Neil Brown <neilb@cse.unsw.edu.au> wrote:
>
> On Thursday January 15, akpm@osdl.org wrote:
> > NeilBrown <neilb@cse.unsw.edu.au> wrote:
> > >
> > > + if (sh == NULL) {
> > > + sh = get_active_stripe(conf, sector_nr, pd_idx, 0);
> > > + /* make sure we don't swamp the stripe cache if someone else
> > > + * is trying to get access
> > > + */
> > > + yield();
> > > + }
> >
> > In 2.6, yield() has utterly awful behaviour when there are a lot of other
> > runnable tasks.
> >
> > Have you tested this when the kernel is busy doing other stuff, like a
> > `make -j2' or a few busywait loops? You might find that rebuild simply
> > stops.
> >
>
> No I haven't, and I'm not near my test box today, so it would be
> awkward.
OK. We had a yeild like that in ext3 for a while. The CPU scheduler
changes killed it stone dead. I ended up just making it a schedule(),
which is too weak and probably broke the transaction batching speedup :(
> No other patches are dependant on that one so you can just leave it
> out if you like.
OK. It'll take a few days after Linus gets back from .au to get all this
stuff flushed out anyway. I'll probably have >700 patches by then.
> I just want to wait until every other runnable process has had a
> turn. Maybe cond_resched() would be better?? I try some things out.
There isn't an equivalent, really. We could add one to the CPU scheduler.
With HZ=1000 you'll probably find that a brief schedule_timeout() is OK.
blk_congestion_wait() probably does the wrong thing too.
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