ahcich timeouts, only with ahci, not with ataahci

[Harald Schmalzbauer]

Hello,

I'm frequently getting my machine locked with ahcichX timeouts:
ahcich2: Timeout on slot 0
ahcich2: is 00000000 cs 00000001 ss 00000000 rs 00000001 tfd c0 serr 
00000000
ahcich2: Timeout on slot 8
ahcich2: is 00000000 cs 00000100 ss 00000000 rs 00000100 tfd c0 serr 
00000000
ahcich2: Timeout on slot 8
ahcich2: is 00000000 cs fffff07f ss ffffff7f rs ffffff7f tfd c0 serr 
00000000
...

This happens when backup over GbE overloads ZFS/HDD capabilities.
I reduced vfs.zfs.txg.timeout to 1 to prevent the machine from locking 
up almost immediately, but from it still happens.
When I don't use ahci but ataahci (the old driver if I understand things 
correct) I also see the ZFS burst write congestion, but this doesn't 
lead to controller timeouts, thus blocking the machine.

Sometimes the machine recovers from the disk lock, but most often I have 
to reboot.

Kernel is from Feb. 19, so recent ahci improovements are active.
Controller is ICH9R with 3 Samsung F3 SpinPoints.

Any ideas how to work arround the hangs other than using the old ahci 
driver?

Thanks,

-Harry

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