Re: [PATCH] self tuning scheduler

[Mike Galbraith]

Greetings,

I took your patch out for a test-drive, and it appears to have starvation 
problems with irman's process load (dang thing seems to be HELL on schedulers).

Irman starts a load (defaults to 9 tasks passing data in a pipe ring), and 
forks a child which pingpongs one character back and forth to the parent 
for 1000000 iterations, measuring response time for each iteration and 
computing statistics.  With an iteration % 1000 printf() in the evaluation 
routine, I see it start off nice and fast, then begins to get starved for 
up to 30 seconds.  It jerks around for a bit, then slows down to a ~stable 
1 sec/iteration after approximately 300000 iterations.  The whole test 
takes ~2minutes with 2.5.64-virgin.  (I'm not patient enough to wait for 
the rest of the .5million iterations left on this burn before reporting:)

It also shows a serious throughput loss with make -j30 bzImage on this box 
(I think you expect that though from what I read).  With stock, it takes 
~8m30s... this scheduler adds a full minute.

The window wave test with a make -j5 bzImage running (fits easily in ram) 
is pretty ragged.

Ending on a more positive note, vmstat output from the parallel build looks 
quite nice.

	-Mike