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Date: Wed, 7 Apr 2010 14:09:10 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       Paul Mackerras <paulus@samba.org>
Subject: Re: [PATCH] perf: Store active software events in a hashlist
Message-ID: <20100407120909.GG5143@nowhere>
References: <1270476502-6214-1-git-send-regression-fweisbec@gmail.com> <1270630946.5109.566.camel@twins> <20100407115251.GC5143@nowhere> <1270641405.20295.803.camel@laptop>
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On Wed, Apr 07, 2010 at 01:56:45PM +0200, Peter Zijlstra wrote:
> On Wed, 2010-04-07 at 13:52 +0200, Frederic Weisbecker wrote:
> > On Wed, Apr 07, 2010 at 11:02:26AM +0200, Peter Zijlstra wrote:
> > > On Mon, 2010-04-05 at 16:08 +0200, Frederic Weisbecker wrote:
> > > > +#define SWEVENT_HLIST_BITS     8
> > > > +#define SWEVENT_HLIST_SIZE     ((1 << (SWEVENT_HLIST_BITS + 1)) - 1)
> > > 
> > > That seems to result in 9 bits worth, doesn't it?
> > 
> > 
> > Oh right, I was confused, will zapp the + 1.
> > 
> 
> Also, what you're computing seems to be a mask, not a size
> 
> So with BITS = 8, you want
> SIZE = 1<<BITS = 256
> MASK = SIZE-1 = 255
> 
> right? 


Oh right... damn I suck in maths...