On Jul 29, 2005, at 9:07 AM, Elliott Hughes wrote:
i don't have much experience of MS Windows, but compared to Linux,
Mac OS' file I/O blows goats. it doesn't seem to be Java's fault:
it's the OS itself.
one thing that's particularly crippling is Mac OS' apparent lack
of interest in caching data (meta and user, from what i remember,
but definitely user). Linux really goes all-out to cache as much
as it can for as long as it can, and it really pays off on
successive reads. Mac OS doesn't get much faster, no matter how
many times you read something.
you can observe this with grep(1) or whatever. grep the GCC source
tree, say, on Linux and Mac OS machines with lots of memory. gasp
in awe at the Linux machine's second run, and maybe throw a party
for it to give the Mac chance to catch up.
Mac OS X uses file caching pervasively and successfully. I have
done tests with files on the order a few GB in size on my system
with 4 GB of RAM when I was developing fibre channel drivers for
Mac OS X. Secondary reading of the data happens from RAM not disk
in my testing. In other words I have found the Mac OS X has what
you think it lacks (far back as 10.1 in my testing if not earlier).
i'm not claiming it's lacking. i'm claiming it isn't very good.
my statement "Mac OS doesn't get much faster, no matter how many
times you read something" was inaccurate. what i meant was "for the
kind of test i'm talking about, involving lots of metadata and lots
of userdata, Mac OS does get faster on the second run, but not to the
same extent as Linux, on which successive runs are effectively free".
example numbers would be 23s (cold) versus 7s (cached) on Mac OS,
compared to 20s (cold) versus 0s (cached) on Linux.
try the real-world "grep GCC" test i mention, rather than these
artificial single-file microbenchmarks people have started posting.
(the original poster, like me, was interested in lots of fairly small
files.)
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