512 is not enough. It has to be larger. I just tried 512 and it still
limits the data rates.
Jeff
Jens Axboe wrote:
On Wed, Aug 31 2005, jmerkey wrote:
I have seen an 80GB/sec limitation in the kernel unless this value is
changed in the SCSI I/O layer
for 3Ware and other controllers during testing of 2.6.X series kernels.
Change these values in include/linux/blkdev.h and performance goes from
80MB/S to over 670MB/S on the 3Ware controller.
//#define BLKDEV_MIN_RQ 4
//#define BLKDEV_MAX_RQ 128 /* Default maximum */
#define BLKDEV_MIN_RQ 4096
#define BLKDEV_MAX_RQ 8192 /* Default maximum */
That's insane, you just wasted 1MiB of preallocated requests on each
queue in the system!
Please just do
# echo 512 > /sys/block/dev/queue/nr_requests
after boot for each device you want to increase the queue size too. 512
should be enough with the 3ware.
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