Messages in this thread | | | Date | Fri, 17 Apr 2009 22:11:09 +0400 | From | Vladislav Bolkhovitin <> | Subject | Re: [Scst-devel] ISCSI-SCST performance (with also IET and STGT data) |
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Bart Van Assche, on 04/04/2009 12:04 PM wrote: > On Thu, Apr 2, 2009 at 7:16 PM, Vladislav Bolkhovitin <vst@vlnb.net> wrote: >> Bart Van Assche, on 04/02/2009 12:14 AM wrote: >>> I have repeated some of these performance tests for iSCSI over IPoIB >>> (two DDR PCIe 1.0 ConnectX HCA's connected back to back). The results >>> for the buffered I/O test with a block size of 512K (initiator) >>> against a file of 1GB residing on a tmpfs filesystem on the target are >>> as follows: >>> >>> write-test: iSCSI-SCST 243 MB/s; IET 192 MB/s. >>> read-test: iSCSI-SCST 291 MB/s; IET 223 MB/s. >>> >>> And for a block size of 4 KB: >>> >>> write-test: iSCSI-SCST 43 MB/s; IET 42 MB/s. >>> read-test: iSCSI-SCST 288 MB/s; IET 221 MB/s. >> Do you have any thoughts why writes are so bad? It shouldn't be so.. > > By this time I have run the following variation of the 4 KB write test: > * Target: iSCSI-SCST was exporting a 1 GB file residing on a tmpfs filesystem. > * Initiator: two processes were writing 4 KB blocks as follows: > dd if=/dev/zero of=/dev/sdb bs=4K seek=0 count=131072 oflag=sync & > dd if=/dev/zero of=/dev/sdb bs=4K seek=131072 count=131072 oflag=sync & > > Results: > * Each dd process on the initiator was writing at a speed of 37.8 > MB/s, or a combined writing speed of 75.6 MB/s. > * CPU load on the initiator system during the test: 2.0. > * According to /proc/interrupts, about 38000 mlx4-comp-0 interrupts > were triggered per second. > > These results confirm that the initiator system was the bottleneck > during the 4 KB write test, not the target system.
If so with oflag=direct you should have a performance gain, because you will eliminate a data copy.
> Bart. > > ------------------------------------------------------------------------------ > _______________________________________________ > Scst-devel mailing list > Scst-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/scst-devel >
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