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Message-ID: <20140731235825.GH28673@intel.com>
Date: Fri, 1 Aug 2014 07:58:25 +0800
From: Yuyang Du <yuyang.du@...el.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Aaron Lu <aaron.lu@...el.com>, Rik van Riel <riel@...hat.com>,
LKML <linux-kernel@...r.kernel.org>, lkp@...org,
jhladky@...hat.com, Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [LKP] [sched/numa] a43455a1d57: +94.1%
proc-vmstat.numa_hint_faults_local
On Fri, Aug 01, 2014 at 09:29:11AM +0200, Peter Zijlstra wrote:
> On Fri, Aug 01, 2014 at 10:03:30AM +0800, Aaron Lu wrote:
> > > > > ebe06187bf2aec1 a43455a1d572daf7b730fe12e
> > > > > --------------- -------------------------
> > > > > 94500 ~ 3% +115.6% 203711 ~ 6% ivb42/hackbench/50%-threads-pipe
> > > > > 67745 ~ 4% +64.1% 111174 ~ 5% lkp-snb01/hackbench/50%-threads-socket
> > > > > 162245 ~ 3% +94.1% 314885 ~ 6% TOTAL proc-vmstat.numa_hint_faults_local
>
> > It means, for commit ebe06187bf2aec1, the number for
> > num_hint_local_faults is 94500 for ivb42 machine and 67745 for lkp-snb01
> > machine. The 3%, 4% following that number means the deviation of the
> > different runs to their average(we usually run it multiple times to
> > phase out possible sharp values). We should probably remove that
> > percentage, as they cause confusion if no detailed explanation and may
> > not mean much to the commit author and others(if the deviation is big
> > enough, we should simply drop that result).
>
> Nah, variance is good, but the typical symbol would be +- or the fancy
> ±.
>
> ~ when used as a unary op means 'approx' or 'about' or 'same order'
> ~ when used as a binary op means equivalence, a weaker equal, often in
> the vein of the unary op meaning.
>
> Also see: http://en.wikipedia.org/wiki/Tilde#Mathematics
>
> So while I think having a measure of variance is good, I think you
> picked entirely the wrong symbol.
Or, maybe you can use σ (lower case sigma) to indicate stddev, :)
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