On 16/02/2016 15:33, Hannes Reinecke wrote:
On 02/16/2016 01:22 PM, John Garry wrote:
In high-datarate aging tests, it is found that
the SCSI framework can periodically
issue lu resets to the device. This is because scsi
commands begin to timeout. It is found that TASK SET
FULL may be returned many times for the same command,
causing the timeouts.
To overcome this, the queue depth for the device needs
to be reduced to 64 (from 256, set in
sas_slave_configure()).
Hmm. TASK SET FULL should cause the queue depth to be reduced
automatically, no?
Cheers,
Hannes
I need to double-check if Task set full reduces the depth, I don't think
it does.
Regardless I found we were getting a combination of commands being
retried due to Task Set Full and also SAS_QUEUE_FULL errors. For sure
the SAS_QUEUE_FULL task errors reduce the queue depth in
scsi_track_queue_full(). However I found it to be very slow in tracking,
and we were getting commands timing out before the queue depth fell enough.
It would be nice to change default queue depth in sas_slave_configure()
to a lower value so we can avoid this patch, but I am not sure if other
vendor's HBA performance would be affected. From looking at the history
of sas_slave_configure(), it would seem the value of 256 was inherited
from mpt2sas driver, so I'm not sure.
Cheers,
John
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