From: Francis Cianfrocca <garbagecat10@...>
Date: 2006-08-13T23:31:02+09:00
Subject: Re: Looking for a Fast Persistent Store

On 8/13/06, Bob Hutchison <hutch@recursive.ca> wrote:
> something wrong in my testing... silly benchmarks forthcoming). In
> Java, Perst is *much* faster than the filesystem.
>

Ok, did some reading up on Perst- no real magic there. They simply put
together a lot of the good techniques you would expect to find in a
virtual arena manager, and they made some guesses about the handful of
tough questions you have to answer. (Allocation-grain size, page size,
etc.) I used same kind of bitmap-strategy for the persistent
GD-message system I mentioned upthread, but Perst makes a different
choice: they sequentially search the bitmap pages for a big-enough
free space when storing an object. Even though they use the obvious
optimization (storing a max-available-size on each page), I remember
being phobic about that approach and did something much more elaborate
(but reliably O(1)). But given your comments about Perst's speed, they
have obviously made the right choices overall!

I think something like Perst could be done in Ruby, possibly augmented
with a tiny C extension to access virtual-memory features.