Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [PATCH] use local_t for page statistics | Date | Sat, 7 Jan 2006 04:25:24 +0100 |
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On Saturday 07 January 2006 04:19, Nick Piggin wrote: > 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?
If anything use the 3x duplicated data setup, not atomic operations.
> > > 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...
I'll try to work something up.
> The problem I see with seqlock is that it > is only fast in the read path. That path is not the issue here.
The common case - not getting interrupted would be fast.
> > > >>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.
Actually P4 doesn't like CLI/STI. For AMD and P-M it's not that much an issue, but NetBurst really doesn't like it.
-Andi
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