Re: [patch 0/3] [Announcement] Performance Counters for Linux

David Miller
2008-12-05T07:52:48Z

From: Arjan van de Ven <arjan@infradead.org>
Date: Thu, 4 Dec 2008 23:02:06 -0800

> On Fri, 5 Dec 2008 07:31:31 +0100
> Ingo Molnar <mingo@elte.hu> wrote:
>
> > Btw., i'm curious, why would we want to do that? It skews the results
> > if the task continues executing and counters stop. To get the highest
> > quality profiling output the counters should follow the true state of
> > the task that is profiled - and events should be passed to the
> > monitoring task asynchronously. The _events_ can contain precise
> > coupled information
> > - but the counters should continue.
>
> btw stopping the task on counter overflow is an issue for things that
> want to self profile, like JITs

They can fork off a thread to do this.

No blocking on couter overflow leads to inaccurate results.
This is a pretty fundamental aspect of perf counter usage.