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From: "Thomas Hellström" <thomas@tungstengraphics.com>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Dave Jones <davej@redhat.com>, Dave Airlie <airlied@linux.ie>,
	Linux Kernel list <linux-kernel@vger.kernel.org>
Subject: Re: [patch 1/2] agpgart - allow user-populated memory types.
Date: Tue, 19 Dec 2006 13:47:29 +0100	[thread overview]
Message-ID: <4587DF61.5020007@tungstengraphics.com> (raw)
In-Reply-To: <1166530649.3365.1237.camel@laptopd505.fenrus.org>

Arjan van de Ven wrote:

>>A short background:
>>The current code uses vmalloc only. The potential use of kmalloc was 
>>introduced
>>to save memory and cpu-speed.
>>All agp drivers expect to see a single memory chunk, so I'm not sure we 
>>want to have an array of pages. That may require rewriting a lot of code.
>>    
>>
>
>but if it's clearly the right thing.....
>How hard can it be? there are what.. 5 or 6 AGP drivers in the kernel?
>
>
>  
>
Hmm,
but we would still waste a lot of memory compared to kmalloc,
when the amount of memory needed is much less than one page, which tends 
to be
a very common case.

Unless we allow the first entry in the array to be the virtual adress to an
arbitrary-sized (max one page) kmalloc() area, the rest of the entries 
can be pointers
to pages allocated with __get_free_page().

This would almost introduce the same level of confusion as the original 
proposal,
and effectively we'd be doing virtual address translation in software 
for each access.

>>If it's acceptable I'd like to go for the vmalloc / kmalloc flag, or at 
>>worst keep the current vmalloc only but that's such a _huge_ memory 
>>waste for small buffers. The flag was the original idea, but 
>>unfortunately the agp_memory struct is part of the drm interface, and I 
>>wasn't sure we could add a variable to it.
>>    
>>
>
>I doubt this is part of the userspace interface so for sure we can
>change it to be right.
>
>
>  
>
/Thomas


  reply	other threads:[~2006-12-19 12:47 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-12-08 18:24 Thomas Hellström
2006-12-08 22:03 ` Arjan van de Ven
2006-12-08 22:17 ` Arjan van de Ven
2006-12-08 23:05   ` Thomas Hellström
2006-12-19  8:47     ` Arjan van de Ven
2006-12-19  9:44       ` Thomas Hellström
2006-12-19 12:17         ` Arjan van de Ven
2006-12-19 12:47           ` Thomas Hellström [this message]
2006-12-19 13:11             ` Arjan van de Ven
2006-12-19 14:11               ` Thomas Hellström
2007-01-08  9:33               ` agpgart: drm-populated " thomas
2007-01-09  2:37                 ` Arjan van de Ven
2007-01-09  8:28                   ` Thomas Hellström
2007-01-09  8:23                 ` [PATCH] agpgart: Allow drm-populated agp " thomas
2007-01-09 14:05                   ` Arjan van de Ven
2007-01-09 14:06                   ` Arjan van de Ven
2007-01-23  9:33                     ` New patch: drm-populated " thomas
2007-01-23  9:33                       ` [PATCH] agpgart: Allow drm-populated agp " thomas

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