d4316604f8
Enabling pack.writebitmaphashcache should always be a performance win. It costs only 4 bytes per object on disk, and the timings inae4f07fbcc(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 inae4f07fbcc. Curiously, 5310.8 did not improve (and actually got slower), despite seeing the opposite inae4f07fbcc. 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>
128 lines
5.7 KiB
Plaintext
128 lines
5.7 KiB
Plaintext
pack.window::
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The size of the window used by linkgit:git-pack-objects[1] when no
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window size is given on the command line. Defaults to 10.
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pack.depth::
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The maximum delta depth used by linkgit:git-pack-objects[1] when no
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maximum depth is given on the command line. Defaults to 50.
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Maximum value is 4095.
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pack.windowMemory::
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The maximum size of memory that is consumed by each thread
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in linkgit:git-pack-objects[1] for pack window memory when
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no limit is given on the command line. The value can be
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suffixed with "k", "m", or "g". When left unconfigured (or
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set explicitly to 0), there will be no limit.
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pack.compression::
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An integer -1..9, indicating the compression level for objects
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in a pack file. -1 is the zlib default. 0 means no
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compression, and 1..9 are various speed/size tradeoffs, 9 being
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slowest. If not set, defaults to core.compression. If that is
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not set, defaults to -1, the zlib default, which is "a default
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compromise between speed and compression (currently equivalent
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to level 6)."
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+
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Note that changing the compression level will not automatically recompress
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all existing objects. You can force recompression by passing the -F option
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to linkgit:git-repack[1].
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pack.island::
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An extended regular expression configuring a set of delta
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islands. See "DELTA ISLANDS" in linkgit:git-pack-objects[1]
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for details.
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pack.islandCore::
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Specify an island name which gets to have its objects be
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packed first. This creates a kind of pseudo-pack at the front
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of one pack, so that the objects from the specified island are
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hopefully faster to copy into any pack that should be served
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to a user requesting these objects. In practice this means
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that the island specified should likely correspond to what is
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the most commonly cloned in the repo. See also "DELTA ISLANDS"
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in linkgit:git-pack-objects[1].
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pack.deltaCacheSize::
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The maximum memory in bytes used for caching deltas in
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linkgit:git-pack-objects[1] before writing them out to a pack.
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This cache is used to speed up the writing object phase by not
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having to recompute the final delta result once the best match
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for all objects is found. Repacking large repositories on machines
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which are tight with memory might be badly impacted by this though,
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especially if this cache pushes the system into swapping.
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A value of 0 means no limit. The smallest size of 1 byte may be
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used to virtually disable this cache. Defaults to 256 MiB.
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pack.deltaCacheLimit::
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The maximum size of a delta, that is cached in
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linkgit:git-pack-objects[1]. This cache is used to speed up the
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writing object phase by not having to recompute the final delta
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result once the best match for all objects is found.
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Defaults to 1000. Maximum value is 65535.
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pack.threads::
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Specifies the number of threads to spawn when searching for best
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delta matches. This requires that linkgit:git-pack-objects[1]
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be compiled with pthreads otherwise this option is ignored with a
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warning. This is meant to reduce packing time on multiprocessor
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machines. The required amount of memory for the delta search window
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is however multiplied by the number of threads.
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Specifying 0 will cause Git to auto-detect the number of CPU's
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and set the number of threads accordingly.
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pack.indexVersion::
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Specify the default pack index version. Valid values are 1 for
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legacy pack index used by Git versions prior to 1.5.2, and 2 for
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the new pack index with capabilities for packs larger than 4 GB
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as well as proper protection against the repacking of corrupted
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packs. Version 2 is the default. Note that version 2 is enforced
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and this config option ignored whenever the corresponding pack is
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larger than 2 GB.
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+
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If you have an old Git that does not understand the version 2 `*.idx` file,
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cloning or fetching over a non native protocol (e.g. "http")
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that will copy both `*.pack` file and corresponding `*.idx` file from the
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other side may give you a repository that cannot be accessed with your
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older version of Git. If the `*.pack` file is smaller than 2 GB, however,
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you can use linkgit:git-index-pack[1] on the *.pack file to regenerate
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the `*.idx` file.
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pack.packSizeLimit::
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The maximum size of a pack. This setting only affects
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packing to a file when repacking, i.e. the git:// protocol
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is unaffected. It can be overridden by the `--max-pack-size`
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option of linkgit:git-repack[1]. Reaching this limit results
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in the creation of multiple packfiles; which in turn prevents
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bitmaps from being created.
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The minimum size allowed is limited to 1 MiB.
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The default is unlimited.
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Common unit suffixes of 'k', 'm', or 'g' are
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supported.
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pack.useBitmaps::
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When true, git will use pack bitmaps (if available) when packing
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to stdout (e.g., during the server side of a fetch). Defaults to
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true. You should not generally need to turn this off unless
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you are debugging pack bitmaps.
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pack.useSparse::
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When true, git will default to using the '--sparse' option in
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'git pack-objects' when the '--revs' option is present. This
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algorithm only walks trees that appear in paths that introduce new
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objects. This can have significant performance benefits when
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computing a pack to send a small change. However, it is possible
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that extra objects are added to the pack-file if the included
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commits contain certain types of direct renames.
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pack.writeBitmaps (deprecated)::
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This is a deprecated synonym for `repack.writeBitmaps`.
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pack.writeBitmapHashCache::
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When true, git will include a "hash cache" section in the bitmap
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index (if one is written). This cache can be used to feed git's
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delta heuristics, potentially leading to better deltas between
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bitmapped and non-bitmapped objects (e.g., when serving a fetch
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between an older, bitmapped pack and objects that have been
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pushed since the last gc). The downside is that it consumes 4
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bytes per object of disk space. Defaults to true.
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