linux-kernel - Re: [PATCH] x86, efi: Break up large initrd reads

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Date:	Tue, 13 Dec 2011 10:26:23 -0800
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	"H. Peter Anvin" <hpa@...or.com>,
	Maarten Lankhorst <m.b.lankhorst@...il.com>
CC:	Matt Fleming <matt@...sole-pimps.org>,
	Matthew Garrett <mjg@...hat.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	Mike Waychison <mikew@...gle.com>,
	Andi Kleen <andi@...stfloor.org>,
	Peter Jones <pjones@...hat.com>
Subject: Re: [PATCH] x86, efi: Break up large initrd reads

On 12/12/2011 03:10 PM, H. Peter Anvin wrote:
> On 11/25/2011 12:48 AM, Matt Fleming wrote:
>> On Fri, 2011-11-25 at 02:37 +0100, Maarten Lankhorst wrote:
>>> The efi boot stub tries to read the entire initrd in 1 go,
>>> however some efi implementations hang if too much if asked
>>> to read too much data at the same time. After some
>>> experimentation I found out that my asrock p67 board will
>>> hang if asked to read chunks of 4mb, so use a safe value.
>>>
>>> From elilo source code:
>>> /*
>>>  * We load by chunks rather than a single big read because
>>>  * early versions of EFI had troubles loading files
>>>  * from floppies in a single big request.  Breaking
>>>  * the read down into chunks of 4KB fixed that
>>>  * problem. While this problem has been fixed, we still prefer
>>>  * this method because it tells us whether or not we're making
>>>  * forward progress.
>>>  */
>>>
>>> While the comment says 4KB, it's using 4 * EFI_PAGE_SIZE (16KB),
>>> so I went by the safest route of following elilo here.
>>>
> 
> I'm going to NAK this, because I think the performance impact is too
> severe.  I would like to set the cap at 1 MiB for now, unless we can
> identify platforms where *that* is known to fail.
> 
> Maarten, would you be willing to rev your patch?  Furthermore, please
> make the maximum chunksize a define.
> 

One more thing, Maarten: could you please provide the full DMI
information of the affected system?

	-hpa

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