Re: [RFC] NUMA futex hashing

[Nick Piggin]

Eric Dumazet wrote:

> On Tuesday 08 August 2006 18:34, Nick Piggin wrote:
>
> > Eric Dumazet wrote:
> >
> > > We certainly can. But if you insist of using mmap sem at all, then we
> > > have a problem.
> > >
> > > rbtree would not reduce cacheline bouncing, so :
> > >
> > > We could use a hashtable (allocated on demand) of size N, N depending on
> > > NR_CPUS for example. each chain protected by a private spinlock. If N is
> > > well chosen, we might reduce lock cacheline bouncing. (different threads
> > > fighting on different private futexes would have a good chance to get
> > > different cachelines in this hashtable)
> > See other mail. We already have a hash table ;)
>
> Yes but still you want at FUTEX_WAIT time to tell the kernel the futex is 
> private to this process.

Yes, but I'm saying we already have a hash table. The hash table.

I'm *not* saying you *don't* also want a private directive from userspace.
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