Re: Strange IO behaviour on wakeup from sleep
From: Benjamin Herrenschmidt
Date: Wed Oct 27 2004 - 17:53:23 EST
On Wed, 2004-10-27 at 07:18 -0700, Zachary Amsden wrote:
> I would tend to be very suspicious of DMA not being restored correctly
> because on some systems, prior to or during suspend, DMA may be shutdown
> to conserve power. There are changes afloat that touch suspend/resume,
> and there have been historical problems with DMA not being restored
> properly after wakeup on some laptops.
DMA is restored, and the resulting is way slower than what PIO would
explain anyway. I get less than 100Kb/sec !
(I wrote the IDE suspend/resume code and the driver for this chipset, so
I'm fairly sure that side is ok, it didn't change for a while, but I'll
double check in case Bart latest updates broke something).
> Although this may be another shot in the dark, it might rule out the DMA
> problem: try cat /proc/ide/yourchipset before and after suspend and
> note any changes. Failing that, use hdparm to turn off DMA before
> suspend and see if the performance suffers to the same degree as after
> wakeup.
Tried all of that.
Ben.
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