linux-kernel - Re: [PATCH] radeon: use vmalloc instead of kmalloc

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Date:	Tue, 23 Jun 2009 14:23:23 +0200
From:	Jerome Glisse <glisse@...edesktop.org>
To:	Dave Airlie <airlied@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Jerome Glisse <jglisse@...hat.com>, dri-devel@...ts.sf.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] radeon: use vmalloc instead of kmalloc

On Tue, 2009-06-23 at 21:42 +1000, Dave Airlie wrote:
> On Tue, Jun 23, 2009 at 9:35 PM, Peter Zijlstra<peterz@...radead.org> wrote:
> > On Mon, 2009-06-22 at 19:26 +0200, Jerome Glisse wrote:
> >> We don't need to allocated contiguous pages in cs codepath
> >> so use vmalloc instead.
> >
> > Best would be to not require >PAGE_SIZE allocations at all of course.
> 
> It gets messy when you have copy from user and spinlocks, it would be nice
> to just parse the userspace PAGE_SIZE at a time, but it would mean dropping
> a lock we probably need to hold.
> 
> > But barring that, it would be great to have something like:
> >
> >  ptr = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
> >  if (!ptr)
> >    ptr = vmalloc(size);
> 
> we have a drm_calloc_large workaround already for the Intel driver which also
> need this.
> >
> > Also, how long do these allocations live? vmalloc space can be quite
> > limited (i386) and it can fragment too.
> 
> Only an ioctl lifetime so they aren't that bad. We however do have some vmaps
> that might be quite large, mainly the fbcon framebuffer (up to 8MB in
> some cases)
> 
> Dave.


I will rework cs parsing a bit see with what i can come up with. Forget
this patch, i will get back with a new one.

Jerome

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