Here's one thing that will help you....
in the lpfc driver (in rev 8.0.13 - the file is lpfc_fcp.c), in the
scsi_driver_template structure - add the field:
.max_sectors = 0xFFFF,
As of 2.6.10, the kernel started paying attention to this field, which the
emulex driver, as of that time, didn't set. The result was the kernel
dropped back to a default max_sectors of 1024 - which results in a 512k max.
The lpfc driver was updated in rev 8.0.29 with this change.
Caveat is : Even with this change, you must be using O_DIRECT to get high
bandwidth. Otherwise, the upper layers will segment the requests (if I
remember right, we had a hard time making a "normal" config exceed 256k).
-- james s
Martin W. Schlining III wrote:
I am running a program on my Linux box which is asking for 2M IO (reads
and writes) with the file handle being opened with the O_DIRECT flag.
However, the IO being put out on the wire is no larger than 512K. My
target device is the SCSI block device (/dev/sdb in this case). What is
preventing me from getting large IO through the SCSI block layer? How
can I fix it?
The sg device can achieve the 2M IO size, so I know its at least
possible. How can I improve the IO size for the SCSI block layer?
Details:
Dell 2850 server with dual Xeons, 1G RAM
OS: Linux racerx 2.6.11.4-21.10-smp #1 SMP Tue Nov 29 14:32:49 UTC 2005
x86_64 x86_64 x86_64 GNU/Linux
Emulex LP11000 Fibre Channel HBA using driver version 8.0.13 (changing
the driver hasn't helped, so far)
I set the lookahead value pretty large to improve read performance
(hdparm -a)
The scheduler for this device is anticipatory.
Any ideas?
Thanks,
Martin Schlining
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