Re: bad lmbench numbers for mmap

David Miller (davem@twiddle.net)
Fri, 16 Apr 1999 23:54:08 -0700


From: torvalds@transmeta.com (Linus Torvalds)
Date: 17 Apr 1999 06:28:46 GMT

I don't see that this problem should be anything new. Have we ever
been any good at lat_mmap? I don't think so..

It may be that in a previous version of lat_mmap it did only read
taps, but Larry for one reason or another changed those into writes.

Does anyone have any of the older lmbench beta's around? Say from
about 8 to 12 months ago or so? This would help me check my sanity.

I do agree that doing writes is probably not making the benchmark
report what the name would indicate. However I do see that a version
that does writes is useful (think of a linker implementation that
mmap's the final object file it creates, or some mmap'd database of
some sort). But such a benchmark should have a different name
(lat_mmapwrite, or somesuch).

Later,
David S. Miller
davem@redhat.com

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