On Wed, Oct 10 2018, Ævar Arnfjörð Bjarmason wrote: > On Wed, Oct 10 2018, Martin Langhoff wrote: > >> Looking around, Jonathan Tan's "[PATCH] gc: do not warn about too many >> loose objects" makes sense to me. >> >> - remove unactionable warning >> - as the warning is gone, no gc.log is produced >> - subsequent gc runs don't exit due to gc.log >> >> My very humble +1 on that. >> >> As for downsides... if we have truly tons of _recent_ loose objects, >> it'll ... take disk space? I'm fine with that. > > As Jeff's > https://public-inbox.org/git/20180716175103.GB18636@xxxxxxxxxxxxxxxxxxxxx/ > and my https://public-inbox.org/git/878t69dgvx.fsf@xxxxxxxxxxxxxxxxxxx/ > note it's a bit more complex than that. > > I.e.: > > - The warning is actionable, you can decide to up your expiration > policy. > > - We use this warning as a proxy for "let's not run for a day", > otherwise we'll just grind on gc --auto trying to consolidate > possibly many hundreds of K of loose objects only to find none of > them can be pruned because the run into the expiry policy. With the > warning we retry that once per day, which sucks less. > > - This conflation of the user-visible warning and the policy is an > emergent effect of how the different gc pieces interact, which as I > note in the linked thread(s) sucks. > > But we can't just yank one piece away (as Jonathan's patch does) > without throwing the baby out with the bathwater. > > It will mean that e.g. if you have 10k loose objects in your git.git, > and created them just now, that every time you run anything that runs > "gc --auto" we'll fork to the background, peg a core at 100% CPU for > 2-3 minutes or whatever it is, only do get nowhere and do the same > thing again in ~3 minutes when you run your next command. > > - I think you may be underestimating some of the cases where this ends > up taking a huge amount of disk space (and now we'll issue at least > *some*) warning. See my > https://public-inbox.org/git/87fu6bmr0j.fsf@xxxxxxxxxxxxxxxxxxx/ > where a repo's .git went from 2.5G to 30G due to being stuck in this > mode. > >> For more aggressive gc options, thoughts: >> >> - Do we always consider git gc --prune=now "safe" in a "won't delete >> stuff the user is likely to want" sense? For example -- are the >> references from reflogs enough safety? > > The --prune=now command is not generally safe for the reasons noted in > the "NOTES" section in "git help gc". > >> - Even if we don't, for some commands it should be safe to run git gc >> --prune=now at the end of the process, for example an import that >> generates a new git repo (git svn clone). > > Yeah I don't see a problem with that, I didn't know about this > interesting use-case, i.e. that "git svn clone" will create a lot of > loose objects. > > As seen in my > https://public-inbox.org/git/87tvm3go42.fsf@xxxxxxxxxxxxxxxxxxx/ I'm > working on making "gc --auto" run at the end of clone for unrelated > reasons, i.e. so we generate the commit-graph, seems like "git svn > clone" could do something similar. > > So it's creating a lot of garbage during its cloning process that can > just be immediately thrown away? What is it doing? Using the object > store as a scratch pad for its own temporary state? To answer my own question (which was based on a thinko) it's continually creating loose objects during import, i.e. packs are not involved (don't know why I thought that), so yeah, because all of those have <2wks expiry we end up warning as gc --auto is run. But I actually think the git-svn import is revealing an entirely different problem. I.e. when I clone I seem to be getting a refs/remotes/git-svn branch that's kept up-to-date, and when I "gc" everything's consolidated into a pack, we don't have any loose objects that are meant for expiry. But the reason git-svn is whining is because we're doing this in gc (simplified for the sake af discussion): if (too_many_loose()) { expire(); repack(); if (too_many_loose()) die("oh noes too many loose that don't match our expiry policy!"); } But they don't fall under our expiry policy at all, we're just assuming that a crapload of loose objects haven't been added in the interim from when we ran expire() + repack() until when we check too_many_loose() again. That's a logic error which we could just solve at some expense by seeing *which* objects are loose and candidates for expiry at the beginning, and not warning if at the end we have *different* loose objects that should be consolidated, that just means we genuinely should run gc again. Or is this just wrong? I don't really know. If the above is true I'm missing how tweaking gc.pruneExpire=5.minutes.ago is helping. Surely we'd either just end up with the same set of loose objects (since the clone is still running), or alternatively if git-svn hadn't gotten around to updating refs create a corrupt repo. >> m >> On Tue, Oct 9, 2018 at 10:49 PM Junio C Hamano <gitster@xxxxxxxxx> wrote: >>> >>> Forwarding to Jonathan, as I think this is an interesting supporting >>> vote for the topic that we were stuck on. >>> >>> Eric Wong <e@xxxxxxxxx> writes: >>> >>> > Martin Langhoff <martin.langhoff@xxxxxxxxx> wrote: >>> >> Hi folks, >>> >> >>> >> Long time no see! Importing a 3GB (~25K revs, tons of files) SVN repo >>> >> I hit the gc error: >>> >> >>> >> warning: There are too many unreachable loose objects; run 'git prune' >>> >> to remove them. >>> >> gc --auto: command returned error: 255 >>> > >>> > GC can be annoying when that happens... For git-svn, perhaps >>> > this can be appropriate to at least allow the import to continue: >>> > >>> > diff --git a/perl/Git/SVN.pm b/perl/Git/SVN.pm >>> > index 76b2965905..9b0caa3d47 100644 >>> > --- a/perl/Git/SVN.pm >>> > +++ b/perl/Git/SVN.pm >>> > @@ -999,7 +999,7 @@ sub restore_commit_header_env { >>> > } >>> > >>> > sub gc { >>> > - command_noisy('gc', '--auto'); >>> > + eval { command_noisy('gc', '--auto') }; >>> > }; >>> > >>> > sub do_git_commit { >>> > >>> > >>> > But yeah, somebody else who works on git regularly could >>> > probably stop repack from writing thousands of loose >>> > objects (and instead write a self-contained pack with >>> > those objects, instead). I haven't followed git closely >>> > lately, myself.
