Messages in this thread | | | Date | Tue, 15 Jan 2008 12:20:10 +0900 | From | KOSAKI Motohiro <> | Subject | Re: [RFC] mmaped copy too slow? |
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Hi Rik
> While being able to deal with used-once mappings in page reclaim > could be a good idea, this would require us to be able to determine > the difference between a page that was accessed once since it was > faulted in and a page that got accessed several times.
it makes sense that read ahead hit assume used-once mapping, may be. I will try it.
(may be, i can repost soon)
> Given that page faults have overhead too, it does not surprise me > that read+write is faster than mmap+memcpy. > > In threaded applications, page fault overhead will be worse still, > since the TLBs need to be synchronized between CPUs (at least at > reclaim time).
sure. but current is unnecessary large performance difference. I hope improvement it because copy by mmapd is very common operation.
> Maybe we should just advise people to use read+write, since it is > faster than mmap+memcpy?
Time is solved to it :) thanks!
- kosaki
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