Re: must-fix list for 2.6.0

[Andrew Morton]

[e-mail] wrote:
>
> On Wed, Apr 30, 2003 at 04:21:08PM -0700, Andrew Morton wrote:
> > menu if there was a kernel build happening at the same time.  That is just
> > utterly broken, so if we're going to leave the sched.c code as-is then we
> > *require* that all applications be updated to not spin on sched_yield.
> 
> Excuse me, but WTF do they spin on the sched_yield() in the first place?
> _That_ sounds like utterly broken...

I think it's happening down inside the old linuxthreads library.  No idea
who, what, where or why.

There are quite a few places in the kernel which do it, too.  Usually when
waiting for memory to come free.  These are being gradually removed, in
favour of blk_congestion_wait() calls.

That leaves behind the very performance-critical sched_yield() in ext3
transaction batching.  That was designed to allow other processes to join a
transaction before the calling one closes the transaction.  With the new
yield() it was causing horrid starvation and was lamely replaced with a
schedule().  It needs to be resurrected for real, but I'm not sure how. 
Probably just a sleep(0.01).