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Re: [PATCH] MIPS: Make collection of FPU emulator statistics optional.

To: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Subject: Re: [PATCH] MIPS: Make collection of FPU emulator statistics optional.
From: Ralf Baechle <ralf@linux-mips.org>
Date: Tue, 3 Nov 2009 10:37:43 +0100
Cc: David Daney <ddaney@caviumnetworks.com>, linux-mips@linux-mips.org
In-reply-to: <20091103093024.GA6425@alpha.franken.de>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1257207155-14517-1-git-send-email-ddaney@caviumnetworks.com> <20091103093024.GA6425@alpha.franken.de>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.19 (2009-01-05)
On Tue, Nov 03, 2009 at 10:30:24AM +0100, Thomas Bogendoerfer wrote:

> On Mon, Nov 02, 2009 at 04:12:35PM -0800, David Daney wrote:
> > On SMP systems, the collection of statistics can cause cache line
> > bouncing in the lines associated with the counters.  Make the
> > statistics configurable so this can be avoided.  Also we need to make
> > the counters atomic_t so that they can be reliably modified on SMP
> > systems.
> 
> how about making it a per_cpu thing and avoid the atomic instructions ?

Working on that.  The tricky part is that statistics may end up somewhat
inaccurate when a reader iterates over the per-CPU array of stats to add
them all up.  I've not found a solution for that yet but then again it
should not be something which actually would cause pain.

  Ralf

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