Re: Very long startup time for a new thread

[Mike Galbraith <efault@gmx.de>]

On Thu, 2006-07-13 at 08:07 +0200, Mikael Starvik wrote:
> (This is on a 200 MIPS embedded architecture).
> 
> On a heavily loaded system (loadavg ~4) I create a new pthread. In this
> situation it takes ~4 seconds (!) before the thread is first scheduled in
> (yes, I have debug outputs in the scheduler to check that). In a 2.4 based
> system I don't see the same thing. I don't have any RT or FIFO tasks. Any
> ideas why it takes so long time and what I can do about it?

If your new thread is runnable but not selected for those ~4 seconds, it
could be the interactivity code.  Try disabling that.

If you want to try a patch that targets this area, I have an old one for
2.6.16 you can play with.  With it, you can pretty much disable the
interactivity code without losing dynamic priority adjustment.  I also
have one for 2.6.17, and that one removes the interactivity code
entirely (hmm) but it also actively intervenes in scheduling decisions,
so might not be a good diagnostic.

	-Mike