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

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Date:	Tue, 12 Feb 2013 20:13:33 +0000 (UTC)
From:	"Artem S. Tashkinov" <t.artem@...os.com>
To:	torvalds@...ux-foundation.org
Cc:	bhelgaas@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: Abysmal HDD/USB write speed after sleep on a UEFI system

Feb 13, 2013 01:32:53 AM, Linus Torvalds wrote:
On Tue, Feb 12, 2013 at 10:29 AM, Artem S. Tashkinov wrote:
>> Feb 12, 2013 11:30:20 PM, Linus Torvalds wrote:
>>>
>>>A few things to try to pinpoint:
>>>
>>> (a) Is it *only* write performance that suffers, or is it other
>>>performance too? Networking (DMA? Perhaps only writing *to* the
>>>network?)? CPU?
>>
>> I  've tested hdpard -tT --direct and the output on boot and after suspend
>> is quite similar.
>>
>> I  've also checked my network read/write speed, and it  's the same
>> ~ 100MBit/sec (I have no 1Gbit computers on my network
>> unfortunately).
>
>Ok. So it really sounds like just USB and HD writes. Which is quite
>odd, since they have basically nothing in common I can think of
>(except the obvious block layer issues).
>
>>> (b) the fact that it apparently happens with both SATA and USB
>>>implies that it    's neither, and is more likely something core like
>>>memory speed (mtrr, caching) or PCI (DMA, burst sizes, whatever).
>>
>> I  've no idea, please, check my bug report where I  've just added lots of
>> information including a diff between on boot and after suspend.
>
>I  'm not seeing anything particularly interesting there.
>
>Except why/how did the MSI address/data change for the SATA
>controller? The irq itself hasn  't changed.. There  's probably some sane
>reason for that too (it  's an odd encoding, maybe they code for the
>same thing), and there  's nothing like that for USB, so...
>
>And if it was irq problems, I  'd expect you to see it more for reads
>than for writes anyway. Along with a few messages about missed irqs
>and whatever.
>
>I'm stumped, and have no ideas. I can  't even begin to guess how this
>would happen. One thing to try is if it happens for all USB ports (you
>have multiple controllers) and I assume performance doesn  't come back
>if you unplug and replug the USB disk..

I've just plugged and unplugged my USB stick into all available hubs
(including a USB3 one, that is xhci_hcd) and I've got the same write speed
on all of them - around 930KB/sec (quite a weird number - as if I'm on USB
1.1) - lsusb says I'm happily running ehci_hcd/2p, 480M and xhci_hcd/2p,
5000M.

The only pattern that I see here is that write speed to real devices degrades,
tmpfs write speed stays the same:

$ dd if=/dev/zero of=test bs=32M count=32
32+0 records indegrade
32+0 records out
1073741824 bytes (1.1 GB) copied, 0.296323 s, 3.6 GB/s

Best regards,

Artem
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