git@vger.kernel.org mailing list mirror (one of many)
 help / Atom feed
From: David Turner <David.Turner@twosigma.com>
To: 'Johannes Schindelin' <Johannes.Schindelin@gmx.de>,
	Jeff King <peff@peff.net>
Cc: "git@vger.kernel.org" <git@vger.kernel.org>
Subject: RE: [PATCH] Increase core.packedGitLimit
Date: Thu, 20 Apr 2017 22:04:36 +0000
Message-ID: <4c111acb3f134aa9aef8648d75bd741f@exmbdft7.ad.twosigma.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1704202355230.3480@virtualbox>


> -----Original Message-----
> From: Johannes Schindelin [mailto:Johannes.Schindelin@gmx.de]
> Sent: Thursday, April 20, 2017 5:58 PM
> To: Jeff King <peff@peff.net>
> Cc: David Turner <David.Turner@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.


  reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-20 20:41 David Turner
2017-04-20 21:02 ` Jeff King
2017-04-20 21:58   ` Johannes Schindelin
2017-04-20 22:04     ` David Turner [this message]
2017-04-21  9:34       ` Johannes Schindelin
2017-06-21 13:51   ` [PATCH] docs: update 64-bit core.packedGitLimit default Jeff King
2017-06-21 16:25     ` Stefan Beller
2017-06-21 18:06       ` Jeff King
2017-06-21 18:38         ` Junio C Hamano
2017-06-21 18:53           ` Jeff King
2017-06-21 19:22             ` Junio C Hamano
2017-06-21 19:31               ` Jeff King
2017-06-21 13:44 ` [PATCH] Increase core.packedGitLimit Jeff King

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://vger.kernel.org/majordomo-info.html

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=4c111acb3f134aa9aef8648d75bd741f@exmbdft7.ad.twosigma.com \
    --to=david.turner@twosigma.com \
    --cc=Johannes.Schindelin@gmx.de \
    --cc=git@vger.kernel.org \
    --cc=peff@peff.net \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

git@vger.kernel.org mailing list mirror (one of many)

Archives are clonable:
	git clone --mirror https://public-inbox.org/git
	git clone --mirror http://ou63pmih66umazou.onion/git
	git clone --mirror http://czquwvybam4bgbro.onion/git
	git clone --mirror http://hjrcffqmbrq6wope.onion/git

Newsgroups are available over NNTP:
	nntp://news.public-inbox.org/inbox.comp.version-control.git
	nntp://ou63pmih66umazou.onion/inbox.comp.version-control.git
	nntp://czquwvybam4bgbro.onion/inbox.comp.version-control.git
	nntp://hjrcffqmbrq6wope.onion/inbox.comp.version-control.git
	nntp://news.gmane.org/gmane.comp.version-control.git

 note: .onion URLs require Tor: https://www.torproject.org/
       or Tor2web: https://www.tor2web.org/

AGPL code for this site: git clone https://public-inbox.org/ public-inbox