Re: [PATCH] Increase core.packedGitLimit
- Date: Thu, 20 Apr 2017 23:58:14 +0200 (CEST)
- From: Johannes Schindelin <Johannes.Schindelin@xxxxxx>
- Subject: Re: [PATCH] Increase core.packedGitLimit
On Thu, 20 Apr 2017, Jeff King wrote:
> On Thu, Apr 20, 2017 at 04:41:18PM -0400, David Turner wrote:
> > When core.packedGitLimit is exceeded, git will close packs. If there
> > is a repack operation going on in parallel with a fetch, the fetch
> > might open a pack, and then be forced to close it due to
> > packedGitLimit being hit. The repack could then delete the pack
> > out from under the fetch, causing the fetch to fail.
> > Increase core.packedGitLimit's default value to prevent
> > this.
> > On current 64-bit x86_64 machines, 48 bits of address space are
> > available. It appears that 64-bit ARM machines have no standard
> > amount of address space (that is, it varies by manufacturer), and IA64
> > and POWER machines have the full 64 bits. So 48 bits is the only
> > limit that we can reasonably care about. We reserve a few bits of the
> > 48-bit address space for the kernel's use (this is not strictly
> > necessary, but it's better to be safe), and use up to the remaining
> > 45. No git repository will be anywhere near this large any time soon,
> > so this should prevent the failure.
> Yep, I think this is a reasonable direction.
> > ---
> > git-compat-util.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> This probably needs an update to the core.packedGitLimit section of
> > diff --git a/git-compat-util.h b/git-compat-util.h
> > index 8a4a3f85e7..1c5de153a5 100644
> > --- a/git-compat-util.h
> > +++ b/git-compat-util.h
> > @@ -616,7 +616,7 @@ extern int git_lstat(const char *, struct stat *);
> > #endif
> > #define DEFAULT_PACKED_GIT_LIMIT \
> > - ((1024L * 1024L) * (size_t)(sizeof(void*) >= 8 ? 8192 : 256))
> > + ((1024L * 1024L) * (size_t)(sizeof(void*) >= 8 ? (32 * 1024L * 1024L) : 256))
> I wondered if we would run afoul of integer sizes on 64-bit systems where
> "long" is still only 32-bits (i.e., Windows). But I think it's OK,
> because the values before we cast to size_t are in megabytes. So your
> 32*1024*1024 needs only 25 bits to store it. And then after we cast to
> size_t, everything is in 64-bit.
Indeed, when I patch a local Git checkout accordingly, I see that
packed_git_limit is set to 35184372088832.
The bigger problem in this regard is that users are allowed to override
this via core.packedgitlimit but that value is parsed as an unsigned long.