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[PATCH v3] repack: enable bitmaps by default on bare repos

From
EWEric Wong <e@80x24.org>
Date
Mar 14, 2019, 09:12 UTC
Message-ID
<20190314091254.nescpfp3n6mbjpmh@dcvr>
In-Reply-To
<20190313145417.GA24101@sigill.intra.peff.net>
Jeff King <peff@peff.net> wrote:
Show 11 quoted lines
> On Wed, Mar 13, 2019 at 01:51:33AM +0000, Eric Wong wrote:
> 
> > But I did find Ævar's forgotten gitperformance doc and thread
> > where the topic was brought up:
> > 
> >   https://public-inbox.org/git/20170403211644.26814-1-avarab@gmail.com/
> 
> One thing that thread reminded me of: we probably also want to default
> pack.writebitmaphashcache on. Otherwise the time saved during the object
> enumeration can backfire when we spend much more time trying delta
> compression (because we don't know the pathnames of any objects).

Interesting... I found a big improvement with public-inbox just using bitmaps; but have never tried the hash cache.

> The reason it defaults to off is for on-disk compatibility with JGit.

Right. Our documentation seems to indicate JGit just warns (but doesn't fall over), so maybe that can be considered separately.

I've never used JGit myself; and was satisfied enough with bitmaps alone that I never tried the hash-cache.

> But I have very little experience running without the hash-cache on. We
> added it very early on because we found performance was not great
> without it (I don't know if people running JGit have run into the same
> problem and if not, why not).

As far as serving clones and fetches, public-inbox-init has always created bare repos with bitmaps enabled, but without the hash-cache for compatibility concerns.

That's a lot of fetches and clones over the years.
Show 6 quoted lines
> > +test_expect_success 'incremental repack does not complain' '
> > +	git -C bare.git repack -q 2>repack.err &&
> > +	! test -s repack.err
> > +'
> 
> This last line could use "test_must_be_empty".
Thanks for the review!
---------8<-----------
Subject: [PATCH] repack: enable bitmaps by default on bare repos

A typical use case for bare repos is for serving clones and fetches to clients. Enable bitmaps by default on bare repos to make it easier for admins to host git repos in a performant way.

Signed-off-by: Eric Wong <e@80x24.org>
Helped-by: Jeff King <peff@peff.net>
---
 Documentation/config/repack.txt |  2 +-
 builtin/repack.c                |  5 ++++-
 t/t7700-repack.sh               | 19 ++++++++++++++++++-
 3 files changed, 23 insertions(+), 3 deletions(-)
diff --git a/Documentation/config/repack.txt b/Documentation/config/repack.txt
index a5c37813fd..9c413e177e 100644
--- a/Documentation/config/repack.txt
+++ b/Documentation/config/repack.txt
@@ -24,4 +24,4 @@ repack.writeBitmaps::
 	packs created for clones and fetches, at the cost of some disk
 	space and extra time spent on the initial repack.  This has
 	no effect if multiple packfiles are created.
-	Defaults to false.
+	Defaults to true on bare repos, false otherwise.
diff --git a/builtin/repack.c b/builtin/repack.c
index 67f8978043..caca113927 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -14,7 +14,7 @@
 
 static int delta_base_offset = 1;
 static int pack_kept_objects = -1;
-static int write_bitmaps;
+static int write_bitmaps = -1;
 static int use_delta_islands;
 static char *packdir, *packtmp;
 
@@ -343,6 +343,9 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	    (unpack_unreachable || (pack_everything & LOOSEN_UNREACHABLE)))
 		die(_("--keep-unreachable and -A are incompatible"));
 
+	if (write_bitmaps < 0)
+		write_bitmaps = (pack_everything & ALL_INTO_ONE) &&
+				 is_bare_repository();
 	if (pack_kept_objects < 0)
 		pack_kept_objects = write_bitmaps;
 
diff --git a/t/t7700-repack.sh b/t/t7700-repack.sh
index 6162e2a8e6..86d05160a3 100755
--- a/t/t7700-repack.sh
+++ b/t/t7700-repack.sh
@@ -221,5 +221,22 @@ test_expect_success 'repack --keep-pack' '
 	)
 '
 
-test_done
+test_expect_success 'bitmaps are created by default in bare repos' '
+	git clone --bare .git bare.git &&
+	git -C bare.git repack -ad &&
+	bitmap=$(ls bare.git/objects/pack/*.bitmap) &&
+	test_path_is_file "$bitmap"
+'
+
+test_expect_success 'incremental repack does not complain' '
+	git -C bare.git repack -q 2>repack.err &&
+	test_must_be_empty repack.err
+'
 
+test_expect_success 'bitmaps can be disabled on bare repos' '
+	git -c repack.writeBitmaps=false -C bare.git repack -ad &&
+	bitmap=$(ls bare.git/objects/pack/*.bitmap 2>/dev/null || :) &&
+	test -z "$bitmap"
+'
+
+test_done

-- 
EW
Previous: Jeff KingNext: Jeff King
Message 14 of 57 in “some prune optimizations”
  1. 0/3 some prune optimizationsJeff King, Feb 14, 2019
  2. 1/3 prune: lazily perform reachability traversalJeff King, Feb 14, 2019
  3. Eric SunshineFeb 14, 2019
  4. Jeff KingFeb 14, 2019
  5. 2/3 prune: use bitmaps for reachability traversalJeff King, Feb 14, 2019
  6. bitmaps by default? [was: prune: use bitmaps for reachability traversal]Eric Wong, Mar 9, 2019
  7. Jeff KingMar 10, 2019
  8. repack: enable bitmaps by default on bare reposEric Wong, Mar 12, 2019
  9. Ævar Arnfjörð BjarmasonMar 12, 2019
  10. Jeff KingMar 12, 2019
  11. Jeff KingMar 12, 2019
  12. Eric WongMar 13, 2019
  13. Jeff KingMar 13, 2019
  14. repack: enable bitmaps by default on bare reposEric Wong, Mar 14, 2019
  15. Jeff KingMar 14, 2019
  16. 0/2 enable bitmap hash-cache by defaultJeff King, Mar 15, 2019
  17. 1/2 t5310: correctly remove bitmaps for jgit testJeff King, Mar 15, 2019
  18. SZEDER GáborMar 15, 2019
  19. Jeff KingMar 15, 2019
  20. 2/2 pack-objects: default to writing bitmap hash-cacheJeff King, Mar 15, 2019
  21. Ævar Arnfjörð BjarmasonApr 9, 2019
  22. Jeff KingApr 10, 2019
  23. Junio C HamanoApr 25, 2019
  24. Jeff KingMay 4, 2019
  25. Ævar Arnfjörð BjarmasonMay 4, 2019
  26. SZEDER GáborMay 4, 2019
  27. Ævar Arnfjörð BjarmasonMay 8, 2019
  28. Junio C HamanoMay 9, 2019
  29. Jeff KingMay 7, 2019
  30. Ævar Arnfjörð BjarmasonMay 7, 2019
  31. Jeff KingMay 8, 2019
  32. Derrick StoleeMay 8, 2019
  33. Ævar Arnfjörð BjarmasonMay 8, 2019
  34. Jeff KingMay 8, 2019
  35. Jeff KingMay 23, 2019
  36. Derrick StoleeMay 23, 2019
  37. Jeff KingMay 24, 2019
  38. Derrick StoleeMay 24, 2019
  39. Ævar Arnfjörð BjarmasonMay 23, 2019
  40. Jeff KingMay 24, 2019
  41. Ævar Arnfjörð BjarmasonMay 24, 2019
  42. Jeff KingMay 24, 2019
  43. Ævar Arnfjörð BjarmasonMay 24, 2019
  44. SZEDER GáborMay 24, 2019
  45. Ævar Arnfjörð BjarmasonMay 24, 2019
  46. SZEDER GáborMay 24, 2019
  47. Ævar Arnfjörð BjarmasonMay 24, 2019
  48. SZEDER GáborMay 24, 2019
  49. Ævar Arnfjörð BjarmasonMay 24, 2019
  50. pack-bitmap: look for an uninteresting bitmapDerrick Stolee, May 24, 2019
  51. Derrick StoleeApr 15, 2019
  52. Jeff KingApr 18, 2019
  53. t5304: add a test for pruning with bitmapsJeff King, Apr 18, 2019
  54. Derrick StoleeApr 20, 2019
  55. Jeff KingApr 20, 2019
  56. Derrick StoleeApr 20, 2019
  57. 3/3 prune: check SEEN flag for reachabilityJeff King, Feb 14, 2019

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