Messages in this thread | | | Date | Sun, 31 Oct 2004 00:45:28 +0200 | From | Andrea Arcangeli <> | Subject | Re: PG_zero |
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On Sat, Oct 30, 2004 at 02:07:32PM -0700, Andrew Morton wrote: > I wonder if it would help if the page zeroing in the idle thread was done > with the CPU cache disabled. It should be pretty easy to test - isn't it > just a matter of setting the cache-disable bit in the kmap_atomic() > operation?
it's certainly an improvement I agree, however I don't measure a slowdown here, so I'm not sure if it will make any significant difference either. Plus the idle clearing code in theory could be disabled and what would remain after that shall be an improvement over current code.
I share your concern on the fact there seems not to be any speedup in my 2-way boxes unless I microbenchmark (but if I microbenchmark the best case the speedup is very huge). OTOH the same applies to the per-cpu queues at large, they only are measurable on the big boxes. Overall if we've to use slab for the pte just to cache zero (which for sure won't be a measurable speedup either in any small box using a _macro_ benchmark), this looks better design IMHO since it boosts everything zero related, not just the pte. Plus it fixes some mistake in the current code (like the failure of utilizing properly all the quicklists belonging to each classzone [current code falls back into the buddy before falling back in the lower zone quicklist] and the waste of resouces in keeping the hot and cold caches separated, and the no point for low watermark in the quicklists and other very minor details).
> There are quite a few patches happening in this area - the > make-kswapd-aware-of-higher-order-pages patches and the no-buddy-bitmap > patches are queued in -mm. It'll take some time to work through them > all...
Sure take your time (and this is only an experiment so far anyways). Only I'll do the reject fixup after they're in mainline so I've less chance of doing useless rediff work. - 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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