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Date: Mon, 27 Apr 2009 13:27:22 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: balbir@linux.vnet.ibm.com
Cc: kosaki.motohiro@jp.fujitsu.com, dave@linux.vnet.ibm.com,
       linux-mm@kvack.org, linux-kernel@vger.kernel.org, ebmunson@us.ibm.com,
       mel@linux.vnet.ibm.com, cl@linux-foundation.org
Subject: Re: meminfo Committed_AS underflows
Message-Id: <20090427132722.926b07f1.akpm@linux-foundation.org>
In-Reply-To: <20090415084713.GU7082@balbir.in.ibm.com>
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On Wed, 15 Apr 2009 14:17:13 +0530
Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

> * KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> [2009-04-15 13:10:06]:
> 
> > > * KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> [2009-04-15 11:04:59]:
> > > 
> > > >  	committed = atomic_long_read(&vm_committed_space);
> > > > +	if (committed < 0)
> > > > +		committed = 0;
> > > 

Is there a reason why we can't use a boring old percpu_counter for
vm_committed_space?  That way the meminfo code can just use
percpu_counter_read_positive().

Or perhaps just percpu_counter_read().  The percpu_counter code does a
better job of handling large cpu counts than the
mysteriously-duplicative open-coded stuff we have there.