lkml.org 
[lkml]   [2017]   [Nov]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 3/3] perf, tools, script: Allow computing metrics in perf script
On Tue, Nov 21, 2017 at 09:07:14AM -0800, Andi Kleen wrote:
> On Tue, Nov 21, 2017 at 10:28:06AM +0100, Jiri Olsa wrote:
> > On Mon, Nov 20, 2017 at 08:03:06AM -0800, Andi Kleen wrote:
> > > > > Yes it is.
> > > > >
> > > > > It's for the complete sampling period because it is computed
> > > > > over the delta from the last sample to the previous sample.
> > > > >
> > > > > There isn't really a metric at a point, it is always over a interval.
> > > >
> > > > agreed, it's the count we meassured from the last sample.. but the
> > > > 'averaged' word above implies to me we compute some average over the
> > > > 'sampling' period, which we dont do
> > >
> > > Do you have a better word in mind?
> > >
> > > AFAIK average is the right word for this because it's the summary
> > > for that time period.
> >
> > the way I understand it is that we take the values from the current
> > sample and count the metric value.. so the phrase:
> >
> > .. the metric computed is averaged over the whole sampling period,
> > not just for the sample point ...
> >
> > does not make sense to me.. because we take the value of that
> > single 'sample point'.. I dont see any average sum in there
>
> The current samples contains the sum of event counts for a sampling period.
>
> EventA-1 EventA-2 EventA-3 EventA-4
> EventB-1 EventB-2 EventC-3
>
> gap with no events overflow
> |-----------------------------------------------------------------|
> period-start period-end
> ^ ^
> | |
> previous sample current sample
>
>
> So EventA = 4 and EventB = 3 at the sample point
>
> I generate a metric, let's say EventA / EventB. It applies
> to the whole period.
>
> But the metric is over a longer time which does not have the same
> behavior. For example the gap above doesn't have any events, while
> they are clustered at the beginning and end of the sample period.
>
> But we're summing everything together. The metric doesn't know
> that the gap is different than the busy period.
>
> That's what I'm trying to express with averaging.

I see, so averaging to express the sum of the uneven distribution
of the counts.. ook

thanks for bearing with me ;-)
jirka

\
 
 \ /
  Last update: 2017-11-21 22:29    [W:0.041 / U:4.808 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site