tree 604d80863a05933137da93fd2cb8919eca6016ec
parent fbf20aeeef062e8cbd7db43788cfd3a69764071f
author Jeff King <peff@peff.net> 1614047120 -0500
committer Junio C Hamano <gitster@pobox.com> 1614065452 -0800

builtin/pack-objects.c: rewrite honor-pack-keep logic

Now that we have find_kept_pack_entry(), we don't have to manually keep
hunting through every pack to find a possible "kept" duplicate of the
object. This should be faster, assuming only a portion of your total
packs are actually kept.

Note that we have to re-order the logic a bit here; we can deal with the
disqualifying situations first (e.g., finding the object in a non-local
pack with --local), then "kept" situation(s), and then just fall back to
other "--local" conditions.

Here are the results from p5303 (measurements again taken on the
kernel):

  Test                                        HEAD^                   HEAD
  -----------------------------------------------------------------------------------------------
  5303.5: repack (1)                          57.26(54.59+10.84)      57.34(54.66+10.88) +0.1%
  5303.6: repack with kept (1)                57.33(54.80+10.51)      57.38(54.83+10.49) +0.1%
  5303.11: repack (50)                        71.54(88.57+4.84)       71.70(88.99+4.74) +0.2%
  5303.12: repack with kept (50)              85.12(102.05+4.94)      72.58(89.61+4.78) -14.7%
  5303.17: repack (1000)                      216.87(490.79+14.57)    217.19(491.72+14.25) +0.1%
  5303.18: repack with kept (1000)            665.63(938.87+15.76)    246.12(520.07+14.93) -63.0%

and the --stdin-packs timings:

  5303.7: repack with --stdin-packs (1)       0.01(0.01+0.00)         0.00(0.00+0.00) -100.0%
  5303.13: repack with --stdin-packs (50)     3.53(12.07+0.24)        3.43(11.75+0.24) -2.8%
  5303.19: repack with --stdin-packs (1000)   195.83(371.82+8.10)     130.50(307.15+7.66) -33.4%

So our repack with an empty .keep pack is roughly as fast as one without
a .keep pack up to 50 packs. But the --stdin-packs case scales a little
better, too.

Notably, it is faster than a repack of the same size and a kept pack. It
looks at fewer objects, of course, but the penalty for looking at many
packs isn't as costly.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>