Re: [PATCH] use local_t for page statistics

[Nick Piggin]

Andi Kleen wrote:
> On Saturday 07 January 2006 03:52, Nick Piggin wrote:
>
>
> > No. On many load/store architectures there is no good way to do local_t,
> > so something like ppc32 or ia64 just uses all atomic operations for
>
>
> well, they're just broken and need to be fixed to not do that.

How?

> Also I bet with some tricks a seqlock like setup could be made to work.

I asked you how before. If you can come up with a way then it indeed
might be a good solution... The problem I see with seqlock is that it
is only fast in the read path. That path is not the issue here.

> > local_t, and ppc64 uses 3 counters per-cpu thus tripling the cache
> > footprint.
>
>
> and ppc64 has big caches so this also shouldn't be a problem.

Well it is even less of a problem for them now, by about 1/3.

Performance-wise there is really no benefit for even i386 or x86-64
to move to local_t now either so I don't see what the fuss is about.

--
SUSE Labs, Novell Inc.

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