linux-kernel - Re: [PATCH 5/7] perf, tools, stat: Implement --metric-only mode

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Date:	Thu, 10 Mar 2016 12:28:35 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	acme@...nel.org, jolsa@...nel.org, linux-kernel@...r.kernel.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 5/7] perf, tools, stat: Implement --metric-only mode

On Thu, Mar 03, 2016 at 03:57:36PM -0800, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> Add a new mode to only print metrics. Sometimes we don't care about
> the raw values, just want the computed metrics. This allows more
> compact printing, so with -I each sample is only a single line.
> This also allows easier plotting and processing with other tools.
> 
> The main target is with using --topdown, but it also works with
> -T and standard perf stat. A few metrics are not supported.
> 
> To avoiding having to hardcode all the metrics in the code it uses
> a two pass approach: first compute dummy metrics and only
> print the headers in the print_metric callback. Then use the callback
> to print the actual values.
> 
> There are some additional changes
> in the stat printout code to handle all metrics being on a single line.
> 
> One issue is that the column code doesn't know in advance what events
> are not supported by the CPU, and it would be hard to find out
> as this could change based on dynamic conditions. That causes
> empty columns in some cases.
> 
> The output can be fairly wide, often you may need more than 80 columns.
> 
> Example:
> 
> % perf stat -a -I 1000 --metric-only
>      1.001452803 frontend cycles idle insn per cycle       stalled cycles per insn branch-misses of all branches
>      1.001452803  158.91%               0.66                2.39                    2.92%
>      2.002192321  180.63%               0.76                2.08                    2.96%
>      3.003088282  150.59%               0.62                2.57                    2.84%
>      4.004369835  196.20%               0.98                1.62                    3.79%
>      5.005227314  231.98%               0.84                1.90                    4.71%

could you please also make a change to display some kind of warning
if there're no events to produce any metrics?

[jolsa@...va perf]$ sudo ./perf stat -a -I 1000 --metric-only -e cycles
     1.000172990 
     1.000172990 
     2.000448614 

this could be follow up patch

Acked-by: Jiri Olsa <jolsa@...nel.org>


thanks,
jirka