> -----Original Message----- > From: Johannes Schindelin [mailto:johannes.schinde...@gmx.de] > Sent: Thursday, April 20, 2017 5:58 PM > To: Jeff King <p...@peff.net> > Cc: David Turner <david.tur...@twosigma.com>; git@vger.kernel.org > Subject: Re: [PATCH] Increase core.packedGitLimit > > Hi Peff, > > 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 > > Documentation/config.txt. > > > > > 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.
We might want to think about replacing git_config_ulong with git_config_size_t in nearly all cases. "long" has ceased to be useful. More modern versions of C prefer uint64_t, but I think that we'll usually want size_t because these values will be used as memory limits of various sorts.
