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From: Andi Kleen <andi@firstfloor.org>
To: Cliff Wickman <public-cpw-sJ/iWh9BUns@plane.gmane.org>
Cc: public-linux-kernel-u79uwXL29TY76Z2rM5mHXA@plane.gmane.org,
	public-kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@plane.gmane.org,
	public-mingo-X9Un+BFzKDI@plane.gmane.org
Subject: Re: [PATCH] x86: copy_oldmem_page using cached addressing
Date: Wed, 08 Sep 2010 21:42:18 +0200	[thread overview]
Message-ID: <87eid4vx7p.fsf@basil.nowhere.org> (raw)
In-Reply-To: <E1OtMLz-0001yp-Ia@eag09.americas.sgi.com> (Cliff Wickman's message of "Wed, 08 Sep 2010 10:14:27 -0500")



Cliff Wickman <cpw-sJ/iWh9BUns@public.gmane.org> writes:

> From: Cliff Wickman <cpw-sJ/iWh9BUns@public.gmane.org>
>
> The copy of /proc/vmcore to a user buffer proceeds much faster
> if the kernel addresses memory as cached.
>
> With this patch we have seen an increase in transfer rate from less than
> 15MB/s to 80-460MB/s, depending on size of the transfer.  This makes
> a big difference in time needed to save a system dump.
>
> (Does anyone know of a reason why copy_oldmem_page() would need
>  to use uncached addresses?)
>
> Diffed against 2.6.36-rc3

I had a similar patch somewhere in my private kernels,
yes it's a big win. I think it was simply a bug that was added
when ioremap was changed to default to uncached.

-Andi
-- 
ak@linux.intel.com -- Speaking for myself only.


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WARNING: multiple messages have this Message-ID (diff)
From: Andi Kleen <andi@firstfloor.org>
To: Cliff Wickman <public-cpw-sJ/iWh9BUns@plane.gmane.org>
Cc: public-kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@plane.gmane.org,
	public-mingo-X9Un+BFzKDI@plane.gmane.org,
	public-linux-kernel-u79uwXL29TY76Z2rM5mHXA@plane.gmane.org
Subject: Re: [PATCH] x86: copy_oldmem_page using cached addressing
Date: Wed, 08 Sep 2010 21:42:18 +0200	[thread overview]
Message-ID: <87eid4vx7p.fsf@basil.nowhere.org> (raw)
In-Reply-To: <E1OtMLz-0001yp-Ia@eag09.americas.sgi.com> (Cliff Wickman's message of "Wed, 08 Sep 2010 10:14:27 -0500")



Cliff Wickman <cpw-sJ/iWh9BUns@public.gmane.org> writes:

> From: Cliff Wickman <cpw-sJ/iWh9BUns@public.gmane.org>
>
> The copy of /proc/vmcore to a user buffer proceeds much faster
> if the kernel addresses memory as cached.
>
> With this patch we have seen an increase in transfer rate from less than
> 15MB/s to 80-460MB/s, depending on size of the transfer.  This makes
> a big difference in time needed to save a system dump.
>
> (Does anyone know of a reason why copy_oldmem_page() would need
>  to use uncached addresses?)
>
> Diffed against 2.6.36-rc3

I had a similar patch somewhere in my private kernels,
yes it's a big win. I think it was simply a bug that was added
when ioremap was changed to default to uncached.

-Andi
-- 
ak@linux.intel.com -- Speaking for myself only.


  parent reply	other threads:[~2010-09-08 19:42 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-09-08 15:14 [PATCH] x86: copy_oldmem_page using cached addressing Cliff Wickman
2010-09-08 15:14 ` Cliff Wickman
2010-09-08 19:19 ` Eric W. Biederman
2010-09-08 19:19   ` Eric W. Biederman
2010-09-09  7:48   ` Ingo Molnar
2010-09-09  7:48     ` Ingo Molnar
2010-09-08 19:42 ` Andi Kleen [this message]
2010-09-08 19:42   ` Andi Kleen
2010-09-09 11:57 ` [tip:x86/mm] x86, kdump: Change copy_oldmem_page() to use " tip-bot for Cliff Wickman

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