On Fri, 2008-02-29 at 12:01 -0600, James Bottomley wrote: > I noticed that the current marvell sas driver wasn't performing very > well. It turns out that it's setting can_queue not in the SCSI host, > but in its own internal data structure, meaning it's always operating > with a global queue depth of one. This patch raises it to what the code > seemed to be intending ... although I think can_queue should be > MVS_CHIP_SLOT_SZ - 1 (without the divide by two)? > > The good news is that with this change, I'm getting a respectable > throughput on the fio hammer test; plus zapping random phy resets across > the disk triggers error handler recovery correctly (so far). > > I'm having less happy results with a SATAPI DVD ... it looks like the > initial IDENTIFY goes across just fine, but that we stall on the other > SCSI commands ... I'm still investigating this one. Actually, I've run into another problem with this patch applied. It looks like NCQ fails with ATA disks. What I see is that I/O goes fine until I get more than one command outstanding to the device, then the device stops responding. I can keep the I/O flowing if I clamp the device queue depth at 1. SAS disks seem to be fine ... I can get multiple outstanding commands to them correctly serviced. James -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
