Subject: Re: DRM lock ordering fix series
From: Eric Anholt <eric@anholt.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <andi@firstfloor.org>, linux-kernel@vger.kernel.org,
       dri-devel@lists.sourceforge.net, Nick Piggin <nickpiggin@yahoo.com.au>
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Date: Sun, 29 Mar 2009 23:29:32 -0700
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On Sat, 2009-03-28 at 02:29 +0100, Peter Zijlstra wrote:
> On Sat, 2009-03-28 at 01:58 +0100, Peter Zijlstra wrote:
>=20
> > > OK.  I'm not too excited here -- 10% of 2% of the CPU time doesn't ge=
t
> > > me to the 10% loss that the slow path added up to.  Most of the cost =
is
> > > in k{un,}map_atomic of the returned pages. =20
> >=20
> > Also note that doing large gup() with gup_fast() will be undesirable du=
e
> > to it disabling IRQs. So iterating say several MB worth of pages will
> > hurt like crazy. Currently all gup_fast() users do a single page lookup=
.
>=20
> Also, what's this weird facination with 32bit, can you even buy a 32bit
> only cpu these days?

I work on OpenGL.  Many people using OpenGL want to play commercial
games.  Commercial games are 32-bit.  sysprof doesn't work for 32-on-64,
so I'd lose a critical tool.  Thus, 32-only.

keithp runs 32-on-64, and just about every day we're working together,
we lament that he can't run sysprof on his box.  Getting ~10% of my CPU
back by going 32-on-64 would be nice, but it's not worth not being able
to usefully profile.

--=20
Eric Anholt
eric@anholt.net                         eric.anholt@intel.com


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