Executive question: Why does 2.5.62-mm2 have higher sequential
write latency than 2.5.61-mm1?
tiobench numbers on uniprocessor single disk IDE:
The cfq scheduler (2.5.62-mm2 and 2.5.61-cfq) has a big latency
regression.
2.5.61-mm1 (default scheduler (anticipatory?))
2.5.61-mm1-cfq elevator=cfq
2.5.62-mm2-as anticipatory scheduler
2.5.62-mm2-dline elevator=deadline
2.5.62-mm2 elevator=cfq
Thr MB/sec CPU% avg lat max latency
2.5.61-mm1 8 15.68 54.42% 5.87 ms 2.7 seconds
2.5.61-mm1-cfq 8 9.60 15.07% 7.54 393.0
2.5.62-mm2-as 8 14.76 52.04% 6.14 4.5
2.5.62-mm2-dline 8 9.91 13.90% 9.41 .8
2.5.62-mm2 8 9.83 15.62% 7.38 408.9
2.4.21-pre3 8 10.34 27.66% 8.80 1.0
2.4.21-pre3-ac4 8 10.53 28.41% 8.83 .6
2.4.21-pre3aa1 8 18.55 71.95% 3.25 87.6
For most thread counts (8 - 128), the anticipatory scheduler has roughly
45% higher ext2 sequential read throughput. Latency was higher than
deadline, but a lot lower than cfq.
For tiobench sequential writes, the max latency numbers for 2.4.21-pre3
are notably lower than 2.5.62-mm2 (but not as good as 2.5.61-mm1).
This is with 16 threads.
Thr MB/sec CPU% avg lat max latency
2.5.61-mm1 16 18.30 81.12% 9.159 ms 6.1 seconds
2.5.61-mm1-cfq 16 18.03 80.71% 9.086 6.1
2.5.62-mm2-as 16 18.84 84.25% 8.620 47.7
2.5.62-mm2-dline 16 18.53 84.10% 8.967 53.4
2.5.62-mm2 16 18.46 83.28% 8.521 40.8
2.4.21-pre3 16 16.20 65.13% 9.566 8.7
2.4.21-pre3-ac4 16 18.50 83.68% 8.774 11.6
2.4.21-pre3aa1 16 18.49 88.10% 8.455 7.5
Recent uniprocessor benchmarks:
http://home.earthlink.net/~rwhron/kernel/latest.html
More uniprocessor benchmarks:
http://home.earthlink.net/~rwhron/kernel/k6-2-475.html
-- Randy Hron http://home.earthlink.net/~rwhron/kernel/bigbox.html latest quad xeon benchmarks: http://home.earthlink.net/~rwhron/kernel/blatest.html- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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