Some mmap observations compared to Linux 2.6/OpenBSD
Ted Unangst
tedu at stanford.edu
Fri Oct 24 14:12:02 PDT 2003
On Fri, 24 Oct 2003, Michel TALON wrote:
> What is more interesting is to look at the actual benchmark results in
> http://bulk.fefe.de/scalability/
> in particular the section about mmap benchmarks, the only one where
> OpenBSD shines. However as soon as touching pages is benchmarked
> OpenBSD fails very much.
look closer. openbsd's "touch page" times are identical to what you'd
expect a disk access to be. the pages aren't cached, they're read from
disk. so compared to systems that don't read from disk, it looks pretty
bad. a 5 line patch to fix the benchmark so that the file actually is
cached on openbsd results in performance much in line with freebsd/linux.
--
"People have criticized me because my security detail is larger
than the president's. But you must ask yourself: are there more
people who want to kill me than who want to kill the president?
I can assure you there are."
- M. Barry, Mayor of Washington, DC
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