* Peter Zijlstra <[email protected]> wrote:
> On Fri, Nov 15, 2013 at 12:56:29PM +0100, Ingo Molnar wrote:
> > So, here's the current status quo, there's 4 basic types of profiling
> > that 99% of the people are using, in order of popularity:
> >
> > perf record <cmd>
> > perf record -a sleep N
> > perf record -p <PID>
> > perf record -t <TID>
> >
> > The first two (which I'd guess comprise about 95% of real-world usage)
> > have inheritance enabled.
> >
> > The last two (-p/-t) have inheritance disabled by default.
>
> Yes, and I would expect it to be disabled for the TID option as you
> explicitly select a single threads.
Correct.
> For the process wide thing it would make sense to enable inheritance
> by default though.
>
> So the big trade-off is that for single threaded processes which do
> not fork you now have a single buffer, whereas with the inheritance
> option you'll end up with nr_cpus buffers by default.
>
> I suppose for most normal people that's not really an issue; and I
> suppose all people with silly large machines already pay extra
> attention -- but at least make it explicit and very clear that this
> is so.
Do the first variant, 'perf record <cmd>', already use per CPU
buffers?
Thanks,
Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
