[lkml]   [2005]   [Aug]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: Where is the performance bottleneck?
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.

Jens Axboe

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-08-31 19:13    [W:0.064 / U:0.072 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site