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From: Andi Kleen <ak@suse.de>
To: Christoph Lameter <clameter@sgi.com>
Subject: Re: Some interesting observations when trying to optimize vmstat handling
Date: Fri, 9 Nov 2007 00:07:42 +0100
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Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
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> There is an interrupt enable overhead of 48 cycles that would be good to
> be able to eliminate (Kernel code usually moves counter increments into
> a neighboring interrupt disable section so that __ function can be used).

Replace the push flags ; popf  with test $IFMASK,flags ; jz 1f; sti ; 1:
That will likely make it much faster (but also bigger) 

The only problem is that there might be some code who relies on 
restore_flags() restoring other flags that IF, but at least for interrupts
and local_irq_save/restore it should be fine to change.

-Andi