Re: big ext3 sequential write improvement in 2.5.51-mm1 gone in 2.5.53-mm1?

[Nick Piggin <piggin@cyberone.com.au>]

Andrew Morton wrote:

>rwhron@earthlink.net 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.
>>
>
>OK...  
>
>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
>appreciated.
>
>
>>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
>>
>
>boggle.
>
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.