Messages in this thread | | | Date | Fri, 24 Dec 2004 10:21:24 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: Prezeroing V2 [0/3]: Why and When it works |
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On Fri, 24 Dec 2004, Arjan van de Ven wrote: > > problem is.. will it buy you anything if you use the page again > anyway... since such pages will be cold cached now. So for sure some of > it is only shifting latency from kernel side to userspace side, but > readprofile doesn't measure the later so it *looks* better...
Absolutely. I would want to see some real benchmarks before we do this. Not just some microbenchmark of "how many page faults can we take without _using_ the page at all".
I agree 100% with you that we shouldn't shift the costs around. Having a hice hot-spot that we know about is a good thing, and it means that performance profiles show what the time is really spent on. Often getting rid of the hotspot just smears out the work over a wider area, making other optimizations (like trying to make the memory footprint _smaller_ and removing the work entirely that way) totally impossible because now the performance profile just has a constant background noise and you can't tell what the real problem is.
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