Current Linux CPU scheduler doesnt recognize process aggregates while
allocating bandwidth. As a result of this, an user could simply spawn large
number of processes and get more bandwidth than others.
Here's a patch that provides fair allocation for all users in a system.
Some benchmark numbers with and without the patch applied follows:
user "vatsa" user "guest"
(make -s -j4 bzImage) (make -s -j20 bzImage)
2.6.20-rc5 472.07s (real) 257.48s (real)
2.6.20-rc5+fairsched 766.74s (real) 766.73s (real)
(Numbers taken on a 2way Intel x86_64 box)
Eventually something like this can be extended to do weighted fair share
scheduling for:
- KVM
- containers
- resource management
Salient features of the patch:
- Based on Ingo's RTLIMIT_RT_CPU patch [1]. Primary difference between
RTLIMIT_RT_CPU patch and this one is that this patch handles
starvation of lower priority tasks in a group and also accounting
is token based (rather than decaying avg).
- Retains existing one-runqueue-per-cpu design
- breaks O(1) (ouch!)
Best way to avoid this is to split runqueue to be per-user and
per-cpu, which I have not implemented to keep the patch simple.
- Fairsched aware SMP load balance NOT addressed (yet)
Comments/flames wellcome!
References:
1. http://kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.11-rc2/2.6.11-rc2-mm2/broken-out/rlimit_rt_cpu.patch
--
Regards,
vatsa
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