From: Francis Cianfrocca <garbagecat10@...>
Date: 2006-07-26T21:53:17+09:00
Subject: Re: For performance, write it in C

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One important thing about Ruby performance is that Ruby gets very
inefficient very quickly, as the size of the working set grows. This
manifests as an observed performance problem, but the tip-off is that
performance of a particular Ruby program is quite acceptable for small
data-set sizes (such as in your test fixtures), but falls off a cliff with
production data-sets. Most of the times that I have found myself rewriting
slow Ruby code in C have been to get a program that runs in far less memory,
by manually laying out the data structures. This improves performance not
only for the obvious reasons (less thrashing and less contention with other
processes on a busy server), but also because you can "help" the processor's
cache manager to get more hits by creating localities of reference and by
stuffing more of your working set into a smaller number of cache lines. This
matters all the more on multiprocessors, which are severely penalized by
cache misses, to the point that some naively-written programs can run
noticeably faster on a uniprocessor.

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