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Subject[REPORT] 2.6.21.1 vs 2.6.21-sd046 vs 2.6.21-cfs-v6
Date
i list,

meanwhile I've redone my numbercrunching tests with the following kernels:
2.6.21.1 (mainline)
2.6.21-sd046
2.6.21-cfs-v6
running on a dualcore x86_64.
[I will run the same test with 2.6.21.1-cfs-v7 over the next days,
likely tonight]

The tests consist of 3 tasks (named LTMM, LTMB and LTBM). The only
I/O they do is during init and for logging the results, the rest
is just floating point math.

There are 3 scenarios:
j1 - all 3 tasks run sequentially
/proc/sys/kernel/sched_granularity_ns=4000000
/proc/sys/kernel/rr_interval=16
j3 - all 3 tasks run in parallel
/proc/sys/kernel/sched_granularity_ns=4000000
/proc/sys/kernel/rr_interval=16
j3big - all 3 tasks run in parallel with timeslice extended
by 2 magnitudes (not run for mainline)
/proc/sys/kernel/sched_granularity_ns=400000000
/proc/sys/kernel/rr_interval=400
All 3 tasks are run while the system does nothing else except for
the "normal" (KDE) daemons. The system had not been used for
interactive work during the tests.

I'm giving user time as provided by the "time" cmd followed by wallclock time
(all values in seconds).

LTMM
j1 j3 j3big
2.6.21-cfs-v6 5655.07/ 5682 5437.84/ 5531 5434.04/ 8072
2.6.21-sd-046 5556.44/ 5583 5446.86/ 8037 5407.50/ 8274
2.6.21.1 5417.62/ 5439 5422.37/ 7132 na /na

LTMB
j1 j3 j3big
2.6.21-cfs-v6 7729.81/ 7755 7470.10/10244 7449.16/10186
2.6.21-sd-046 7611.00/ 7626 7573.16/10109 7458.10/10316
2.6.21.1 7438.31/ 7461 7620.72/11087 na /na

LTBM
j1 j3 j3big
2.6.21-cfs-v6 7720.70/ 7746 7567.09/10362 7464.17/10335
2.6.21-sd-046 7431.06/ 7452 7539.83/10600 7474.20/10222
2.6.21.1 7452.80/ 7481 7484.19/ 9570 na /na

LTMM+LTMB+LTBM
j1 j3 j3big
2.6.21-cfs-v6 21105.58/21183 20475.03/26137 20347.37/28593
2.6.21-sd-046 20598.50/20661 20559.85/28746 20339.80/28812
2.6.21.1 20308.73/20381 20527.28/27789 na /na


User time apparently is subject to some variance. I'm particularly surprised
by the wallclock time of scenario j1 and j3 for case LTMM with 2.6.21-cfs-v6.
I'm not sure what to make of this, i.e. whether I had happening something
else on my machine during j1 of LTMM -- that's always been the first test
I ran and it might be that there were still some other jobs running after
the initial boot.

Assuming scenario j1 does constitute the "true" time each task requires and
also assuming each scheduler makes maximum use of the available CPUs (the
tests involve very little I/O) one could compute the expected wallclock time.
However since I suspect the j1 figures of LTMM to be somewhat "dirty" I'll
refrain from it.

However from these figures it seems as if sd does provide for the fairest
(as in equal share for all) scheduling among the 3 schedulers tested.

Best,
Michael
--
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