linux-kernel - Re: [PATCH] Export kmap_atomic

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Message-Id: <200809221059.54779.jbarnes@virtuousgeek.org>
Date:	Mon, 22 Sep 2008 10:59:54 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Eric Anholt <eric@...olt.net>, Dave Airlie <airlied@...il.com>,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Export kmap_atomic_pfn for DRM-GEM.

On Wednesday, August 27, 2008 5:22 pm Nick Piggin wrote:
> > However, when other DRM drivers get around to doing memory management,
> > I'm sure they'll also be interested in an ioremap_wc that doesn't eat
> > ipi costs.  For us, the ipis for flushing were eating over 10% of CPU
> > time.  If your patch series cuts that cost, we could drop this piece at
> > that point.
>
> It can cut the cost quite significantly on normal vmap/vunmap loads I
> tested. Whether it will work as well on your workload, I don't know
> but I would have liked to find out. I raised this issue quite a while
> back, so I'm disappointed it had not been tried...

I think Eric has code with the vmap changes now?

Given our discussions at KS/Plumbers would you be ok with acking these 
patches?  Or do you want a repost so you can check out the vmap stuff?

After talking a bit more about it, I think we agreed that the ioctl interface 
is actually a better approach then trying to shoehorn this stuff into system 
calls, so aside from the vmap code (which could be done in 2.6.29 or whenever 
the vmap stuff lands) I think this patchset is pretty close to what we want 
in drm-next now...

Thanks,
Jesse
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