[PATCH 2/2] pack-objects: compute local/ignore_pack_keep early
- From
Jeff King <peff@peff.net>
- Date
- Jul 25, 2016, 18:50 UTC
- Message-ID
- <20160725185031.GB12974@sigill.intra.peff.net>
- In-Reply-To
- <20160725184938.GA12871@sigill.intra.peff.net>
In want_object_in_pack(), we can exit early from our loop if neither "local" nor "ignore_pack_keep" are set. If they are, however, we must examine each pack to see if it has the object and is non-local or has a ".keep".
It's quite common for there to be no non-local or .keep packs at all, in which case we know ahead of time that looking further will be pointless. We can pre-compute this by simply iterating over the list of packs ahead of time, and dropping the flags if there are no packs that could match.
Another similar strategy would be to modify the loop in want_object_in_pack() to notice that we have already found the object once, and that we are looping only to check for "local" and "keep" attributes. If a pack has neither of those, we can skip the call to find_pack_entry_one(), which is the expensive part of the loop.
This has two advantages:
- it isn't all-or-nothing; we still get some improvement
when there's a small number of kept or non-local packs,
and a large number of non-kept local packs - it eliminates any possible race where we add new
non-local or kept packs after our initial scan. In
practice, I don't think this race matters; we already
cache the packed_git information, so somebody who adds a
new pack or .keep file after we've started will not be
noticed at all, unless we happen to need to call
reprepare_packed_git() because a lookup fails. In other words, we're already racy, and the race is not
a big deal (losing the race means we might include an
object in the pack that would not otherwise be, which is
an acceptable outcome).However, it also has a disadvantage: we still loop over the rest of the packs for each object to check their flags. This is much less expensive than doing the object lookup, but still not free. So if we wanted to implement that strategy to cover the non-all-or-nothing cases, we could do so in addition to this one (so you get the most speedup in the all-or-nothing case, and the best we can do in the other cases). But given that the all-or-nothing case is likely the most common, it is probably not worth the trouble, and we can revisit this later if evidence points otherwise.
Signed-off-by: Jeff King <peff@peff.net> --- builtin/pack-objects.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c index 55ef5a8..c5e343c 100644 --- a/builtin/pack-objects.c +++ b/builtin/pack-objects.c @@ -46,6 +46,7 @@ static int keep_unreachable, unpack_unreachable, include_tag; static unsigned long unpack_unreachable_expiration; static int pack_loose_unreachable; static int local; +static int have_non_local_packs; static int incremental; static int ignore_packed_keep; static int allow_ofs_delta; @@ -981,7 +982,7 @@ static int want_object_in_pack(const unsigned char *sha1, return 0; if (ignore_packed_keep && p->pack_local && p->pack_keep) return 0; - if (!ignore_packed_keep && !local) + if (!ignore_packed_keep && (!local || !have_non_local_packs)) break; } } @@ -2785,6 +2786,28 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix) progress = 2; prepare_packed_git(); + if (ignore_packed_keep) { + struct packed_git *p; + for (p = packed_git; p; p = p->next) + if (p->pack_local && p->pack_keep) + break; + if (!p) /* no keep-able packs found */ + ignore_packed_keep = 0; + } + if (local) { + /* + * unlike ignore_packed_keep above, we do not want to + * unset "local" based on looking at packs, as it + * also covers non-local objects + */ + struct packed_git *p; + for (p = packed_git; p; p = p->next) { + if (!p->pack_local) { + have_non_local_packs = 1; + break; + } + } + } if (progress) progress_state = start_progress(_("Counting objects"), 0);
-- 2.9.2.512.g8a06708