[Sugar-devel] poor man's mmap "sliding window" on Python 2.5.x

Benjamin M. Schwartz bmschwar at fas.harvard.edu
Mon Jul 6 12:06:52 EDT 2009

Martin Langhoff wrote:
> Along the way, found that Python 2.5.x doesn't support an offset to
> mmap(), which at first blush makes re-mapping with a sliding window
> problematic.

Why is an explicit sliding window necessary?  Isn't the point of mmap that
you can access as you like, and the kernel will clear old caches if
there's memory pressure?

> On the XO-1, it's the difference of "churning through it" and slowing
> the whole OS to a crawl, and then inching towards a big OOM zap.

Is this (a) a kernel bug, (b) Python layering extra caching over mmap, or
(c) a misunderstanding of mmap on my part?


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