From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45170) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bJF2p-0006e7-GZ for qemu-devel@nongnu.org; Sat, 02 Jul 2016 03:08:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bJF2k-0006fg-Dx for qemu-devel@nongnu.org; Sat, 02 Jul 2016 03:08:50 -0400 Received: from mail-wm0-x22a.google.com ([2a00:1450:400c:c09::22a]:37923) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bJF2j-0006fX-R0 for qemu-devel@nongnu.org; Sat, 02 Jul 2016 03:08:46 -0400 Received: by mail-wm0-x22a.google.com with SMTP id r201so53734475wme.1 for ; Sat, 02 Jul 2016 00:08:45 -0700 (PDT) References: <1467389770-9738-1-git-send-email-alex.bennee@linaro.org> <20160702005229.GC2295@flamenco> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: <20160702005229.GC2295@flamenco> Date: Sat, 02 Jul 2016 08:08:49 +0100 Message-ID: <87ziq0ikji.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH 0/2] Reduce lock contention on TCG hot-path List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Emilio G. Cota" Cc: mttcg@listserver.greensocs.com, qemu-devel@nongnu.org, fred.konrad@greensocs.com, a.rigo@virtualopensystems.com, serge.fdrv@gmail.com, bobby.prani@gmail.com, rth@twiddle.net, mark.burton@greensocs.com, pbonzini@redhat.com, jan.kiszka@siemens.com, peter.maydell@linaro.org, claudio.fontana@huawei.com Emilio G. Cota writes: > On Fri, Jul 01, 2016 at 17:16:08 +0100, Alex Bennée wrote: > (snip) >> run 1: ret=0 (PASS), time=4.755824 (1/1) >> run 2: ret=0 (PASS), time=4.756076 (2/2) >> run 3: ret=0 (PASS), time=4.755916 (3/3) >> run 4: ret=0 (PASS), time=4.755853 (4/4) >> run 5: ret=0 (PASS), time=4.755929 (5/5) >> Results summary: >> 0: 5 times (100.00%), avg time 4.755920 (0.000000 deviation) > > (snip) >> run 1: ret=0 (PASS), time=9.761559 (1/1) >> run 2: ret=0 (PASS), time=9.511616 (2/2) >> run 3: ret=0 (PASS), time=9.761713 (3/3) >> run 4: ret=0 (PASS), time=10.262504 (4/4) >> run 5: ret=0 (PASS), time=9.762059 (5/5) >> Results summary: >> 0: 5 times (100.00%), avg time 9.811890 (0.060150 deviation) > > This is a needless diversion, but I was explaining this stuff today > to a student so couldn't help but notice. > > The computed deviations seem overly small. For instance, the corrected sample > standard deviation ( https://en.wikipedia.org/wiki/Standard_deviation ) > (which is usually referred to as "standard deviation", or "error") > for the last test should be 0.2742 instead of 0.06. Hmm I was doing from memory but it should be the mean of the sum of the squares of the deviation: # calculate deviation deviation = 0 for r in res: deviation += (r.time - avg_time)**2 deviation = deviation / count > > How are they being computed? I tried to find the source of your script > (in the kvm-unit-tests repo) but couldn't find it. It's a retry script that got a little out of hand: https://github.com/stsquad/retry > > Thanks, > > Emilio -- Alex Bennée