Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754036Ab3F0SOi (ORCPT ); Thu, 27 Jun 2013 14:14:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:15593 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753852Ab3F0SOg (ORCPT ); Thu, 27 Jun 2013 14:14:36 -0400 Message-ID: <51CC80E4.8060801@redhat.com> Date: Thu, 27 Jun 2013 20:13:56 +0200 From: Hans de Goede User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130612 Thunderbird/17.0.6 MIME-Version: 1.0 To: Maxime Ripard CC: linux-sunxi@googlegroups.com, John Stultz , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Emilio Lopez , kevin@allwinnertech.com, sunny@allwinnertech.com, shuge@allwinnertech.com Subject: Re: [linux-sunxi] [PATCH 0/8] clocksource: sunxi: Timer fixes and cleanup References: <1372281421-2099-1-git-send-email-maxime.ripard@free-electrons.com> <51CC0566.8010302@redhat.com> <20130627094307.GC8437@lukather> <51CC0BC3.5090309@redhat.com> <20130627165436.GB4319@lukather> In-Reply-To: <20130627165436.GB4319@lukather> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2226 Lines: 69 Hi, On 06/27/2013 06:54 PM, Maxime Ripard wrote: > On Thu, Jun 27, 2013 at 11:54:11AM +0200, Hans de Goede wrote: >> Hi, >> >> On 06/27/2013 11:43 AM, Maxime Ripard wrote: >>> On Thu, Jun 27, 2013 at 11:27:02AM +0200, Hans de Goede wrote: >>>> Hi, >>>> >>>> On 06/26/2013 11:16 PM, Maxime Ripard wrote: >>>>> Hi everyone, >>>>> >>>> >>>> >>>> >>>>> It also finally adds a clocksource from the free running counter found in the >>>>> A10/A13 SoCs. >>>> >>>> Hmm, have you benchmarked this? There have been reports from linux-sunxi kernel >>>> users (xbmc project) that the waiting for the latch is quite slow. Note we >>>> don't have anything better yet in the linux-sunxi kernel. >>> >>> No. I didn't. >>> >>> Do you have any pointers to these discussions? >>> >> >> The original discussion should be somewhere here: >> https://groups.google.com/forum/#!forum/linux-sunxi >> >> But I could not find it (it is probably hidden under >> an unlogical subject). > > I searched a bit and it seems to be that discussion: > https://groups.google.com/d/msg/linux-sunxi/gaTDngPT7Is/oeLtWb1N1wIJ > >> Looking at my own notes (a small TODO file), I've >> written down that the reporter reports: >> >> -current clocksource can cause us to run with interrupts disabled for 17% >> of the time, see "perf top" output >> >> This is with a workload which does a lot of gettimeofday >> calls. > > Siarhei however notes that even higher-end SoCs like the exynos5 have > similar performances with that regard. So I'm not sure we can do > something about it, except what is suggested in the above mail, which > looks rather unsafe. > > Anyway, like you said, we have no easy other solution, and we lacked > such support until now. > > So why not merge this code for now, and try to optimise it later if we > find it's needed. That is fine with me, I just wanted to share that this has shown as a bottleneck in some benchmarks in case anyone has a clever idea to fix it ... Regards, Hans -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/