Hi,
On Sat, 11 Aug 2007, Ingo Molnar wrote:
> the only relevant thing that comes to mind at the moment is that last
> week Peter noticed a buggy aspect of sleeper bonuses (in that we do not
> rate-limit their output, hence we 'waste' them instead of redistributing
> them), and i've got the small patch below in my queue to fix that -
> could you give it a try?
It doesn't make much of a difference. OTOH if I disabled the sleeper code
completely in __update_curr(), I get this:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3139 roman 20 0 1796 344 256 R 21.7 0.3 0:02.68 lt
3138 roman 20 0 1796 344 256 R 21.7 0.3 0:02.68 lt
3137 roman 20 0 1796 520 432 R 21.7 0.4 0:02.68 lt
3136 roman 20 0 1532 268 216 R 34.5 0.2 0:06.82 l
Disabling this code completely via sched_features makes only a minor
difference:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3139 roman 20 0 1796 344 256 R 20.4 0.3 0:09.94 lt
3138 roman 20 0 1796 344 256 R 20.4 0.3 0:09.94 lt
3137 roman 20 0 1796 520 432 R 20.4 0.4 0:09.94 lt
3136 roman 20 0 1532 268 216 R 39.1 0.2 0:19.20 l
> this is just a blind stab into the dark - i couldnt see any real impact
> from that patch in various workloads (and it's not upstream yet), so it
> might not make a big difference.
Can we please skip to the point, where you try to explain the intention a
little more?
If I had to guess that this is supposed to keep the runtime balance, then
it would be better to use wait_runtime to adjust fair_clock, from where it
would be evenly distributed to all tasks (but this had to be done during
enqueue and dequeue). OTOH this also had then a consequence for the wait
queue, as fair_clock is used to calculate fair_key.
IMHO current wait_runtime should have some influence in calculating the
sleep bonus, so that wait_runtime doesn't constantly overflow for tasks
which only run occasionally.
bye, Roman
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