linux-kernel - Re: Abysmal HDD/USB write speed after sleep on a UEFI system

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Message-ID: <CAErSpo6UkVhSf+nFW4zwJLBQw_0RQ5H9Bv-UuQRb6zdwsFPw4g@mail.gmail.com>
Date:	Wed, 6 Mar 2013 17:17:26 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	"Artem S. Tashkinov" <t.artem@...os.com>
Cc:	stern@...land.harvard.edu, torvalds@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	rjw@...k.pl
Subject: Re: Abysmal HDD/USB write speed after sleep on a UEFI system

On Tue, Feb 26, 2013 at 12:14 PM, Artem S. Tashkinov <t.artem@...os.com> wrote:
> Feb 27, 2013 12:47:01 AM, Bjorn Helgaas wrote:
> On Mon, Feb 25, 2013 at 11:35 PM, Artem S. Tashkinov wrote:
>>> Feb 26, 2013 03:57:52 AM, Bjorn Helgaas wrote:
>>>>
>>>>Where are we at with this, Artem?  I assume it's still a problem.
>>>>
>>>
>>> Yes, it is, Bjorn.
>>>
>>> In order to eliminate this problem I switched back to MBR yesterday, because
>>> so far I haven't received any instructions or guidance as to how I can debug
>>> it further. I'm absolutely sure USB write speed is just another manifestation of
>>> it so I decided not to debug USB specifically (it just doesn't make too much
>>> sense).
>>>
>>> What I see is that something terribly wrong is going on but if Linus has no ideas
>>> I, as an average Joe, don't have a slightest clue as to what I can do.
>>>
>>> The bug report with necessary, but seemingly useless information, can be
>>> found here: https://bugzilla.kernel.org/show_bug.cgi?id=53551
>>>
>>> If anyone comes up with new ideas I can quickly try UEFI again now that I
>>> have two HDDs at my disposal (the old one is formatted as GPT, the new one is
>>> MBR).
>>
>>The ideas I saw are:
>>
>>1) Figure out whether it ever worked.  If an older kernel worked
>>correctly and a newer one is broken, bisection is at least a
>>possibility.  You mentioned that it did work before (Feb 12), but in
>>the past you never suspended twice in one boot session, whereas maybe
>>you did when seeing the problem?
>
> This is difficult to say since the first kernel I tried to run in EUFI mode was
> 3.7.x, so I've no idea if any previous ones ever worked.
>
>>
>>2) Try the "setpci" to set the MSI address back to the original value
>>to see if it makes a difference (see my Feb 12 message).
>
> I will try it soon and report back to you.
>
>>
>>3) Collect "lspci -vvv -xxxx" output to investigate the XHCI
>>Unsupported Request errors.
>>
>>4) Use usbmon to collect traces before and after the suspend.
>
> Likewise. Still I don't quite understand why you are persistent in your
> desire to investigate USB controllers specifically - my problem affects
> all storage devices that I have.

Well, in the absence of good ideas about what's going on, I guess we
have to pursue even the bad ideas that don't seem like they'd be
related :)  Speaking of bad ideas, any news on 2) and 3) above?

You mentioned in the bugzilla that Windows complains about MTRRs being
changed across the S4 sleep state transition.  I don't think Linux
looks for such a change.  You could try looking at /proc/mtrr before
and after the suspend/resume to see if anything changed there.  It
looks like there's even support for *writing* the MTRRs via
/proc/mtrr, so if anything did change, you could also try changing it
back.

Bjorn
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