On Thu, Aug 26, 2010 at 12:19 PM, Venkatesh Pallipadi <venki@google.com> wrote:
Venkatesh,
Thanks for your detailed response. I admit complete ignorance of
the actual logic of the complicated cpu_power computations (or indeed,
any other part of the scheduler code). I'm just looking at it from the
perspective of bug-hunting in an unfamiliar piece of code. I think the
three ways we've so far identified the cpu_power can be zero so far
(all three would be extremely low probability events admittedly) are
warning signs that the code is trying to do a bit too much. It seems
to be rather difficult to prove correctness of the math or the
synchronization for my taste. Is there a clear and present use-case
which driving all these complicated computations ?
For one thing, I don't understand the reason for recomputing
cpu_power dynamically. How does cpu_power of a gorup (which I believe
refers to the group of "hyper-threaded" cores on one physical core)
change while inthe system is in operation ? Is this in support of
hot-swappable CPU's or something ?
To be honest, for my use case, I'd like to just disable the whole
work-stealing stuff (referred to as load-balancing in the kernel).
There seems to be no config option that isolates just the dynamic
load-balancing parts (or is there ?) so maybe I'd just hack away the
load-balancing functions by hand so as never to worry about those
denominators again.
Chetan
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