zhao, forrest wrote: > On Tue, 2006-05-16 at 19:49 +0900, Tejun Heo wrote: >> I don't know the workload of iozone. But NCQ shines when there are many >> concurrent IOs in progress. A good real world example would be busy >> file-serving web server. It generally helps if there are multiple IO >> requests. If iozone is single-threaded (IO-wise), try to run multiple >> copies of them and compare the results. >> >> Also, you need to pay attention to IO schedule in use, IIRC as and cfq >> are heavily optimized for single-queued devices and might not show the >> best performance depending on workload. For functionality test, I >> usually use deadline. It's simpler and usually doesn't get in the way, >> which, BTW, may or may not translate into better performance. >> > Tejun, > > I run iozone with 8 concurrent threads. From my understanding, NCQ > should at least provide the same throughput as non-NCQ. But the attached > test result showed that NCQ has the lower throughput compared with non- > NCQ. > > The io scheduler is anticipatory. > The kernel without NCQ is 2.6.16-rc6, the kernel with NCQ is #upstream. > > The current problem is that I don't know where the bottleneck is, block > I/O layer, SCSI layer, device driver layer or hardware problem...... AFAIK, anticipatory doesn't interact very well with queued devices. Can you try with deadline? -- tejun - : send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
