Scheduler balancing statistics

[Nick Piggin]

Hi,
I have been adapting Rick's schedstats package to extract
more information from the sched-domains infrastructure.

Before I release a patch, I'd like some input as to what
statistics people want covered, and in what form they would
like them presented (I'm talking only about balancing).

I have covered the basic stuff I could think of, and
written a small C program to parse it (I'm no good at perl)
and output this (sorry it is still pretty ugly):

npiggin@didi:~/usr/src/linux-2.4$ stats7 pre post
For domain0
 31.005358l load balance calls / s move 1.162474l tasks / s
  Of which, 66.198008l% calls and 67.187500l% task moves from idle balancing
   93.539823l% found no imbalance
   2.654867l% found an imbalance but failed
   30.232558l% of tasks were moved with cache nice
  Of which, 25.834798l% calls and 28.125000l% task moves from busy balancing
   95.918367l% found no imbalance
   0.000000l% found an imbalance but failed
   100.000000l% of tasks were moved with cache nice
  Of which, 7.967194l% calls and 4.687500l% task moves from newidle balancing
   94.117647l% found no imbalance
   0.000000l% found an imbalance but failed
   100.000000l% of tasks were moved with cache nice
 0.000000l active balances / s  move 0.000000l tasks / s
 0.036327l passive load balances / s
 2.070657l affine wakeups / s
 0.000000l exec balances / s

This was the behaviour during a make -j4 bzImage on a 2xSMP. For
a NUMA system, it would also give you domain1 for example.

A few interesting things this tells us: load_balance is being
called 31 times per second, ~95% of the time there is no imbalance,
and it moves 1.16 tasks per second.

idle balancing is going over the cache_nice_tries limit 70% of
the time which might warrant cache_nice_tries being increased.

etc.

Comments?
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