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2021-09-14midx.c: respect 'pack.writeBitmapHashcache' when writing bitmapsLibravatar Taylor Blau1-0/+4
In the previous commit, the bitmap writing code learned to propagate values from an existing hash-cache extension into the bitmap that it is writing. Now that that functionality exists, let's expose it by teaching the 'git multi-pack-index' builtin to respect the `pack.writeBitmapHashCache` option so that the hash-cache may be written at all. Two minor points worth noting here: - The 'git multi-pack-index write' sub-command didn't previously read any configuration (instead this is handled in the base command). A separate handler is added here to respect this write-specific config option. - I briefly considered adding a 'bitmap_flags' field to the static options struct, but decided against it since it would require plumbing through a new parameter to the write_midx_file() function. Instead, a new MIDX-specific flag is added, which is translated to the corresponding bitmap one. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-07-08Merge branch 'jk/doc-max-pack-size'Libravatar Junio C Hamano1-6/+17
Doc update. * jk/doc-max-pack-size: doc: warn people against --max-pack-size
2021-06-09doc: warn people against --max-pack-sizeLibravatar Jeff King1-6/+17
This option is almost never a good idea, as the resulting repository is larger and slower (see the new explanations in the docs). I outlined the potential problems. We could go further and make the option harder to find (or at least, make the command-line option descriptions a much more terse "you probably don't want this; see pack.packsizeLimit for details"). But this seems like a minimal change that may prevent people from thinking it's more useful than it is. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-03-31builtin/pack-objects.c: respect 'pack.preferBitmapTips'Libravatar Taylor Blau1-0/+15
When writing a new pack with a bitmap, it is sometimes convenient to indicate some reference prefixes which should receive priority when selecting which commits to receive bitmaps. A truly motivated caller could accomplish this by setting 'pack.islandCore', (since all commits in the core island are similarly marked as preferred) but this requires callers to opt into using delta islands, which they may or may not want to do. Introduce a new multi-valued configuration, 'pack.preferBitmapTips' to allow callers to specify a list of reference prefixes. All references which have a prefix contained in 'pack.preferBitmapTips' will mark their tips as "preferred" in the same way as commits are marked as preferred for selection by 'pack.islandCore'. The choice of the verb "prefer" is intentional: marking the NEEDS_BITMAP flag on an object does *not* guarantee that that object will receive a bitmap. It merely guarantees that that commit will receive a bitmap over any *other* commit in the same window by bitmap_writer_select_commits(). The test this patch adds reflects this quirk, too. It only tests that a commit (which didn't receive bitmaps by default) is selected for bitmaps after changing the value of 'pack.preferBitmapTips' to include it. Other commits may lose their bitmaps as a byproduct of how the selection process works (bitmap_writer_select_commits() ignores the remainder of a window after seeing a commit with the NEEDS_BITMAP flag). This configuration will aide in selecting important references for multi-pack bitmaps, since they do not respect the same pack.islandCore configuration. (They could, but doing so may be confusing, since it is packs--not bitmaps--which are influenced by the delta-islands configuration). In a fork network repository (one which lists all forks of a given repository as remotes), for example, it is useful to set pack.preferBitmapTips to 'refs/remotes/<root>/heads' and 'refs/remotes/<root>/tags', where '<root>' is an opaque identifier referring to the repository which is at the base of the fork chain. Suggested-by: Jeff King <peff@peff.net> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-01-25Documentation/config/pack.txt: advertise 'pack.writeReverseIndex'Libravatar Taylor Blau1-0/+7
Now that the pack.writeReverseIndex configuration is respected in both 'git index-pack' and 'git pack-objects' (and therefore, all of their callers), we can safely advertise it for use in the git-config manual. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-03-20config: set pack.useSparse=true by defaultLibravatar Derrick Stolee1-2/+2
The pack.useSparse config option was introduced by 3d036eb0 (pack-objects: create pack.useSparse setting, 2019-01-19) and was first available in v2.21.0. When enabled, the pack-objects process during 'git push' will use a sparse tree walk when deciding which trees and blobs to send to the remote. The algorithm was introduced by d5d2e93 (revision: implement sparse algorithm, 2019-01-16) and has been in production use by VFS for Git since around that time. The features.experimental config option also enabled pack.useSparse, so hopefully that has also increased exposure. It is worth noting that pack.useSparse has a possibility of sending more objects across a push, but requires a special arrangement of exact _copies_ across directories. There is a test in t5322-pack-objects-sparse.sh that demonstrates this possibility. This test uses the --sparse option to "git pack-objects" but we can make it implied by the config value to demonstrate that the default value has changed. While updating that test, I noticed that the documentation did not include an option for --no-sparse, which is now more important than it was before. Since the downside is unlikely but the upside is significant, set the default value of pack.useSparse to true. Remove it from the set of options implied by features.experimental. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-14Merge branch 'jk/packfile-reuse-cleanup'Libravatar Junio C Hamano1-0/+7
The way "git pack-objects" reuses objects stored in existing pack to generate its result has been improved. * jk/packfile-reuse-cleanup: pack-bitmap: don't rely on bitmap_git->reuse_objects pack-objects: add checks for duplicate objects pack-objects: improve partial packfile reuse builtin/pack-objects: introduce obj_is_packed() pack-objects: introduce pack.allowPackReuse csum-file: introduce hashfile_total() pack-bitmap: simplify bitmap_has_oid_in_uninteresting() pack-bitmap: uninteresting oid can be outside bitmapped packfile pack-bitmap: introduce bitmap_walk_contains() ewah/bitmap: introduce bitmap_word_alloc() packfile: expose get_delta_base() builtin/pack-objects: report reused packfile objects
2020-01-23pack-objects: introduce pack.allowPackReuseLibravatar Jeff King1-0/+7
Let's make it possible to configure if we want pack reuse or not. The main reason it might not be wanted is probably debugging and performance testing, though pack reuse _might_ cause larger packs, because we wouldn't consider the reused objects as bases for finding new deltas. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-08-13repo-settings: create feature.experimental settingLibravatar Derrick Stolee1-1/+2
The 'feature.experimental' setting includes config options that are not committed to become defaults, but could use additional testing. Update the following config settings to take new defaults, and to use the repo_settings struct if not already using them: * 'pack.useSparse=true' * 'fetch.negotiationAlgorithm=skipping' In the case of fetch.negotiationAlgorithm, the existing logic would load the config option only when about to use the setting, so had a die() statement on an unknown string value. This is removed as now the config is parsed under prepare_repo_settings(). In general, this die() is probably misplaced and not valuable. A test was removed that checked this die() statement executed. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-03-18pack-objects: default to writing bitmap hash-cacheLibravatar Jeff King1-3/+1
Enabling pack.writebitmaphashcache should always be a performance win. It costs only 4 bytes per object on disk, and the timings in ae4f07fbcc (pack-bitmap: implement optional name_hash cache, 2013-12-21) show it improving fetch and partial-bitmap clone times by 40-50%. The only reason we didn't enable it by default at the time is that early versions of JGit's bitmap reader complained about the presence of optional header bits it didn't understand. But that was changed in JGit's d2fa3987a (Use bitcheck to check for presence of OPT_FULL option, 2013-10-30), which made it into JGit v3.5.0 in late 2014. So let's turn this option on by default. It's backwards-compatible with all versions of Git, and if you are also using JGit on the same repository, you'd only run into problems using a version that's almost 5 years old. We'll drop the manual setting from all of our test scripts, including perf tests. This isn't strictly necessary, but it has two advantages: 1. If the hash-cache ever stops being enabled by default, our perf regression tests will notice. 2. We can use the modified perf tests to show off the behavior of an otherwise unconfigured repo, as shown below. These are the results of a few of a perf tests against linux.git that showed interesting results. You can see the expected speedup in 5310.4, which was noted in ae4f07fbcc. Curiously, 5310.8 did not improve (and actually got slower), despite seeing the opposite in ae4f07fbcc. I don't have an explanation for that. The tests from p5311 did not exist back then, but do show improvements (a smaller pack due to better deltas, which we found in less time). Test HEAD^ HEAD ------------------------------------------------------------------------------------- 5310.4: simulated fetch 7.39(22.70+0.25) 5.64(11.43+0.22) -23.7% 5310.8: clone (partial bitmap) 18.45(24.83+1.19) 19.94(28.40+1.36) +8.1% 5311.31: server (128 days) 0.41(1.13+0.05) 0.34(0.72+0.02) -17.1% 5311.32: size (128 days) 7.4M 7.0M -4.8% 5311.33: client (128 days) 1.33(1.49+0.06) 1.29(1.37+0.12) -3.0% Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-01-17pack-objects: create pack.useSparse settingLibravatar Derrick Stolee1-0/+9
The '--sparse' flag in 'git pack-objects' changes the algorithm used to enumerate objects to one that is faster for individual users pushing new objects that change only a small cone of the working directory. The sparse algorithm is not recommended for a server, which likely sends new objects that appear across the entire working directory. Create a 'pack.useSparse' setting that enables this new algorithm. This allows 'git push' to use this algorithm without passing a '--sparse' flag all the way through four levels of run_command() calls. If the '--no-sparse' flag is set, then this config setting is overridden. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-10-29config.txt: move pack.* to a separate fileLibravatar Nguyễn Thái Ngọc Duy1-0/+120
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>