From: Waiman Long Subject: Re: [PATCH v2 2/4] percpu_stats: Enable 64-bit counts in 32-bit architectures Date: Tue, 12 Apr 2016 14:15:22 -0400 Message-ID: <570D3B3A.8080204@hpe.com> 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> <20160411221700.GP24661@htj.duckdns.org> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Cc: Theodore Ts'o , Andreas Dilger , Christoph Lameter , , , Scott J Norton , Douglas Hatch , Toshimitsu Kani To: Tejun Heo Return-path: In-Reply-To: <20160411221700.GP24661@htj.duckdns.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On 04/11/2016 06:17 PM, Tejun Heo wrote: > 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. > I have updated my patch to use percpu_counter instead. Thanks for all the comments and review so far. Cheers, Longman