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Date: Wed, 19 Mar 2008 18:08:07 -0700 From: Jeremy Higdon <jeremy@....com> To: David Chinner <dgc@....com> Cc: lkml <linux-kernel@...r.kernel.org> Subject: Re: Buffered I/O to block device very slow and other SCSI issues... On Thu, Mar 20, 2008 at 10:16:54AM +1100, David Chinner wrote: > 4p ia64, 24GB RAM, 2.6.25-rc3, qla1280, 15krpm scsi disk. > > Direct I/O: > > dgc@...gie:~/xfstests$ sudo dd if=/dev/zero of=/dev/sdb6 bs=1024k count=1024 oflag=direct > 1024+0 records in > 1024+0 records out > 1073741824 bytes (1.1 GB) copied, 27.8974 s, 38.5 MB/s > > Doing approximately 80 512k I/os per second (disk bandwidth). > > Buffered I/O: > > dgc@...gie:~/xfstests$ sudo dd if=/dev/zero of=/dev/sdb6 bs=1024k count=4096 > 4096+0 records in > 4096+0 records out > 4294967296 bytes (4.3 GB) copied, 427.872 s, 10.0 MB/s How big is sdb6? How many '2's do you see in factor `cat /sys/block/sdb/sdb6/size` > I also suspect that CTQ has not been set up correctly on this > kernel, because: > > $ cat /sys/block/sdb/device/queue_depth > 3 > $ ls -l /sys/block/sdb/device/queue_depth > -r--r--r-- 1 root root 0 Mar 20 09:59 /sys/block/sdb/device/queue_depth > $ > > It appears to be hard coded to 3 and can't be changed.... That's a bug in the qla1280 driver. I thought that had gotten fixed. It's looking at the wrong mailbox register after setting device parameters. jeremy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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