linux-kernel - Re: [PATCH 4/4] perf, x86: Fix event scheduler to solve complex scheduling problems

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Message-ID: <1302948940.32491.12.camel@twins>
Date:	Sat, 16 Apr 2011 12:15:40 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Robert Richter <robert.richter@....com>,
	Stephane Eranian <eranian@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 4/4] perf, x86: Fix event scheduler to solve complex
 scheduling problems

On Sat, 2011-04-16 at 12:14 +0200, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > On Sat, 2011-04-16 at 11:43 +0200, Ingo Molnar wrote:
> > > I'd also prefer if we first had actual testcases in 'perf test' for all these 
> > > failures - it took an *awfully* long time to find these regressions (the event 
> > > scheduler code has been committed for months), while with proper testcases it 
> > > would only take a second to run 'perf test'. 
> > 
> > These cases only exist on AMD F15, I don't think there's many people
> > with such systems around.
> 
> Well, if the trend continues we'll have more twisted constraints and more bugs 
> of this sort, so having a testsuite sure cannot hurt, right?

For sure. But the problem with writing test cases at the perf userspace
level is that they're very hardware specific. It would be much easier to
write unit tests for the solver itself.
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