Date: Thu, 18 Mar 2004 19:00:59 +0100
From: Andrea Arcangeli <andrea@suse.de>
To: Robert Love <rml@ximian.com>
Cc: Andrew Morton <akpm@osdl.org>, mjy@geizhals.at,
       linux-kernel@vger.kernel.org
Subject: Re: CONFIG_PREEMPT and server workloads
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References: <40591EC1.1060204@geizhals.at> <20040318060358.GC29530@dualathlon.random> <20040318015004.227fddfb.akpm@osdl.org> <20040318145129.GA2246@dualathlon.random> <1079632130.6043.6.camel@localhost>
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On Thu, Mar 18, 2004 at 12:48:50PM -0500, Robert Love wrote:
> On Thu, 2004-03-18 at 09:51, Andrea Arcangeli wrote:
> 
> > the counter is definitely not optimized away, see:
> 
> This is because of work Dave Miller and Ingo did - irq count, softirq
> count, and lock count (when PREEMPT=y) are unified into preempt_count. 
> 
> So it is intended.
> 
> The unification makes things cleaner and simpler, using one value in
> place of three and one interface and concept in place of many others. 
> It also gives us a single simple thing to check for an overall notion of
> "atomicity", which is what makes debugging so nice.

You're right, I didn't notice the other counters disappeared.  Those
counter existed anyways w/o preempt too, so it would been superflous
with preempt=y to do the accounting in two places. So this is zerocost
with preempt=n and I was wrong claiming superflous preempt leftovers.
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