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The way .git/index and .git/sharedindex* files were initially
created gave these files different perm bits until they were
adjusted for shared repository settings. This was made consistent.
* cc/shared-index-permbits:
read-cache: make the split index obey umask settings
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If a user explicitly sets
[index]
threads = true
to read the index using multiple threads, ensure that index writes
include the offset table by default to make that possible. This
ensures that the user's intent of turning on threading is respected.
In other words, permit the following configurations:
- index.threads and index.recordOffsetTable unspecified: do not write
the offset table yet (to avoid alarming the user with "ignoring IEOT
extension" messages when an older version of Git accesses the
repository) but do make use of multiple threads to read the index if
the supporting offset table is present.
This can also be requested explicitly by setting index.threads=true,
0, or >1 and index.recordOffsetTable=false.
- index.threads=false or 1: do not write the offset table, and do not
make use of the offset table.
One can set index.recordOffsetTable=false as well, to be more
explicit.
- index.threads=true, 0, or >1 and index.recordOffsetTable unspecified:
write the offset table and make use of threads at read time.
This can also be requested by setting index.threads=true, 0, >1, or
unspecified and index.recordOffsetTable=true.
Fortunately the complication is temporary: once most Git installations
have upgraded to a version with support for the IEOT and EOIE
extensions, we can flip the defaults for index.recordEndOfIndexEntries
and index.recordOffsetTable to true and eliminate the settings.
Helped-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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As with EOIE, popular versions of Git do not support the new IEOT
extension yet. When accessing a Git repository written by a more
modern version of Git, they correctly ignore the unrecognized section,
but in the process they loudly warn
ignoring IEOT extension
resulting in confusion for users. Introduce the index extension more
gently by not writing it yet in this first version with support for
it. Soon, once sufficiently many users are running a modern version
of Git, we can flip the default so users benefit from this index
extension by default.
Introduce a '[index] recordOffsetTable' configuration variable to
control whether the new index extension is written.
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Since 3b1d9e04 (eoie: add End of Index Entry (EOIE) extension,
2018-10-10) Git defaults to writing the new EOIE section when writing
out an index file. Usually that is a good thing because it improves
threaded performance, but when a Git repository is shared with older
versions of Git, it produces a confusing warning:
$ git status
ignoring EOIE extension
HEAD detached at 371ed0defa
nothing to commit, working tree clean
Let's introduce the new index extension more gently. First we'll roll
out the new version of Git that understands it, and then once
sufficiently many users are using such a version, we can flip the
default to writing it by default.
Introduce a '[index] recordEndOfIndexEntries' configuration variable
to allow interested users to benefit from this index extension early.
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Make the split index write out its .git/sharedindex_* files with the
same permissions as .git/index. This only changes the behavior when
core.sharedRepository isn't set, i.e. the user's umask settings will
be respected.
This hasn't been the case ever since the split index was originally
implemented in c18b80a0e8 ("update-index: new options to
enable/disable split index mode", 2014-06-13). A mkstemp()-like
function has always been used to create it. First mkstemp() itself,
and then later our own mkstemp()-like in
f6ecc62dbf ("write_shared_index(): use tempfile module", 2015-08-10)
A related bug was fixed in df801f3f9f ("read-cache: use shared perms
when writing shared index", 2017-06-25). Since then the split index
has respected core.sharedRepository.
However, using that setting should not be required simply to make git
obey the user's umask setting. It's intended for the use-case of
overriding whatever that umask is set to. This fixes cases where the
user has e.g. set his umask to 022 on a shared server in anticipation
of other user's needing to run "status", "log" etc. in his repository.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The codebase has been cleaned up to reduce "#ifndef NO_PTHREADS".
* nd/pthreads:
Clean up pthread_create() error handling
read-cache.c: initialize copy_len to shut up gcc 8
read-cache.c: reduce branching based on HAVE_THREADS
read-cache.c: remove #ifdef NO_PTHREADS
pack-objects: remove #ifdef NO_PTHREADS
preload-index.c: remove #ifdef NO_PTHREADS
grep: clean up num_threads handling
grep: remove #ifdef NO_PTHREADS
attr.c: remove #ifdef NO_PTHREADS
name-hash.c: remove #ifdef NO_PTHREADS
index-pack: remove #ifdef NO_PTHREADS
send-pack.c: move async's #ifdef NO_PTHREADS back to run-command.c
run-command.h: include thread-utils.h instead of pthread.h
thread-utils: macros to unconditionally compile pthreads API
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The helper function to refresh the cached stat information in the
in-core index has learned to perform the lstat() part of the
operation in parallel on multi-core platforms.
* bp/refresh-index-using-preload:
refresh_index: remove unnecessary calls to preload_index()
speed up refresh_index() by utilizing preload_index()
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Trivial bugfix.
* nd/unpack-trees-with-cache-tree:
read-cache: use of memory after it is freed
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It was reported that when building with NO_PTHREADS=1,
-Wmaybe-uninitialized is triggered. Just initialize the variable from
the beginning to shut the compiler up (because this warning is enabled
in config.dev)
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This is a faithful conversion with no attempt to clean up whatsoever.
Code indentation is left broken. There will be another commit to clean
it up and un-indent if we just indent now. It's just more code noise.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Speed up refresh_index() by utilizing preload_index() to do most of the work
spread across multiple threads. This works because most cache entries will
get marked CE_UPTODATE so that refresh_cache_ent() can bail out early when
called from within refresh_index().
On a Windows repo with ~200K files, this drops refresh times from 6.64
seconds to 2.87 seconds for a savings of 57%.
Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The codepath to support the experimental split-index mode had
remaining "racily clean" issues fixed.
* sg/split-index-racefix:
split-index: BUG() when cache entry refers to non-existing shared entry
split-index: smudge and add racily clean cache entries to split index
split-index: don't compare cached data of entries already marked for split index
split-index: count the number of deleted entries
t1700-split-index: date back files to avoid racy situations
split-index: add tests to demonstrate the racy split index problem
t1700-split-index: document why FSMONITOR is disabled in this test script
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introduced with c46c406ae1e (trace.h: support nested performance tracing)
on Aug 18, 2018 but not affecting maint
Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Acked-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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"git status" learns to show progress bar when refreshing the index
takes a long time.
* nd/status-refresh-progress:
status: show progress bar if refreshing the index takes too long
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A new extension to the index file has been introduced, which allows
the file to be read in parallel.
* bp/read-cache-parallel:
read-cache: load cache entries on worker threads
ieot: add Index Entry Offset Table (IEOT) extension
read-cache: load cache extensions on a worker thread
config: add new index.threads config setting
eoie: add End of Index Entry (EOIE) extension
read-cache: clean up casting and byte decoding
read-cache.c: optimize reading index format v4
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Various codepaths in the core-ish part learn to work on an
arbitrary in-core index structure, not necessarily the default
instance "the_index".
* nd/the-index: (23 commits)
revision.c: reduce implicit dependency the_repository
revision.c: remove implicit dependency on the_index
ws.c: remove implicit dependency on the_index
tree-diff.c: remove implicit dependency on the_index
submodule.c: remove implicit dependency on the_index
line-range.c: remove implicit dependency on the_index
userdiff.c: remove implicit dependency on the_index
rerere.c: remove implicit dependency on the_index
sha1-file.c: remove implicit dependency on the_index
patch-ids.c: remove implicit dependency on the_index
merge.c: remove implicit dependency on the_index
merge-blobs.c: remove implicit dependency on the_index
ll-merge.c: remove implicit dependency on the_index
diff-lib.c: remove implicit dependency on the_index
read-cache.c: remove implicit dependency on the_index
diff.c: remove implicit dependency on the_index
grep.c: remove implicit dependency on the_index
diff.c: remove the_index dependency in textconv() functions
blame.c: rename "repo" argument to "r"
combine-diff.c: remove implicit dependency on the_index
...
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Ever since the split index feature was introduced [1], refreshing a
split index is prone to a variant of the classic racy git problem.
Consider the following sequence of commands updating the split index
when the shared index contains a racily clean cache entry, i.e. an
entry whose cached stat data matches with the corresponding file in
the worktree and the cached mtime matches that of the index:
echo "cached content" >file
git update-index --split-index --add file
echo "dirty worktree" >file # size stays the same!
# ... wait ...
git update-index --add other-file
Normally, when a non-split index is updated, then do_write_index()
(the function responsible for writing all kinds of indexes, "regular",
split, and shared) recognizes racily clean cache entries, and writes
them with smudged stat data, i.e. with file size set to 0. When
subsequent git commands read the index, they will notice that the
smudged stat data doesn't match with the file in the worktree, and
then go on to check the file's content and notice its dirtiness.
In the above example, however, in the second 'git update-index'
prepare_to_write_split_index() decides which cache entries stored only
in the shared index should be replaced in the new split index. Alas,
this function never looks out for racily clean cache entries, and
since the file's stat data in the worktree hasn't changed since the
shared index was written, it won't be replaced in the new split index.
Consequently, do_write_index() doesn't even get this racily clean
cache entry, and can't smudge its stat data. Subsequent git commands
will then see that the index has more recent mtime than the file and
that the (not smudged) cached stat data still matches with the file in
the worktree, and, ultimately, will erroneously consider the file
clean.
Modify prepare_to_write_split_index() to recognize racily clean cache
entries, and mark them to be added to the split index. Note that
there are two places where it should check raciness: first those cache
entries that are only stored in the shared index, and then those that
have been copied by unpack_trees() from the shared index while it
constructed a new index. This way do_write_index() will get these
racily clean cache entries as well, and will then write them with
smudged stat data to the new split index.
This change makes all tests in 't1701-racy-split-index.sh' pass, so
flip the two 'test_expect_failure' tests to success. Also add the '#'
(as in nr. of trial) to those tests' description that were omitted
when the tests expected failure.
Note that after this change if the index is split when it contains a
racily clean cache entry, then a smudged cache entry will be written
both to the new shared and to the new split indexes. This doesn't
affect regular git commands: as far as they are concerned this is just
an entry in the split index replacing an outdated entry in the shared
index. It did affect a few tests in 't1700-split-index.sh', though,
because they actually check which entries are stored in the split
index; a previous patch in this series has already made the necessary
adjustments in 't1700'. And racily clean cache entries and index
splitting are rare enough to not worry about the resulting duplicated
smudged cache entries, and the additional complexity required to
prevent them is not worth it.
Several tests failed occasionally when the test suite was run with
'GIT_TEST_SPLIT_INDEX=yes'. Here are those that I managed to trace
back to this racy split index problem, starting with those failing
more frequently, with a link to a failing Travis CI build job for
each. The highlighted line [2] shows when the racy file was written,
which is not always in the failing test but in a preceeding setup
test.
t3903-stash.sh:
https://travis-ci.org/git/git/jobs/385542084#L5858
t4024-diff-optimize-common.sh:
https://travis-ci.org/git/git/jobs/386531969#L3174
t4015-diff-whitespace.sh:
https://travis-ci.org/git/git/jobs/360797600#L8215
t2200-add-update.sh:
https://travis-ci.org/git/git/jobs/382543426#L3051
t0090-cache-tree.sh:
https://travis-ci.org/git/git/jobs/416583010#L3679
There might be others, e.g. perhaps 't1000-read-tree-m-3way.sh' and
others using 'lib-read-tree-m-3way.sh', but I couldn't confirm yet.
[1] In the branch leading to the merge commit v2.1.0-rc0~45 (Merge
branch 'nd/split-index', 2014-07-16).
[2] Note that those highlighted lines are in the 'after failure' fold,
and your browser might unhelpfully fold it up before you could
take a good look.
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This patch helps address the CPU cost of loading the index by utilizing
the Index Entry Offset Table (IEOT) to divide loading and conversion of
the cache entries across multiple threads in parallel.
I used p0002-read-cache.sh to generate some performance data:
Test w/100,000 files reduced the time by 32.24%
Test w/1,000,000 files reduced the time by -4.77%
Note that on the 1,000,000 files case, multi-threading the cache entry parsing
does not yield a performance win. This is because the cost to parse the
index extensions in this repo, far outweigh the cost of loading the cache
entries.
The high cost of parsing the index extensions is driven by the cache tree
and the untracked cache extensions. As this is currently the longest pole,
any reduction in this time will reduce the overall index load times so is
worth further investigation in another patch series.
Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This patch enables addressing the CPU cost of loading the index by adding
additional data to the index that will allow us to efficiently multi-
thread the loading and conversion of cache entries.
It accomplishes this by adding an (optional) index extension that is a
table of offsets to blocks of cache entries in the index file. To make
this work for V4 indexes, when writing the cache entries, it periodically
"resets" the prefix-compression by encoding the current entry as if the
path name for the previous entry is completely different and saves the
offset of that entry in the IEOT. Basically, with V4 indexes, it
generates offsets into blocks of prefix-compressed entries.
Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This patch helps address the CPU cost of loading the index by loading
the cache extensions on a worker thread in parallel with loading the cache
entries.
In some cases, loading the extensions takes longer than loading the
cache entries so this patch utilizes the new EOIE to start the thread to
load the extensions before loading all the cache entries in parallel.
This is possible because the current extensions don't access the cache
entries in the index_state structure so are OK that they don't all exist
yet.
The CACHE_EXT_TREE, CACHE_EXT_RESOLVE_UNDO, and CACHE_EXT_UNTRACKED
extensions don't even get a pointer to the index so don't have access to the
cache entries.
CACHE_EXT_LINK only uses the index_state to initialize the split index.
CACHE_EXT_FSMONITOR only uses the index_state to save the fsmonitor last
update and dirty flags.
I used p0002-read-cache.sh to generate some performance data:
Test w/100,000 files reduced the time by 0.53%
Test w/1,000,000 files reduced the time by 27.78%
Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The End of Index Entry (EOIE) is used to locate the end of the variable
length index entries and the beginning of the extensions. Code can take
advantage of this to quickly locate the index extensions without having
to parse through all of the index entries.
The EOIE extension is always written out to the index file including to
the shared index when using the split index feature. Because it is always
written out, the SHA checksums in t/t1700-split-index.sh were updated
to reflect its inclusion.
It is written as an optional extension to ensure compatibility with other
git implementations that do not yet support it. It is always written out
to ensure it is available as often as possible to speed up index operations.
Because it must be able to be loaded before the variable length cache
entries and other index extensions, this extension must be written last.
The signature for this extension is { 'E', 'O', 'I', 'E' }.
The extension consists of:
- 32-bit offset to the end of the index entries
- 160-bit SHA-1 over the extension types and their sizes (but not
their contents). E.g. if we have "TREE" extension that is N-bytes
long, "REUC" extension that is M-bytes long, followed by "EOIE",
then the hash would be:
SHA-1("TREE" + <binary representation of N> +
"REUC" + <binary representation of M>)
Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This patch does a clean up pass to minimize the casting required to work
with the memory mapped index (mmap).
It also makes the decoding of network byte order more consistent by using
get_be32() where possible.
Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Index format v4 requires some more computation to assemble a path
based on a previous one. The current code is not very efficient
because
- it doubles memory copy, we assemble the final path in a temporary
first before putting it back to a cache_entry
- strbuf_remove() in expand_name_field() is not exactly a good fit
for stripping a part at the end, _setlen() would do the same job
and is much cheaper.
- the open-coded loop to find the end of the string in
expand_name_field() can't beat an optimized strlen()
This patch avoids the temporary buffer and writes directly to the new
cache_entry, which addresses the first two points. The last point
could also be avoided if the total string length fits in the first 12
bits of ce_flags, if not we fall back to strlen().
Running "test-tool read-cache 100" on webkit.git (275k files), reading
v2 only takes 4.226 seconds, while v4 takes 5.711 seconds, 35% more
time. The patch reduces read time on v4 to 4.319 seconds.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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A new variant repo_diff_setup() is added that takes 'struct repository *'
and diff_setup() becomes a thin macro around it that is protected by
NO_THE_REPOSITORY_COMPATIBILITY_MACROS, similar to NO_THE_INDEX_....
The plan is these macros will always be defined for all library files
and the macros are only accessible in builtin/
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This function calls do_diff_cache() which eventually needs to set this
"istate" to unpack_options->src_index [1]. This is an unfortunate fact
that unpack_trees() _will_ update [2] src_index so we can't really pass a
const index_state there. Just remove 'const'.
[1] Right now diff_cache() in diff-lib.c assigns the_index to
src_index. But the plan is to get rid of the_index, so it should
be 'istate' from here that gets assigned to src_index.
[2] Some transient bits in the source index are touched. Optional
extensions can also be removed. But other than that the source
tree should still be valid.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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spatch transformation to replace boolean uses of !hashcmp() to
newly introduced oideq() is added, and applied, to regain
performance lost due to support of multiple hash algorithms.
* jk/cocci:
show_dirstat: simplify same-content check
read-cache: use oideq() in ce_compare functions
convert hashmap comparison functions to oideq()
convert "hashcmp() != 0" to "!hasheq()"
convert "oidcmp() != 0" to "!oideq()"
convert "hashcmp() == 0" to hasheq()
convert "oidcmp() == 0" to oideq()
introduce hasheq() and oideq()
coccinelle: use <...> for function exclusion
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The unpack_trees() API used in checking out a branch and merging
walks one or more trees along with the index. When the cache-tree
in the index tells us that we are walking a tree whose flattened
contents is known (i.e. matches a span in the index), as linearly
scanning a span in the index is much more efficient than having to
open tree objects recursively and listing their entries, the walk
can be optimized, which is done in this topic.
* nd/unpack-trees-with-cache-tree:
Document update for nd/unpack-trees-with-cache-tree
cache-tree: verify valid cache-tree in the test suite
unpack-trees: add missing cache invalidation
unpack-trees: reuse (still valid) cache-tree from src_index
unpack-trees: reduce malloc in cache-tree walk
unpack-trees: optimize walking same trees with cache-tree
unpack-trees: add performance tracing
trace.h: support nested performance tracing
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Refreshing the index is usually very fast, but it can still take a
long time sometimes. Cold cache is one. Or copying a repo to a new
place (*). It's good to show something to let the user know "git
status" is not hanging, it's just busy doing something.
(*) In this case, all stat info in the index becomes invalid and git
falls back to rehashing all file content to see if there's any
difference between updating stat info in the index. This is quite
expensive. Even with a repo as small as git.git, it takes 3
seconds.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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These functions return the full oidcmp() value, but the
callers really only care whether it is non-zero. We can use
the more strict !oideq(), which a compiler may be able to
optimize further.
This does change the meaning of the return value subtly, but
it's unlikely that anybody would try to use them for
ordering. They're static-local in this file, and they
already return other error values that would confuse an
ordering (e.g., open() failure gives -1).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This rounds out the previous three patches, covering the
inequality logic for the "hash" variant of the functions.
As with the previous three, the accompanying code changes
are the mechanical result of applying the coccinelle patch;
see those patches for more discussion.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This is the flip side of the previous two patches: checking
for a non-zero oidcmp() can be more strictly expressed as
inequality. Like those patches, we write "!= 0" in the
coccinelle transformation, which covers by isomorphism the
more common:
if (oidcmp(E1, E2))
As with the previous two patches, this patch can be achieved
almost entirely by running "make coccicheck"; the only
differences are manual line-wrap fixes to match the original
code.
There is one thing to note for anybody replicating this,
though: coccinelle 1.0.4 seems to miss the case in
builtin/tag.c, even though it's basically the same as all
the others. Running with 1.0.7 does catch this, so
presumably it's just a coccinelle bug that was fixed in the
interim.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Using the more restrictive oideq() should, in the long run,
give the compiler more opportunities to optimize these
callsites. For now, this conversion should be a complete
noop with respect to the generated code.
The result is also perhaps a little more readable, as it
avoids the "zero is equal" idiom. Since it's so prevalent in
C, I think seasoned programmers tend not to even notice it
anymore, but it can sometimes make for awkward double
negations (e.g., we can drop a few !!oidcmp() instances
here).
This patch was generated almost entirely by the included
coccinelle patch. This mechanical conversion should be
completely safe, because we check explicitly for cases where
oidcmp() is compared to 0, which is what oideq() is doing
under the hood. Note that we don't have to catch "!oidcmp()"
separately; coccinelle's standard isomorphisms make sure the
two are treated equivalently.
I say "almost" because I did hand-edit the coccinelle output
to fix up a few style violations (it mostly keeps the
original formatting, but sometimes unwraps long lines).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The more library-ish parts of the codebase learned to work on the
in-core index-state instance that is passed in by their callers,
instead of always working on the singleton "the_index" instance.
* nd/no-the-index: (24 commits)
blame.c: remove implicit dependency on the_index
apply.c: remove implicit dependency on the_index
apply.c: make init_apply_state() take a struct repository
apply.c: pass struct apply_state to more functions
resolve-undo.c: use the right index instead of the_index
archive-*.c: use the right repository
archive.c: avoid access to the_index
grep: use the right index instead of the_index
attr: remove index from git_attr_set_direction()
entry.c: use the right index instead of the_index
submodule.c: use the right index instead of the_index
pathspec.c: use the right index instead of the_index
unpack-trees: avoid the_index in verify_absent()
unpack-trees: convert clear_ce_flags* to avoid the_index
unpack-trees: don't shadow global var the_index
unpack-trees: add a note about path invalidation
unpack-trees: remove 'extern' on function declaration
ls-files: correct index argument to get_convert_attr_ascii()
preload-index.c: use the right index instead of the_index
dir.c: remove an implicit dependency on the_index in pathspec code
...
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This makes sure that cache-tree is consistent with the index. The main
purpose is to catch potential problems by saving the index in
unpack_trees() but the line in write_index() would also help spot
missing invalidation in other code.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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We do n-way merge by walking the source index and n trees at the same
time and add merge results to a new temporary index called o->result.
The merge result for any given path could be either
- keep_entry(): same old index entry in o->src_index is reused
- merged_entry(): either a new entry is added, or an existing one updated
- deleted_entry(): one entry from o->src_index is removed
For some reason [1] we keep making sure that the source index's
cache-tree is still valid if used by o->result: for all those
merged/deleted entries, we invalidate the same path in o->src_index,
so only cache-trees covering the "keep_entry" parts remain good.
Because of this, the cache-tree from o->src_index can be perfectly
reused in o->result. And in fact we already rely on this logic to
reuse untracked cache in edf3b90553 (unpack-trees: preserve index
extensions - 2017-05-08). Move the cache-tree to o->result before
doing cache_tree_update() to reduce hashing cost.
Since cache_tree_update() has risen up as one of the most expensive
parts in unpack_trees() after the last few patches. This does help
reduce unpack_trees() time significantly (on webkit.git):
before after
--------------------------------------------------------------------
0.080394752 0.051258167 s: read cache .git/index
0.216010838 0.212106298 s: preload index
0.008534301 0.280521764 s: refresh index
0.251992198 0.218160442 s: traverse_trees
0.377031383 0.374948191 s: check_updates
0.372768105 0.037040114 s: cache_tree_update
1.045887251 0.672031609 s: unpack_trees
0.314983512 0.317456290 s: write index, changed mask = 2e
0.062572653 0.038382654 s: traverse_trees
0.000022544 0.000042731 s: check_updates
0.073795585 0.050930053 s: unpack_trees
0.073807557 0.051099735 s: diff-index
1.938191592 1.614241153 s: git command: git checkout -
[1] I'm pretty sure the reason is an oversight in 34110cd4e3 (Make
'unpack_trees()' have a separate source and destination index -
2008-03-06). That patch aims to _not_ update the source index at
all. The invalidation should have been done on o->result in that
patch. But then there was no cache-tree on o->result even then so
it's pointless to do so.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Performance measurements are listed right now as a flat list, which is
fine when we measure big blocks. But when we start adding more and
more measurements, some of them could be just part of a bigger
measurement and a flat list gives a wrong impression that they are
executed at the same level instead of nested.
Add trace_performance_enter() and trace_performance_leave() to allow
indent these nested measurements. For now it does not help much
because the only nested thing is (lazy) name hash initialization
(e.g. called in diff-index from "git status"). This will help more
because I'm going to add some more tracing that's actually nested.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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"git merge --abort" etc. did not clean things up properly when
there were conflicted entries in the index in certain order that
are involved in D/F conflicts. This has been corrected.
* en/abort-df-conflict-fixes:
read-cache: fix directory/file conflict handling in read_index_unmerged()
t1015: demonstrate directory/file conflict recovery failures
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Make the match_patchspec API and friends take an index_state instead
of assuming the_index in dir.c. All external call sites are converted
blindly to keep the patch simple and retain current behavior.
Individual call sites may receive further updates to use the right
index instead of the_index.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The recursive merge strategy did not properly ensure there was no
change between HEAD and the index before performing its operation,
which has been corrected.
* en/dirty-merge-fixes:
merge: fix misleading pre-merge check documentation
merge-recursive: enforce rule that index matches head before merging
t6044: add more testcases with staged changes before a merge is invoked
merge-recursive: fix assumption that head tree being merged is HEAD
merge-recursive: make sure when we say we abort that we actually abort
t6044: add a testcase for index matching head, when head doesn't match HEAD
t6044: verify that merges expected to abort actually abort
index_has_changes(): avoid assuming operating on the_index
read-cache.c: move index_has_changes() from merge.c
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For a large tree, the index needs to hold many cache entries
allocated on heap. These cache entries are now allocated out of a
dedicated memory pool to amortize malloc(3) overhead.
* jm/cache-entry-from-mem-pool:
block alloc: add validations around cache_entry lifecyle
block alloc: allocate cache entries from mem_pool
mem-pool: fill out functionality
mem-pool: add life cycle management functions
mem-pool: only search head block for available space
block alloc: add lifecycle APIs for cache_entry structs
read-cache: teach make_cache_entry to take object_id
read-cache: teach refresh_cache_entry to take istate
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read_index_unmerged() has two intended purposes:
* return 1 if there are any unmerged entries, 0 otherwise
* drops any higher-stage entries down to stage #0
There are several callers of read_index_unmerged() that check the return
value to see if it is non-zero, all of which then die() if that condition
is met. For these callers, dropping higher-stage entries down to stage #0
is a waste of resources, and returning immediately on first unmerged entry
would be better. But it's probably only a very minor difference and isn't
the focus of this series.
The remaining callers ignore the return value and call this function for
the side effect of dropping higher-stage entries down to stage #0. As
mentioned in commit e11d7b596970 ("'reset --merge': fix unmerged case",
2009-12-31),
The _only_ reason we want to keep a previously unmerged entry in the
index at stage #0 is so that we don't forget the fact that we have
corresponding file in the work tree in order to be able to remove it
when the tree we are resetting to does not have the path.
In fact, prior to commit d1a43f2aa4bf ("reset --hard/read-tree --reset -u:
remove unmerged new paths", 2008-10-15), read_index_unmerged() did just
remove unmerged entries from the cache immediately but that had the
unwanted effect of leaving around new untracked files in the tree from
aborted merges.
So, that's the intended purpose of this function. The problem is that
when directory/files conflicts are present, trying to add the file to the
index at stage 0 fails (because there is still a directory in the way),
and the function returns early with a -1 return code to signify the error.
As noted above, none of the callers who want the drop-to-stage-0 behavior
check the return status, though, so this means all remaining unmerged
entries remain in the index and the callers proceed assuming otherwise.
Users then see errors of the form:
error: 'DIR-OR-FILE' appears as both a file and as a directory
error: DIR-OR-FILE: cannot drop to stage #0
and potentially also messages about other unmerged entries which came
lexicographically later than whatever pathname was both a file and a
directory. Google finds a few hits searching for those messages,
suggesting there were probably a couple people who hit this besides me.
Luckily, calling `git reset --hard` multiple times would workaround
this bug.
Since the whole purpose here is to just put the entry *temporarily* into
the index so that any associated file in the working copy can be removed,
we can just skip the DFCHECK and allow both the file and directory to
appear in the index. The temporary simultaneous appearance of the
directory and file entries in the index will be removed by the callers
by calling unpack_trees(), which excludes these unmerged entries marked
with CE_CONFLICTED flag from the resulting index, before they attempt to
write the index anywhere.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The conversion to pass "the_repository" and then "a_repository"
throughout the object access API continues.
* sb/object-store-grafts:
commit: allow lookup_commit_graft to handle arbitrary repositories
commit: allow prepare_commit_graft to handle arbitrary repositories
shallow: migrate shallow information into the object parser
path.c: migrate global git_path_* to take a repository argument
cache: convert get_graft_file to handle arbitrary repositories
commit: convert read_graft_file to handle arbitrary repositories
commit: convert register_commit_graft to handle arbitrary repositories
commit: convert commit_graft_pos() to handle arbitrary repositories
shallow: add repository argument to is_repository_shallow
shallow: add repository argument to check_shallow_file_for_update
shallow: add repository argument to register_shallow
shallow: add repository argument to set_alternate_shallow_file
commit: add repository argument to lookup_commit_graft
commit: add repository argument to prepare_commit_graft
commit: add repository argument to read_graft_file
commit: add repository argument to register_commit_graft
commit: add repository argument to commit_graft_pos
object: move grafts to object parser
object-store: move object access functions to object-store.h
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`git merge-recursive` does a three-way merge between user-specified trees
base, head, and remote. Since the user is allowed to specify head, we can
not necesarily assume that head == HEAD.
Modify index_has_changes() to take an extra argument specifying the tree
to compare against. If NULL, it will compare to HEAD. We then use this
from merge-recursive to make sure we compare to the user-specified head.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Modify index_has_changes() to take a struct istate* instead of just
operating on the_index. This is only a partial conversion, though,
because we call do_diff_cache() which implicitly assumes work is to be
done on the_index. Ongoing work is being done elsewhere to do the
remainder of the conversion, and thus is not duplicated here. Instead,
a simple check is put in place until that work is complete.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Since index_has_change() is an index-related function, move it to
read-cache.c, only modifying it to avoid uses of the active_cache and
active_nr macros.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Add an option (controlled by an environment variable) perform extra
validations on mem_pool allocated cache entries. When set:
1) Invalidate cache_entry memory when discarding cache_entry.
2) When discarding index_state struct, verify that all cache_entries
were allocated from expected mem_pool.
3) When discarding mem_pools, invalidate mem_pool memory.
This should provide extra checks that mem_pools and their allocated
cache_entries are being used as expected.
Signed-off-by: Jameson Miller <jamill@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When reading large indexes from disk, a portion of the time is
dominated in malloc() calls. This can be mitigated by allocating a
large block of memory and manage it ourselves via memory pools.
This change moves the cache entry allocation to be on top of memory
pools.
Design:
The index_state struct will gain a notion of an associated memory_pool
from which cache_entries will be allocated from. When reading in the
index from disk, we have information on the number of entries and
their size, which can guide us in deciding how large our initial
memory allocation should be. When an index is discarded, the
associated memory_pool will be discarded as well - so the lifetime of
a cache_entry is tied to the lifetime of the index_state that it was
allocated for.
In the case of a Split Index, the following rules are followed. 1st,
some terminology is defined:
Terminology:
- 'the_index': represents the logical view of the index
- 'split_index': represents the "base" cache entries. Read from the
split index file.
'the_index' can reference a single split_index, as well as
cache_entries from the split_index. `the_index` will be discarded
before the `split_index` is. This means that when we are allocating
cache_entries in the presence of a split index, we need to allocate
the entries from the `split_index`'s memory pool. This allows us to
follow the pattern that `the_index` can reference cache_entries from
the `split_index`, and that the cache_entries will not be freed while
they are still being referenced.
Managing transient cache_entry structs:
Cache entries are usually allocated for an index, but this is not always
the case. Cache entries are sometimes allocated because this is the
type that the existing checkout_entry function works with. Because of
this, the existing code needs to handle cache entries associated with an
index / memory pool, and those that only exist transiently. Several
strategies were contemplated around how to handle this:
Chosen approach:
An extra field was added to the cache_entry type to track whether the
cache_entry was allocated from a memory pool or not. This is currently
an int field, as there are no more available bits in the existing
ce_flags bit field. If / when more bits are needed, this new field can
be turned into a proper bit field.
Alternatives:
1) Do not include any information about how the cache_entry was
allocated. Calling code would be responsible for tracking whether the
cache_entry needed to be freed or not.
Pro: No extra memory overhead to track this state
Con: Extra complexity in callers to handle this correctly.
The extra complexity and burden to not regress this behavior in the
future was more than we wanted.
2) cache_entry would gain knowledge about which mem_pool allocated it
Pro: Could (potentially) do extra logic to know when a mem_pool no
longer had references to any cache_entry
Con: cache_entry would grow heavier by a pointer, instead of int
We didn't see a tangible benefit to this approach
3) Do not add any extra information to a cache_entry, but when freeing a
cache entry, check if the memory exists in a region managed by existing
mem_pools.
Pro: No extra memory overhead to track state
Con: Extra computation is performed when freeing cache entries
We decided tracking and iterating over known memory pool regions was
less desirable than adding an extra field to track this stae.
Signed-off-by: Jameson Miller <jamill@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Junio C Hamano
Jonathan Nieder
Ævar Arnfjörð Bjarmason
Nguyễn Thái Ngọc Duy
Ben Peart
Carlo Marcelo Arenas Belón
SZEDER Gábor
Jeff King
Elijah Newren
Jameson Miller