On 08/17, Jeff King wrote: > On Thu, Aug 17, 2017 at 05:12:50PM +0200, Michael Haggerty wrote: > > > I was testing this using the reporter's recipe (but fetching from a > > local clone), and found the following surprising timing numbers: > > > > b05855b5bc (before the slowdown): 22.7 s > > 524a9fdb51 (immediately after the slowdown): 13 minutes > > 4e81f1ecf1 (after this fix): 14.5 s > > > > The fact that the fetch is now significantly *faster* than before the > > slowdown seems not to have anything to do with the reference code. > > I bisected this (with some hackery, since the commits in the middle all > take 13 minutes to run). The other speedup is indeed unrelated, and is > due to Brandon's aacc5c1a81 (submodule: refactor logic to determine > changed submodules, 2017-05-01). > > The commit message doesn't mention performance (it's mostly about code > reduction). I think the speedup comes from using > diff_tree_combined_merge() instead of manually diffing each commit > against its parents. But I didn't do further timings to verify that (I'm > reporting it here mostly as an interesting curiosity for submodule > folks). Haha always great to see an unintended improvement in performance! Yeah that commit was mostly about removing duplicate code but I'm glad that it ended up being a benefit to perf too. > > > diff --git a/refs/files-backend.c b/refs/files-backend.c > > index e9b95592b6..f2a420c611 100644 > > --- a/refs/files-backend.c > > +++ b/refs/files-backend.c > > @@ -631,11 +631,11 @@ static int lock_raw_ref(struct files_ref_store *refs, > > > > /* > > * If the ref did not exist and we are creating it, > > - * make sure there is no existing ref that conflicts > > - * with refname: > > + * make sure there is no existing packed ref that > > + * conflicts with refname: > > */ > > if (refs_verify_refname_available( > > - &refs->base, refname, > > + refs->packed_ref_store, refname, > > extras, skip, err)) > > goto error_return; > > } > > This seems too easy to be true. :) But I think it matches what we were > doing before 524a9fdb51 (so it's correct), and the performance numbers > don't lie. > > -Peff -- Brandon Williams
