Re: [CFT][RFC] HT scheduler

[Nick Piggin]

William Lee Irwin III wrote:

> William Lee Irwin III wrote:
>
> > > It will get contention anyway if they're all pounding on the same futex.
> > > OTOH, if they're all threads in the same process, they can hit other
> > > problems. I'll try to find out more about hackbench.
>
>
> On Fri, Dec 12, 2003 at 12:30:07AM +1100, Nick Piggin wrote:
>
> > Oh, sorry I was talking about volanomark. hackbench AFAIK doesn't use
> > futexes at all, just pipes, and is not threaded at all, so it looks like
> > a different problem to the volanomark one.
> > hackbench runs into trouble at large numbers of tasks too though.
>
> Volano is all one process address space so it could be ->page_table_lock;
> any chance you could find which spin_lock() call the pounded chunk of the
> lock section jumps back to?

OK its in futex_wait, up_read(&current->mm->mmap_sem) right after
out_release_sem (line 517).

So you get half points. Looks like its waiting on the bus rather than
spinning on a lock. Or am I'm wrong?


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