linux-kernel - Re: [patch 2/2] reduce tlb/cache flush times of agpgart memory allocation

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Date:	Sun, 17 Aug 2008 20:56:43 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	"Li, Shaohua" <shaohua.li@...el.com>
Cc:	Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>,
	"airlied@...ux.ie" <airlied@...ux.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [patch 2/2] reduce tlb/cache flush times of agpgart memory
 allocation

On Mon, 18 Aug 2008 09:21:12 +0800
"Li, Shaohua" <shaohua.li@...el.com> wrote:

> 
> >
> >it really needs something else instead; it needs airlied's array
> >allocator
> >otherwise you hit the second wall as well (the pat checks per page)
> Somebody should have a measurement. In my test, the real bottleneck
> is the cache flush. It appears flush cache page is slow if there are
> a lot of pages, In my patch, I use a wbinvd. This can be optimized to
> do wbinvd with a threshold. Maybe airlied can change his patch with
> this way.


it would be great if you had time to update his patch and this to
it...

and the logic probably should be "if there's more than X pags in the
the array, just use wbinvd".
Although wbinvd is very painful if you have 12Mb of cache and you wipe
it for all cores in the system ;-(



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