Mon, 11 Apr 2016 18:17:04 -0400 Date: Mon, 11 Apr 2016 18:17:00 -0400 From: Tejun Heo To: Waiman Long Cc: "Theodore Ts'o" , Andreas Dilger , Christoph Lameter , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, Scott J Norton , Douglas Hatch , Toshimitsu Kani Subject: Re: [PATCH v2 2/4] percpu_stats: Enable 64-bit counts in 32-bit architectures Message-ID: <20160411221700.GP24661@htj.duckdns.org> References: <1460132182-11690-1-git-send-email-Waiman.Long@hpe.com> <1460132182-11690-3-git-send-email-Waiman.Long@hpe.com> <20160408164747.GM24661@htj.duckdns.org> <5707EB44.9020703@hpe.com> <20160408174628.GN24661@htj.duckdns.org> <5707FC52.3070707@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5707FC52.3070707@hpe.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Waiman. On Fri, Apr 08, 2016 at 02:45:38PM -0400, Waiman Long wrote: > The percpu_stats construct allows minimal overhead in maintaining statistics > counts. The percpu_counter construct, on the other hand, has a higher > performance overhead and a bit more complex to set up and tear down when If you're referring to the preemption on/off, as I wrote before, we'll probably be able to improve that with this_cpu_add_return so that the only extra overhead is an easily predictable branch which is extremely cheap. It's better to improve common constructs anyway. > more than one statistics counts are needed. In fact, my first draft of the And yeah, it can be cumbersome to set up and tear down multiple percpu_counters. If there are enough consumers, we can extend percpu_counter to handle multiple counters, right? Thanks. -- tejun