On Wed, Oct 12, 2016 at 07:01:43PM -0400, Jeff King wrote: > On Thu, Oct 13, 2016 at 12:30:52AM +0200, Vegard Nossum wrote: > > > However, the commit found by 'git blame' above appears just fine to me, > > I haven't been able to spot a bug in it. > > > > A closer inspection reveals the problem to really be that this is an > > extremely hot path with more than -- holy cow -- 4,106,756,451 > > iterations on the 'packed_git' list for a single 'git fetch' on my > > repository. I'm guessing the patch above just made the inner loop > > ever so slightly slower. > > > > My .git/objects/pack/ has ~2088 files (1042 idx files, 1042 pack files, > > and 4 tmp_pack_* files). > > Yeah. I agree that the commit you found makes the check a little more > expensive, but I think the root of the problem is calling > prepare_packed_git_one many times. This _should_ happen once for each > pack at program startup, and possibly again if we need to re-scan the > pack directory to account for racing with a simultaneous repack. > > The latter is generally triggered when we fail to look up an object we > expect to exist. So I'd suspect 45e8a74 (has_sha1_file: re-check pack > directory before giving up, 2013-08-30) is playing a part. We dealt with > that to some degree in 0eeb077 (index-pack: avoid excessive re-reading > of pack directory, 2015-06-09), but it would not surprise me if there is > another spot that needs similar treatment. > > Does the patch below help? Also, is it possible to make the repository in question available? I might be able to reproduce based on your description, but it would save time if I could directly run gdb on your example. Specifically, I'm interested in the call graph that leads to calling reprepare_packed_git(). -Peff