Messages in this thread | | | Subject | Re: A scrub daemon (prezeroing) | From | Nick Piggin <> | Date | Fri, 04 Feb 2005 17:43:23 +1100 |
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On Thu, 2005-02-03 at 22:26 -0800, Christoph Lameter wrote: > On Fri, 4 Feb 2005, Paul Mackerras wrote: > > > As has my scepticism about pre-zeroing actually providing any benefit > > on ppc64. Nevertheless, the only definitive answer is to actually > > measure the performance both ways. > > Of course. The optimization depends on the type of load. If you use a > benchmark that writes to all pages in a page then you will see no benefit > at all. For a kernel compile you will see a slight benefit. For processing > of a sparse matrix (page tables are one example) a significant benefit can > be obtained.
If you have got to the stage of doing "real world" tests, I'd be interested to see results of tests that best highlight the improvements.
I imagine many general purpose server things wouldn't be helped much, because they'll typically have little free memory, and will be continually working and turning things over.
A kernel compile on a newly booted system? Well that is a valid test. It is great that performance doesn't *decrease* in that case :P
Of course HPC things may be a different story. It would be good to see your gross improvement on typical types of workloads that can best leverage this - and not just initial ramp up phases while memory is being faulted in, but the the full run time.
Thanks, Nick
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