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

rwhron
2003-01-24T04:26:46Z

Andrew:
>> 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.

OK. The previous -mm I tested on the quad Xeon was 2.5.54-mm3, so if
Nick's batch expiry is more recent, it explains the "sudden" tiobench
divergence with Linus' tree.

>> Possibly Nick's
>> batch expiry logic which causes the scheduler to alternate between reading
>> and writing with fairly coarse granularity.

Nick:
> Yes, however tiobench doesn't mix the two. The batch_expire helps
> probably by giving longer batches between servicing expired requests.

Andrew:
>>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.

The mixed workloads I run that vary the most are "memory shortage" tests.

qsbench creates heavy swap load and simultaneous ed build. (small gnu package
"tar xzf/configure/make/make check").

Good numbers for this benchmark are open to interpretation, but more
ed builds in less time is better. The "secs" column is how long it took
for qsbench to do it's thing.

kernel ed_builds secs secs/build
2.4.20-rc2-ac1-rmap15-O1 38 373 9.82
2.4.19-rmap15 50 445 8.90
2.4.20-rc2aa1-4m 47 597 12.70
2.4.20-pre8aa1 47 598 12.72
2.4.20aa1 50 603 12.06
2.4.20-rc1-jam1 51 604 11.84
2.4.20-jam2 50 609 12.18
2.4.20-pre11aa1o1 58 615 10.60
2.4.20-pre11aa1 55 632 11.49
2.4.20-rc2aa1 55 648 11.78
2.4.20-rc1aa1 61 678 11.11
2.4.20-rc4 57 743 13.04
2.5.51-mm2 63 761 12.08
2.5.58 87 809 9.30
2.4.19-ck13 86 822 9.56
2.4.20-pre10 75 831 11.08
2.4.20-rc1 85 938 11.04
2.5.50 110 978 8.89
2.5.50bk8 107 984 9.20
2.5.51-mm1 87 985 11.32
2.5.46-mm2 85 1000 11.76
2.5.59 119 1088 9.14
2.5.55 127 1127 8.87
2.5.54-mm2 73 1135 15.55
2.5.52-mm2 101 1202 11.90
2.5.59-mm2 139 1263 9.09
2.5.53-mm1 107 1297 12.12
2.5.54-mm3 97 1361 14.03
2.5.52-wli-1 200 1775 8.88
2.5.56 222 1978 8.91
2.5.52bk7 232 2085 8.99
2.5.49-mm1 248 2731 11.01
2.5.39 346 2949 8.52
2.5.44-mm5 348 2996 8.61
2.5.42 408 3528 8.65
2.5.44-mm6 342 3680 10.76
2.5.43-mm2 475 4209 8.86
2.5.40-mm1 706 6131 8.68

--
Randy Hron