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

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Date:	Tue, 7 May 2013 08:25:01 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Robert Hancock <hancockrwd@...il.com>
Cc:	"Artem S. Tashkinov" <t.artem@...os.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Phillip Susi <psusi@...ntu.com>
Subject: Re: Abysmal HDD/USB write speed after sleep on a UEFI system

[+cc Phillip]

On Tue, Apr 30, 2013 at 9:19 PM, Robert Hancock <hancockrwd@...il.com> wrote:
> On 04/29/2013 10:47 PM, Bjorn Helgaas wrote:
>>
>> On Sat, Apr 27, 2013 at 4:10 AM, Artem S. Tashkinov <t.artem@...os.com>
>> wrote:
>>>>
>>>>
>>>> Did this problem ever get resolved?
>>>>
>>>
>>> Hello,
>>>
>>> Unfortunately, no. Out of curiosity I've tried booting kernel
>>> 3.9-rc8 in EUFI mode but it exhibits the same problem.
>>>
>>> Right after the boot:
>>>
>>> [root@...alhost ~]# dd if=/dev/zero of=test bs=64M count=3
>>> 3+0 records in
>>> 3+0 records out
>>> 201326592 bytes (201 MB) copied, 1.08544 s, 185 MB/s
>>>
>>> After suspend/resume:
>>>
>>> # dd if=/dev/zero of=test bs=64M count=3
>>> 3+0 records in
>>> 3+0 records out
>>> 201326592 bytes (201 MB) copied, 66.5392 s, 3.0 MB/s
>>>
>>> That's for my primary SATA-3 HDD.
>>>
>>> Forgive me my impudence but I believe debugging the USB stack is
>>> tangential to this problem. Something far deeper than USB support
>>> breaks, but so far no one has come even with the slightest clue of
>>> what that might be.
>>
>>
>> I tend to agree that it sounds like something deeper than USB is
>> broken.  I admit I'm just grasping at straws because I don't have any
>> good ideas yet.
>>
>> Here are three easy things you can try:
>>
>> 1) Collect "lspci -vvv -xxxx" output before and after the
>> suspend/resume to investigate the XHCI Unsupported Request errors.
>>
>> 2) Collect the contents of /proc/mtrr before and after the suspend/resume.
>>
>> 3) After the suspend/resume, 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 would suspect that Windows' complaint about the BIOS mucking up the MTRRs
> is likely the best hint. Likely Windows is detecting the problem and fixing
> it up on resume, thus it only complains about "reduced resume performance".
> If the MTRRs are messed up, then quite likely parts of RAM have become
> uncacheable, causing performance to get randomly slaughtered in various
> ways.
>
> From looking at the code it's not clear if we are checking/restoring the
> MTRR contents after resume. If not, maybe we should be.

I agree; the MTRR warning is a good hint.  Artem?

Phillip, I cc'd you because you have similar hardware and your
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1131468 report is
slightly similar.  Have you seen anything like this "reduced
performance after resume" issue?  If so, can you collect /proc/mtrr
contents before and after suspending?

Bjorn
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