Re: scheduling problem?

[Mike Galbraith]

On Wed, 3 Jan 2001, Roger Larsson wrote:

> Hi,
> 
> I have played around with this code previously.
> This is my current understanding.
> [yield problem?]

Hmm.. this ~could be.  I once dove into the VM waters (me=stone)
and changed __alloc_pages() to only yield instead of scheduling.
The results (along with many other strange changes) were.. weirdest
feeling kernel I ever ran.  Damn fast, but very very weird ;-)

> Possible (in -prerelease) untested possibilities.
> 
> * Be tougher when yielding.
> 
> 
>  	wakeup_kswapd(0);
> 	if (gfp_mask & __GFP_WAIT) {
> 		__set_current_state(TASK_RUNNING);
> 		current->policy |= SCHED_YIELD;
> +               current->counter--; /* be faster to let kswapd run */
> or
> +               current->counter = 0; /* too fast? [not tested] */
> 		schedule();
> 	}

That looks a lot like cheating.

> * Move wakeup of bflushd to kswapd. Somewhere after 'do_try_to_free_pages(..)'
>   has been run. Before going to sleep... 
>   [a variant tested with mixed results - this is likely a better one]

I also did some things along this line.. also with mixed results.

:) the changes I've done that I actually like best is to kill bdflush
graveyard dead.  Did that twice and didn't miss it at all.  (next time,
I think I'll erect a headstone)

	-Mike