Messages in this thread | | | Date | Wed, 31 Aug 2005 09:59:39 -0600 | From | jmerkey <> | Subject | Re: Where is the performance bottleneck? |
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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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