Re: SATA kernel-buffered read VERY slow (not raid, Promise TX300card); 2.6.23.1(vanilla)

[Mikael Pettersson]

Linda Walsh writes:
 > Robert Hancock wrote:
 > > Linda Walsh wrote:
 > >> Alan Cox wrote:
 > >>>> rate began falling; at 128k block-reads-at-a-time or larger, it 
 > >>>> drops below
 > >>>> 20MB/s (only on buffered SATA).
 > >>> Try disabling NCQ - see if you've got a drive with the 'NCQ = no
 > >>> readahead' flaw.
 > > http://linux-ata.org/faq.html#ncq
 > ---
 >     When drive initializes, dmesg says it has NCQ (depth 0/32)
 >     Reading the queue_depth under /sys, shows a queuedepth of "1".
 > 
 > But more importantly -- I notice a chronic error message associate
 > with this drive that may be causing some or all of the problem:
 > ---
 > Jan  2 20:06:10 Ishtar kernel: ata1.00: exception Emask 0x0 SAct 0x0 
 > SErr 0x0 action 0x2
 > Jan  2 20:06:10 Ishtar kernel: ata1.00: port_status 0x20080000
 > Jan  2 20:06:10 Ishtar kernel: ata1.00: cmd 
 > c8/00:10:30:06:03/00:00:00:00:00/e0 tag 0 cdb 0x0 data 8192 in
 > Jan  2 20:06:10 Ishtar kernel:          res 
 > 50/00:00:3f:06:03/00:00:00:00:00/e0 Emask 0x2 (HSM violation)
 > Jan  2 20:06:13 Ishtar kernel: ata1: limiting SATA link speed to 1.5 Gbps
 > Jan  2 20:06:13 Ishtar kernel: ata1.00: exception Emask 0x0 SAct 0x0 
 > SErr 0x0 action 0x6
 > Jan  2 20:06:13 Ishtar kernel: ata1.00: port_status 0x20080000
 > Jan  2 20:06:13 Ishtar kernel: ata1.00: cmd 
 > c8/00:10:00:8b:04/00:00:00:00:00/e0 tag 0 cdb 0x0 data 8192 in
 > Jan  2 20:06:13 Ishtar kernel:          res 
 > 50/00:00:0f:8b:04/00:00:00:00:00/e0 Emask 0x2 (HSM violation)
 > Jan  2 20:06:14 Ishtar kernel: ata1: exception Emask 0x10 SAct 0x0 SErr 
 > 0x0 action 0x3
 > Jan  2 20:06:14 Ishtar kernel: ata1: hotplug_status 0x80
 > Jan  2 20:06:15 Ishtar kernel: ata1: exception Emask 0x10 SAct 0x0 SErr 
 > 0x0 action 0x3
 > Jan  2 20:06:15 Ishtar kernel: ata1: hotplug_status 0x80
 > ---
 > What da heck?

Looks like the Promise ASIC SG bug. Apply
<http://user.it.uu.se/~mikpe/linux/patches/sata_promise/patch-sata_promise-1-asic-sg-bug-fix-v3-2.6.23>
and let us know if things improve.

/Mikael
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