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SubjectRe: [revert] mysql+oltp regression
Ingo Molnar wrote:
> * Gregory Haskins <ghaskins@novell.com> wrote:
>
>
>>>> Speaking of this: Another patch I submitted to you Ingo (had to do
>>>> with updating the load_weight inside task_setprio) seems to also
>>>> have this phenomenon: e.g. its technically correct but further
>>>> testing has revealed negative repercussions elsewhere. So please
>>>> ignore that patch (or revert if you already pulled in, but I don't
>>>> think you have). Ill try to look into this issue as well.
>>>>
>>> ok, under which thread/subject is that? Not queued in tip/sched/*
>>> yet, correct?
>>>
>>>
>> Here is the original thread:
>>
>> http://lkml.org/lkml/2008/7/3/416
>>
>> I do not believe you have queued it anywhere (public anyway) yet.
>>
>> Note I have already invalidated 1/2, and now I am retracting 2/2 as
>> well. (1/2 is actually a bogus patch, 2/2 is "technically correct"
>> but causes ripples in the load balancer that need to be sorted out
>> first.
>>
>
> ok, thanks. I'm curious, what are those ripple effects? Stability or
> performance?
>

Performance. I found it while working on my pi series (which fyi I
should have a v2 refresh for soon, probably today...i am hoping to get
some review feedback from you on that as well, time permitting of course ;).

Basically the behavior I was observing was that kernel builds via distcc
would cluster all the cc1 jobs on a single core. At first I thought my
pi-series was screwed up, but then I realized I had applied the patch
referenced above earlier in my development tree, and removing it allowed
pi to work fine.

I found the problem with in once boot cycle with ftrace (thanks
Steve!). Basically newidle balancing was always returning "no
imbalance" even though I had 32 cc1 threads on 1 core, and 3 idle
cores. Clearly not correct! So I think that by adjusting the load up,
we throw off the hysteresis built into the load averages and cause the
system to incorrectly think it's balanced. TBD.

-Greg


> Ingo
>


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