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SubjectRe: big ext3 sequential write improvement in 2.5.51-mm1 gone in 2.5.53-mm1?
Andrew Morton wrote:

> wrote:
>>Did you add a secret sauce to 2.5.59-mm2?
>I have not been paying any attention to the I/O scheduler changes for a
>couple of months, so I can't say exactly what caused this. Possibly Nick's
>batch expiry logic which causes the scheduler to alternate between reading
>and writing with fairly coarse granularity.
Yes, however tiobench doesn't mix the two. The batch_expire helps
probably by giving longer batches between servicing expired requests.
The deadline-np-42 patch also eliminates corner cases in which requests
could be starved for a long time. A large batch_expire as in mm2 is not
a good solution without my anticipatory scheduling stuff though as
writes really starve reads.

>> 10x sequential write improvement on ext3 for multiple tiobench threads.
>I _have_ been paying attention to the IO scheduler for the past few days.
>-mm5 will have the first draft of the anticipatory IO scheduler. This of
>course is yielding tremendous improvements in bandwidth when there are
>competing reads and writes.
>I expect it will take another week or two to get the I/O scheduler changes
>really settled down. Your assistance in thoroughly benching that would be
>>2.4.20aa1 8.24 7.21% 28.587 449134.11 0.10395 0.07086 114
>>2.5.59 9.50 5.50% 36.703 4310.62 0.00000 0.00000 173
>>2.5.59-mm2 35.28 17.69% 10.173 18950.56 0.01010 0.00000 199
I'm happy with that as long as they aren't too dependant on the phase of
the moon. The initial deadline scheduler had quite a lot of problems with
these workloads.

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