Cached file read performance
davidxu at freebsd.org
Thu Dec 21 18:08:10 PST 2006
Mark Kirkwood wrote:
> I recently did some testing on the performance of cached reads using two
> (almost identical) systems, one running FreeBSD 6.2PRE and the other
> running Gentoo Linux - the latter acting as a control. I initially
> started a thread of the same name on -stable, but it was suggested I
> submit a mail here.
> My background for wanting to examine this is that I work with developing
> database software (postgres internals related) and cached read
> performance is pretty important - since we typically try hard to
> encourage cached access whenever possible.
> Anyway on to the results: I used the attached program to read a cached
> 781MB file sequentially and randomly with a specified block size (see
> below). The conclusion I came to was that our (i.e FreeBSD) cached read
> performance (particularly for smaller block sizes) could perhaps be
> improved... now I'm happy to help in any way - the machine I've got
> running STABLE can be upgraded to CURRENT in order to try out patches
> (or in fact to see if CURRENT is faster at this already!)...
> Best wishes
I suspect in such a test, memory copying speed will be a key factor,
I don't have number to back up my idea, but I think Linux has lots
of tweaks, such as using MMX instruction to copy data.
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