[ewg] Re: [Scst-devel] SRP performance in SCST
On Mon, Mar 10, 2008 at 3:20 PM, Doron Shoham [EMAIL PROTECTED] wrote: I used the following commands: for write commands: sgp_dd of=/dev/sg1 if=/dev/zero bs=512 bpt=from 2-512 thr=8 time=1 count=20M for read commands sgp_dd if=/dev/sg1 of=/dev/null bs=512 bpt=from 2-512 thr=8 time=1 count=20M And the results are (all in MB/s): bpt:2 4 8 16 32 64 128 256 512 Write 22.541.480.6160 275 443 570 740 810 Read42 80 170 313 550 940 12001312 1300 What can be the reason for such difference between the bandwidth of Read and Write commands? Can you please try to use direct I/O instead of buffered I/O ? Bart. ___ ewg mailing list ewg@lists.openfabrics.org http://lists.openfabrics.org/cgi-bin/mailman/listinfo/ewg
[ewg] Re: [Scst-devel] SRP performance in SCST
Bart Van Assche wrote: On Mon, Mar 10, 2008 at 3:20 PM, Doron Shoham [EMAIL PROTECTED] wrote: I used the following commands: for write commands: sgp_dd of=/dev/sg1 if=/dev/zero bs=512 bpt=from 2-512 thr=8 time=1 count=20M for read commands sgp_dd if=/dev/sg1 of=/dev/null bs=512 bpt=from 2-512 thr=8 time=1 count=20M And the results are (all in MB/s): bpt:2 4 8 16 32 64 128 256 512 Write 22.541.480.6160 275 443 570 740 810 Read42 80 170 313 550 940 1200 13121300 What can be the reason for such difference between the bandwidth of Read and Write commands? Can you please try to use direct I/O instead of buffered I/O ? Bart. I have tried to use dio but when the bpt was 128 (or higher) I got the following error: echo 1 /proc/scsi/sg/allow_dio sgp_dd if=/dev/sg1 of=/dev/null bs=512 bpt=128 thr=8 time=1 count=5M dio=1 time to transfer data was 2.236290 secs, 1200.36 MB/sec 5242880+0 records in 5242880+0 records out Direct IO requested but incomplete 40960 times Doron ___ ewg mailing list ewg@lists.openfabrics.org http://lists.openfabrics.org/cgi-bin/mailman/listinfo/ewg
[ewg] Re: [Scst-devel] SRP performance in SCST
On Mon, Mar 10, 2008 at 3:42 PM, Doron Shoham [EMAIL PROTECTED] wrote: Bart Van Assche wrote: Can you please try to use direct I/O instead of buffered I/O ? Bart. I have tried to use dio but when the bpt was 128 (or higher) I got the following error: echo 1 /proc/scsi/sg/allow_dio sgp_dd if=/dev/sg1 of=/dev/null bs=512 bpt=128 thr=8 time=1 count=5M dio=1 time to transfer data was 2.236290 secs, 1200.36 MB/sec 5242880+0 records in 5242880+0 records out Direct IO requested but incomplete 40960 times I'm not familiar with the /proc/scsi/sg/allow_dio entry. I was referring to options like iflag=direct or oflag=direct for dd -- all performance tests I have performed in the past were with dd and xdd. Without direct I/O, read tests use Linux' buffering. If the amount of data being read is less than the available RAM, buffered I/O tests only measure how fast Linux can copy data in RAM. Bart. ___ ewg mailing list ewg@lists.openfabrics.org http://lists.openfabrics.org/cgi-bin/mailman/listinfo/ewg
