[llvm-dev] [RFC] One or many git repositories?

James Molloy via llvm-dev
2016-07-27T18:32:26Z

David,

While I understand the rationale here, I vote for all or nothing. A middle
ground seems to me to hold none of the advantages and all of the
disadvantages!

James
On Wed, 27 Jul 2016 at 19:30, David Chisnall via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> On 27 Jul 2016, at 19:03, Bruce Hoult via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> >
> > What do you believe is this increased burden?
> >
> > The entire commit history of all llvm projects in a mono-repository is
a
> 449 MB .git directory. It can be downloaded in about two minutes on a
> typical domestic internet connection (50 Mbps).
> >
> > If you download only a snapshot of the current HEAD commit then the
.git
> repository is 88 MB and takes under a minute. Any other individual commit
> should be similar.
> >
> > This doesn't seem like a big burden to me.
> >
> > The checked out llvm source directory -- which you say is all that
many
> people want -- is 202 MB. That's without even building it.
> >
> > Why is this burden unacceptable? It seems rather small to me.
> >
> > For comparison, using svn to checkout llvm using ...
> >
> > svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm
> >
> > ... took me 1 minute 28 seconds and gives a 222 MB .svn directory, 428
> MB total (so 206 MB for the source files checked out).
>
> The burden, as he pointed out, is for people who contribute to
> llvm-umbrella projects that are not llvm.
>
> I think that this is a very good reason for not including libc++ in the
> monorepo.  Currently, it takes me about 15 seconds to do an checkout of
> libc++ and the result is about 100MB.  A clone from the git mirror takes
> just under 6 seconds, downloads 17.15MB, and produces a 72MB directory.
> The build directory is about 7MB.
>
> There is no dependency from libc++ to anything else in LLVM.  In FreeBSD,
> we use libc++ with both clang and gcc and people hacking on libc++ do not
> typically need to build a new toolchain to do so.  Pulling in all of LLVM,
> clang, lldb, lld, and so on just to hack on libc++ seems a bit excessive.
>
> libunwind is similar.  It exposes a public interface that’s ABI compatible
> with two other libraries and is tiny.  We currently have people working on
> it in the process of replacing the libunwind in FreeBSD with the LLVM
> version.  Some of them also hack on other bits of LLVM, but getting the
> entire LLVM repo just to hack on a library that’s 1.6MB of source (1.5
> seconds to do an svn checkout currently) seems a bit excessive.
>
> I don’t think it’s a problem for the larger projects (clang, lldb, lld) to
> be in a combined repo, because the size of any of them is fairly small in
> comparison to the size of LLVM and tiny in comparison to the build
> directory.
>
> David
>
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