[webkit-dev] Tip: Use 64-bit git binaries on Mac OS X

Evan Martin evan at chromium.org
Tue Dec 7 16:26:47 PST 2010

It seems from the bug Mihai linked to that the Git+OS X maintainer
thought the only benefit of a 64-bit binary was being able to handle
larger files, but in fact the real benefit is that the increased
address space of a 64-bit binary lets you mmap larger regions.  So it
seems reasonable you could convince the maintainer.

But really, large mmap regions is mostly working around the fact that
Mihai was experiencing mmap taking 40ms.  Git Master Shawn Pearce said
to me: "Try compiling Git with make NO_MMAP=1 and tell me how you like
it. Git comes with a "replacement" mmap() implementation that does
malloc()+read(). This was primarily meant for Win32 cases, but might
be useful on Mac OS X."  In the old thread on the Git list about OS X
performance that Mihai linked to in his blog post, Linus Torvalds
seemed to indicate that he only expected mmap to have performance
comparable to read on Linux, not on other platforms.

So I'd maybe suggest trying that as well and then telling the Git+OS X
maintainer which combination of settings is the best.  :)

On Tue, Dec 7, 2010 at 4:14 PM, Eric Seidel <eric at webkit.org> wrote:
> Can we evangelize the code.google.com project?
> On Dec 7, 2010 4:04 PM, "Mihai Parparita" <mihaip at chromium.org> wrote:
>> After complaining to a Linux-using friend for the n-th time that "git
>> status" was much slower on my Snow Leopard machine than on his Linux
>> box, I decided to look into why this is. As it turns out, most people
>> get git binaries from http://code.google.com/p/git-osx-installer/,
>> which are 32-bit. Switching to 64-bit binaries made git status go from
>> 6.58s to 2.50s (mainly because this does fewer mmaps).
>> You can download a 64-bit binary installer from
>> https://github.com/downloads/mihaip/git_osx_installer/git-,
>> or you can build it yourself (more details at
>> http://blog.persistent.info/2010/12/making-git-faster-on-large-repositories.html).
>> Mihai
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