On Tue, Feb 2, 2010 at 9:53 AM, Jens Axboe <jens.axboe@xxxxxxxxxx> wrote: > I committed a fix for this, it'll do it automatically now if you use > latest -git. A quick test here on my desktop machine: > > fio --bs=4k --size=64G --buffered=1 --rw=write --verify=0 > --name=/dev/null --gtod_reduce=1 --disk_util=0 > > 10378MB/s > > fio --bs=512 --size=8G --buffered=1 --rw=write --verify=0 > --name=/dev/null --gtod_reduce=1 --disk_util=0 > > 1306MB/s > > dd if=/dev/zero of=/dev/null bs=4k count=16M > 68719476736 bytes (69 GB) copied, 9,71235 s, 7,1 GB/s > > dd if=/dev/zero of=/dev/null bs=512 count=8M > 4294967296 bytes (4,3 GB) copied, 3,3574 s, 1,3 GB/s > > So the same for 512b buffers, fio is much quicker for 64k (must be due > to proper aligning). I'll boot the big box and see what that says. Thanks, this helps: the ratio of fio to dd runtime is now reduced to 1.25 for a block size of 512 bytes and 0.96 for a block size of 4096 bytes. $ count=$((2**25)); for bs in 512 4096; do size=$((count*bs)); dd if=/dev/zero of=/dev/null bs=$bs count=$count 2>&1|grep copied; fio --bs=$bs --size=$size --buffered=1 --rw=write --verify=0 --name=dev-null --filename=/dev/null 2>&1|grep runt; done 17179869184 bytes (17 GB) copied, 22.1017 s, 777 MB/s write: io=16,384MB, bw=621MB/s, iops=1,272K, runt= 26381msec 137438953472 bytes (137 GB) copied, 27.5793 s, 5.0 GB/s write: io=128GB, bw=4,964MB/s, iops=1,271K, runt= 26407msec Bart. -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
