linux-kernel - Re: [PATCH v2] perf, x86: Fix event scheduler for constraints with overlapping counters

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Date:	Fri, 20 May 2011 05:18:55 +0200
From:	Robert Richter <robert.richter@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] perf, x86: Fix event scheduler for constraints with
 overlapping counters

On 19.05.11 14:06:50, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > On Wed, 2011-05-18 at 23:20 +0200, Ingo Molnar wrote:
> > > * Peter Zijlstra <peterz@...radead.org> wrote:
> > > 
> > > > >                         if (c->weight != w)
> > > > >                                 continue;
> > > > >  
> > > > > -                       for_each_set_bit(j, c->idxmsk, X86_PMC_IDX_MAX) {
> > > > > -                               if (!test_bit(j, used_mask))
> > > > > +                       /* for each bit in idxmsk starting from idx */
> > > > > +                       while (idx < X86_PMC_IDX_MAX) {
> > > > > +                               idx = find_next_bit(c->idxmsk, X86_PMC_IDX_MAX,
> > > > > +                                                   idx);
> > > > 
> > > > I'd be mighty tempted to ignore that 80 column rule here ;-)
> > > 
> > > Please put the body of the loop into a helper function, the function is large 
> > > and there are countless col80 uglinesses in it!
> > 
> > I just tried that, its real ugly due to the amount of state you need to
> > pass around.
> 
> Does it help if you put that state into a helper structure?

Yes, this is what I have in mind too. We could iterate on such a state
stucture instead of a couple of single variables. Storing and
restoring the state will then just copying the structure.

-Robert


> 
> Thanks,
> 
> 	Ingo
> 

-- 
Advanced Micro Devices, Inc.
Operating System Research Center

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