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In order to make sure the cloned repository is good, we run "rev-list
--objects --not --all $new_refs" on the repository. This is expensive
on large repositories. This patch attempts to mitigate the impact in
this special case.
In the "good" clone case, we only have one pack. If all of the
following are met, we can be sure that all objects reachable from the
new refs exist, which is the intention of running "rev-list ...":
- all refs point to an object in the pack
- there are no dangling pointers in any object in the pack
- no objects in the pack point to objects outside the pack
The second and third checks can be done with the help of index-pack as
a slight variation of --strict check (which introduces a new condition
for the shortcut: pack transfer must be used and the number of objects
large enough to call index-pack). The first is checked in
check_everything_connected after we get an "ok" from index-pack.
"index-pack + new checks" is still faster than the current "index-pack
+ rev-list", which is the whole point of this patch. If any of the
conditions fail, we fall back to the good old but expensive "rev-list
..". In that case it's even more expensive because we have to pay for
the new checks in index-pack. But that should only happen when the
other side is either buggy or malicious.
Cloning linux-2.6 over file://
before after
real 3m25.693s 2m53.050s
user 5m2.037s 4m42.396s
sys 0m13.750s 0m16.574s
A more realistic test with ssh:// over wireless
before after
real 11m26.629s 10m4.213s
user 5m43.196s 5m19.444s
sys 0m35.812s 0m37.630s
This shortcut is not applied to shallow clones, partly because shallow
clones should have no more objects than a usual fetch and the cost of
rev-list is acceptable, partly to avoid dealing with corner cases when
grafting is involved.
This shortcut does not apply to unpack-objects code path either
because the number of objects must be small in order to trigger that
code path.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
103 lines
3.4 KiB
Text
103 lines
3.4 KiB
Text
git-index-pack(1)
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=================
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NAME
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----
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git-index-pack - Build pack index file for an existing packed archive
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SYNOPSIS
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--------
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[verse]
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'git index-pack' [-v] [-o <index-file>] <pack-file>
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'git index-pack' --stdin [--fix-thin] [--keep] [-v] [-o <index-file>]
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[<pack-file>]
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DESCRIPTION
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-----------
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Reads a packed archive (.pack) from the specified file, and
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builds a pack index file (.idx) for it. The packed archive
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together with the pack index can then be placed in the
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objects/pack/ directory of a Git repository.
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OPTIONS
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-------
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-v::
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Be verbose about what is going on, including progress status.
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-o <index-file>::
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Write the generated pack index into the specified
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file. Without this option the name of pack index
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file is constructed from the name of packed archive
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file by replacing .pack with .idx (and the program
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fails if the name of packed archive does not end
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with .pack).
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--stdin::
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When this flag is provided, the pack is read from stdin
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instead and a copy is then written to <pack-file>. If
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<pack-file> is not specified, the pack is written to
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objects/pack/ directory of the current Git repository with
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a default name determined from the pack content. If
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<pack-file> is not specified consider using --keep to
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prevent a race condition between this process and
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'git repack'.
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--fix-thin::
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Fix a "thin" pack produced by `git pack-objects --thin` (see
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linkgit:git-pack-objects[1] for details) by adding the
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excluded objects the deltified objects are based on to the
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pack. This option only makes sense in conjunction with --stdin.
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--keep::
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Before moving the index into its final destination
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create an empty .keep file for the associated pack file.
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This option is usually necessary with --stdin to prevent a
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simultaneous 'git repack' process from deleting
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the newly constructed pack and index before refs can be
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updated to use objects contained in the pack.
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--keep=<msg>::
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Like --keep create a .keep file before moving the index into
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its final destination, but rather than creating an empty file
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place '<msg>' followed by an LF into the .keep file. The '<msg>'
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message can later be searched for within all .keep files to
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locate any which have outlived their usefulness.
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--index-version=<version>[,<offset>]::
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This is intended to be used by the test suite only. It allows
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to force the version for the generated pack index, and to force
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64-bit index entries on objects located above the given offset.
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--strict::
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Die, if the pack contains broken objects or links.
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--check-self-contained-and-connected::
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Die if the pack contains broken links. For internal use only.
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--threads=<n>::
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Specifies the number of threads to spawn when resolving
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deltas. This requires that index-pack be compiled with
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pthreads otherwise this option is ignored with a warning.
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This is meant to reduce packing time on multiprocessor
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machines. The required amount of memory for the delta search
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window 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 use maximum 3 threads.
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Note
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----
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Once the index has been created, the list of object names is sorted
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and the SHA-1 hash of that list is printed to stdout. If --stdin was
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also used then this is prefixed by either "pack\t", or "keep\t" if a
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new .keep file was successfully created. This is useful to remove a
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.keep file used as a lock to prevent the race with 'git repack'
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mentioned above.
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GIT
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---
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Part of the linkgit:git[1] suite
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