Re: -mm merge plans for 2.6.20

[Nick Piggin]

Paul Mackerras wrote:
> Andrew Morton writes:

> > radix-tree-rcu-lockless-readside.patch
> >
> > There's no reason to merge this yet.
>
>
> We want to use it in some powerpc arch code.  Currently we use a
> per-cpu array of spinlocks, and this patch would let us get rid of
> that array.

I'd like to get another patch in here before going upstream if possible.
It is not a correctness fix, but it is a bit of a rework.

I also wouldn't mind getting the readahead path, if not the full
pagecache readside, out from under tree_lock in -mm kernels to exercise
the radix-tree concurrency a bit more.

It's just been painfully slow, recently because of these more important
buffered write vs deadlock and pagefault vs invalidate problems that
I've been working on. I don't feel I can load up -mm with too much
unrelated stuff that messes with mm/pagecache internals.

I guess the per-cpu spinlocks are pretty reasonable for scalability,
and you are mainly looking to eliminate the lock/unlock cost in your
interrupt path?

Nick

--
SUSE Labs, Novell Inc.
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