Re: [PATCH 11/17] Fully activate the sliding window pack access.

[Linus Torvalds <torvalds@osdl.org>]

On Sat, 23 Dec 2006, Shawn O. Pearce wrote:
>
> This finally turns on the sliding window behavior for packfile data
> access by mapping limited size windows and chaining them under the
> packed_git->windows list.

Hmm. You seem to default the window size to 32MB.

Maybe I'm reading that code wrong, but I think that's a bit sad.

In particular, in any setup that doesn't like mmap() at all (eg Cygwin), 
and uses the "malloc+read" emulation, 32MB is actually likely much too 
big. It's probably better to use something like a 1MB slice instead, since 
otherwise you'll often be reading much too much.

So I'd argue that if you fall back to read() (or pread) instead of mmap, 
the 32MB thing is way too big.

So maybe you should make the default depend on NO_MMAP (although it would 
seem that the default Makefile makes Cygwin actually default to using mmap 
these days, so maybe it's not a big deal).

		Linus