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Subjectcfq performance gap
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Hi Jens, 

I've noticed a performance gap between the cfq scheduler and other io
schedulers when running the rawio benchmark.
Results from rawio on 2.6.19, cfq and noop schedulers:

CFQ:

procs device num read KB/sec I/O Ops/sec
----- --------------- ---------- ------- --------------
16 /dev/sda 16412 8338 2084
----- --------------- ---------- ------- --------------
16 16412 8338 2084

Total run time 0.492072 seconds


NOOP:

procs device num read KB/sec I/O Ops/sec
----- --------------- ---------- ------- --------------
16 /dev/sda 16399 29224 7306
----- --------------- ---------- ------- --------------
16 16399 29224 7306

Total run time 0.140284 seconds

The benchmark workload is 16 processes running 4k random reads.

Is this performance gap a known issue?
Thanks,
Avantika Mathur


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