Re: Cygwin can't handle huge packfiles?

From: Christopher Faylor <me@cgf.cx>
Date: Apr 5, 2006, 21:08 UTC
Message-ID: <20060405210844.GN26780@trixie.casa.cgf.cx>
In-Reply-To: <Pine.LNX.4.63.0604051612200.25304@wbgn013.biozentrum.uni-wuerzburg.de>

On Wed, Apr 05, 2006 at 04:14:20PM +0200, Johannes Schindelin wrote:

Show 11 quoted lines

>> Inspired by a patch of Alex Riesen (thanks, Alex), I tried to use the
>> regular mmap for mapping pack files, only to discover that I compile
>> without defining "NO_MMAP", so I've been using the stock mmap all
>> along. So now I'm thinking that the cygwin mmap also does a
>> malloc-and-read, just like git does with NO_MMAP. So I'll continue to
>> investigate in that direction.
>
>I think cygwin's mmap() is based on the Win32 API equivalent, which could 
>mean that it *is* memory mapped, but in a special area (which is smaller 
>than 1.5 gigabyte). In this case, it would make sense to limit the pack 
>size, thereby having several packs, and mmap() them as they are needed.

Yes, cygwin's mmap uses CreateFileMapping and MapViewOfFile. IIRC, Windows might have a 2G limitation lurking under the hood somewhere but I think that might be tweakable with some registry setting.

cgf