Re: [PATCH 05/33] perf record: Allow the user to disable time stamps
From: Ingo Molnar
Date: Tue Aug 05 2014 - 02:09:08 EST
* Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
>
This patch looks dangerous and misleading to me.
> Time stamps are always implicitely enabled for record currently. The
> old --time/-T option is a nop.
>
> Allow the user to disable timestamps by using --no-time
>
> This can cause some minor misaccounting (by missing mmaps), but
> significantly lowers the size of perf.data
I'm not any big change in size:
-rw------- 1 mingo mingo 384768 Aug 5 08:01 perf.data.timestamps
-rw------- 1 mingo mingo 336952 Aug 5 08:00 perf.data.notimestamps
That's a ~14% reduction - it's certainly noticeable but not
earth-shattering.
And what is called 'minor misaccounting' in the description is
actually a potentially broken profile that people might rely on.
So the patch description misleads twice: by exaggerating the
advantages and also by downplaying the disadvantages.
So either remove the --time option altogether, or fix its
'misaccounting' so that the profile can be relied on.
Thanks,
Ingo
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