Re: [patch 0/9] sched: use runnable load avg in balance

[Alex Shi]

Ingo & Peter:

How are you?
I know you are very very busy since services for wide key kernel parts.
So hope this email don't disturb you. :)

PJT's runnable load was introduced into kernel from 3.8 kernel. But
besides increase longer code path, it does nothing help now.

This patch try to enable the runnable load into scheduler balance. Most
of this patchset are bug fixing related except 6~8th which are direct
service for introducing runnable load into balance.
The patchset was talked in LKML from last Nov, adopted many suggestions
from PTJ, MikeG, Morten, PeterZ etc. Also tested on x86 and arm
platforms, both got positive feedback.

With this patchset, CFS scheduler will has better and stabler
performance on hackbench, sysbench, pgbench. etc benchmarks. You will
like the performance number which mentioned in last emails.

I appreciated for any further review and comments!

Wish you all best!
Alex


On 06/07/2013 03:20 PM, Alex Shi wrote:
> Peter&Ingo:
> 
> v8: add a marco div64_ul and used it in task_h_load()
> v7: rebasing on tip/sched/core tree.
> 
> I tested on Intel core2, NHM, SNB, IVB, 2 and 4 sockets machines with
> benchmark kbuild, aim7, dbench, tbench, hackbench, oltp, and netperf
> loopback etc. 
> 
> On SNB EP 4 sockets machine, the hackbench increased about 50%, and
> result become stable. on other machines, hackbench increased about
> 2~10%. oltp increased about 30% in NHM EX box. netperf loopback also
> increased on SNB EP 4 sockets box. 
> No clear changes on other benchmarks.
> 
> Michael Wang gotten better performance on pgbench on his box with this
> patchset. https://lkml.org/lkml/2013/5/16/82
> 
> And Morten tested previous version with better power consumption.
> http://comments.gmane.org/gmane.linux.kernel/1463371
> 
> Changlong found ltp cgroup stress testing get faster on SNB EP
> machine with the last patch.  https://lkml.org/lkml/2013/5/23/65
> ---
> 3.10-rc1          patch1-7         patch1-8
> duration=764   duration=754   duration=750
> duration=764   duration=754   duration=751
> duration=763   duration=755   duration=751
> 
> duration means the seconds of testing cost.
> ---
> 
> Jason also found java server load benefited on his 8 sockets machine
> with last patch. https://lkml.org/lkml/2013/5/29/673
> ---
> When using a 3.10-rc2 tip kernel with patches 1-8, there was about a 40%
> improvement in performance of the workload compared to when using the
> vanilla 3.10-rc2 tip kernel with no patches. When using a 3.10-rc2 tip
> kernel with just patches 1-7, the performance improvement of the
> workload over the vanilla 3.10-rc2 tip kernel was about 25%.
> ---
> 
> We also tried to include blocked load avg in balance. but find many
> benchmark performance drop a lot! Seems accumulating current
> blocked_load_avg into cpu load isn't a good idea. Because:
> 1, The blocked_load_avg is decayed same as runnable load, sometime is far
> bigger than runnable load, that drive tasks to other idle or slight
> load cpu, than cause both performance and power issue. But if the
> blocked load is decayed too fast, it lose its effect. 
> 2, Another issue of blocked load is that when waking up task, we can not 
> know blocked load proportion of the task on rq. So, the blocked load is
> meaningless in wake affine decision.  
> 
> According to above problem, we can not figure out a right way now to use 
> blocked_load_avg in balance.
> 
> Since using runnable load avg in balance brings much benefit on
> performance and power. and this patch was reviewed for long time.
> So seems it's time to let it be clobbered in some sub tree, like 
> tip or linux-next.  Any comments?
> 
> Regards
> Alex
> 


-- 
Thanks
    Alex
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