Messages in this thread | | | From | "Chen, Kenneth W" <> | Subject | RE: cfq performance gap | Date | Tue, 12 Dec 2006 21:23:31 -0800 |
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AVANTIKA R. MATHUR wrote on Tuesday, December 12, 2006 5:33 PM > >> rawio is actually performing sequential reads, but I don't believe it is > >> purely sequential with the multiple processes. > >> I am currently running the test with longer runtimes and will post > >> results once it is complete. > >> I've also attached the rawio source. > >> > > > > It's certainly the slice and idling hurting here. But at the same time, > > I don't really think your test case is very interesting. The test area > > is very small and you have 16 threads trying to read the same thing, > > optimizing for that would be silly as I don't think it has much real > > world relevance. > > Could a database have similar workload to this test?
No.
Not what I have seen with db workloads exhibits such pattern. There are basically two types of db workloads: one does transaction processing, and I/O pattern are truly random with large stride, both in the context of process and overall I/O seen at device level. A second one is decision making type of db queries. They does large sequential I/O within one process context.
This rawio test plows through sequential I/O and modulo each small record over number of threads. So each thread appears to be non-contiguous within its own process context, overall request hitting the device are sequential. I can't see how any application does that kind of I/O pattern.
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