linux-kernel - Re: [patch 0/2] reduce agpgart memory allocation time

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Message-Id: <1217834079.9799.1.camel@sli10-desk.sh.intel.com>
Date:	Mon, 04 Aug 2008 15:14:39 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Dave Airlie <airlied@...il.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [patch 0/2] reduce agpgart memory allocation time

On Mon, 2008-08-04 at 16:53 +1000, Dave Airlie wrote:
> On Mon, Aug 4, 2008 at 4:51 PM, Shaohua Li <shaohua.li@...el.com> wrote:
> > agpgart memory allocation is quite expensive. For each page agpgart
> > allocated, it changes the page to uc and as result flush tlb/cache for
> > the page. In my test, Intel Xorg driver takes about 0.2s for a 32M 3D
> > fb, and the total time for memory allocation is about 0.33s when intel
> > xorg driver initializes. Below patches fix the gap. It can reduce the
> > time to 0.03s, so xserver can boot 0.3s faster.
> >
> 
> This approach is quite like what was there before, and I think was
> objected to on the grounds the caller might forget to
> call the flush and leave the system in an inconsistent state.
> Personally I've never bought that argument, its not like we have
> thousands of users for this API.
> 
> I proposed an alternative interface but I failed to get it merged and
> ran out of time
> http://www.ussg.iu.edu/hypermail/linux/kernel/0804.3/1112.html
> 
> I was trying to get the cpa interface to allow arrays of pages to be
> passed in, I was then going to change AGP like
> http://git.kernel.org/?p=linux/kernel/git/airlied/agp-2.6.git;a=shortlog;h=agp-pageattr2
This is good too.

> I really should fix those patches up at some point, feel free to base
> a system on those if someone objects to the method with the call site
> doing the flush.
Ok, if people object the method, I'll refresh your patches.

Thanks,
Shaohua

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