Re: Problem with large files on different OSes

On May 27, 2009, at 12:52 PM, Christopher Jefferson wrote:

I recently came across a very annoying problem, characterised by the  
following example:

On a recent ubuntu install:

dd if=/dev/zero of=file bs=1300k count=1k
git commit file -m "Add huge file"


The repository can be pulled and pushed successfully to other ubuntu  
installs, but on Mac OS X, 10.5.7 machine with 4GB ram git pull  
produces:

remote: Counting objects: 6, done.
remote: git(1533,0xb0081000) malloc: *** mmap(size=1363152896)  
failed (error code=12)
remote: *** error: can't allocate region
remote: *** set a breakpoint in malloc_error_break to debug
remote: git(1533,0xb0081000) malloc: *** mmap(size=1363152896)  
failed (error code=12)
remote: *** error: can't allocate region
remote: *** set a breakpoint in malloc_error_break to debug
remote: fatal: Out of memory, malloc failed
error: git upload-pack: git-pack-objects died with error.
fatal: git upload-pack: aborting due to possible repository  
corruption on the remote side.
remote: aborting due to possible repository corruption on the remote  
side.
fatal: protocol error: bad pack header


The problem appears to be the different maximum mmap sizes available  
on different OSes. Whic I don't really mind the maximum file size  
restriction git imposes, this restriction varying from OS to OS is  
very annoying, fixing this required rewriting history to remove the  
commit, which caused problems as the commit had already been pulled,  
and built on, by a number of developers.

If the requirement that all files can be mmapped cannot be easily  
removed, would be it perhaps be acceptable to impose a (soft?)  
1GB(ish) file size limit? I suggest 1GB as all the OSes I can get  
hold of easily (freeBSD, windows, Mac OS X, linux) support a mmap of  
size > 1GB.

I think this is a limitation of a 32bit build of git. I just tried  
with a 64bit build and it added the file just fine. The compiler on  
MacOSX (gcc) produces 32bit builds by default, even if the system  
supports 64bit executables. But gcc on 64bit Linux (at least the  
installations I have at home) produces a 64bit executables by default.  
Solaris/OpenSolaris behaves like MacOSX, no idea about *BSD or  
Windows. Maybe this is why git works on Linux but not MacOSX even on  
the same hardware.
Btw, I built git with: make install prefix=... CC="gcc -m64", no  
modifications needed (MacOSX 10.5.7).

tom