Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH 4/3] Replace dynamic percpu implementation | Date | Fri, 23 May 2003 09:56:01 +1000 |
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In message <20030522104944.GE27614@in.ibm.com> you write: > On Thu, May 22, 2003 at 06:36:31PM +1000, Rusty Russell wrote: > > Interesting: personally I consider the cacheline sharing a feature, > > and unless you've done something special, the static declaration > > should be interlaced too, no? > > Yes, the static declartion was interlaced too. What I meant to say is that > cacheline sharing feature helped alloc_percpu/static percpu, compensate > for the small extra memory reference cost in getting __percpu_offset[] > when you compare with kmalloc_percpu_new.
Ah, thanks, that clarifies. Sorry for my misread.
> > Aside: if kmalloc_percpu uses the per-cpu offset too, it probably > > makes sense to make the per-cpu offset to a first class citizen, and > > smp_processor_id to be derived, rather than the other way around as at > > the moment. This would offer further speedup by removing a level of > > indirection. > > > > If you're interested I can probably produce such a patch for x86... > > Sure, it might help per-cpu data but will it cause performance > regression elsewhere? (other users of smp_processor_id).
AFAICT, all the time-critical smp_processor_id() things are basically for indexing into a per-cpu data array. Even things like module.h and percpu_counter.h would benifit from replacing those huge inside-structure [NR_CPUS] arrays with a dynamic allocation.
> I can run it through the same tests and find out. Maybe it'll make > good paper material for later? ;)
I'll try to find time today or early next week.
Thanks! Rusty. -- Anyone who quotes me in their sig is an idiot. -- Rusty Russell. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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