Two functions, namely write_idx_file() and open_pack_file(), currently
return a const pointer. However that pointer is either a copy of the
first argument, or set to a malloc'd buffer when that first argument
is null. In the later case it is wrong to qualify that pointer as const
since ownership of the buffer is transferred to the caller to dispose of,
and obviously the free() function is not meant to be passed const
pointers.
Making the return pointer not const causes a warning when the first
argument is returned since that argument is also marked const.
The correct thing to do is therefore to remove the const qualifiers,
avoiding the need for ugly casts only to silence some warnings.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
To keep things well layered, sha1close() now returns the file descriptor
when it doesn't close the file.
An ugly cast was added to the return of write_idx_file() to avoid a
warning. A proper fix will come separately.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
... so don't even try in that case, and save another useless line of
progress display.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Each progress can be on a single line instead of two.
[sp: Changed "Checking files out" to "Checking out files" at
Johannes Sixt's suggestion as it better explains the
action that is taking place]
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
* jc/autogc:
git-gc --auto: run "repack -A -d -l" as necessary.
git-gc --auto: restructure the way "repack" command line is built.
git-gc --auto: protect ourselves from accumulated cruft
git-gc --auto: add documentation.
git-gc --auto: move threshold check to need_to_gc() function.
repack -A -d: use --keep-unreachable when repacking
pack-objects --keep-unreachable
Export matches_pack_name() and fix its return value
Invoke "git gc --auto" from commit, merge, am and rebase.
Implement git gc --auto
This new option is meant to be used in conjunction with the
options "git repack -a -d" usually invokes the underlying
pack-objects with. When this option is given, objects unreachable
from the refs in packs named with --unpacked= option are added
to the resulting pack, in addition to the reachable objects that
are not in packs marked with *.keep files.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This adds a --threads=<n> parameter to 'git pack-objects' with
documentation.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Try to keep object with the same name hash together.
Suggested by Martin Koegler.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
With this, each thread get repeatedly assigned the next available chunk of
objects to process until the whole list is done. The idea is to have
reasonably small chunks so that all CPUs remain busy with a minimum
number of threads for as long as there is data to process.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
this is still rough, hence it is disabled by default. You need to compile
with "make THREADED_DELTA_SEARCH=1 ..." at the moment.
Threading is done on different portions of the object list to be
deltified. This is currently done by spliting the list into n parts and
then a thread is spawned for each of them. A better method would consist
of spliting the list into more smaller parts and have the n threads
pick the next part available.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This is to help threadification of the delta search code, with a bonus
consistency check.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Not all objects are subject to deltification, so avoid carrying those
along, and provide the real count to progress display.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This is based on Martin Koegler's idea to keep the object that
was successfully used as the base of the delta when it is about
to fall off the edge of the window. Instead of doing so only
for the objects at the edge of the window, this makes the window
a lru eviction mechanism. If an entry is used as a base, it is
moved to the last of the queue to be evicted.
This is a quick-and-dirty implementation, as it keeps the original
implementation of the data structure used for the window. This
originally was done as an array, not as an array of pointers,
because it was meant to be used as a cyclic FIFO buffer and a
plain array avoids an extra pointer indirection, while its FIFOness
eant that we are not "moving" the entries like this patch does.
The runtime from three versions were comparable. It seems to
make the resulting chain even shorter, which can only be good.
(stock "master") 15782196 bytes
chain length = 1: 2972 objects
chain length = 2: 2651 objects
chain length = 3: 2369 objects
chain length = 4: 2121 objects
chain length = 5: 1877 objects
...
chain length = 46: 490 objects
chain length = 47: 515 objects
chain length = 48: 527 objects
chain length = 49: 570 objects
chain length = 50: 408 objects
(with your patch) 15745736 bytes (0.23% smaller)
chain length = 1: 3137 objects
chain length = 2: 2688 objects
chain length = 3: 2322 objects
chain length = 4: 2146 objects
chain length = 5: 1824 objects
...
chain length = 46: 503 objects
chain length = 47: 509 objects
chain length = 48: 536 objects
chain length = 49: 588 objects
chain length = 50: 357 objects
(with this patch) 15612086 bytes (1.08% smaller)
chain length = 1: 4831 objects
chain length = 2: 3811 objects
chain length = 3: 2964 objects
chain length = 4: 2352 objects
chain length = 5: 1944 objects
...
chain length = 46: 327 objects
chain length = 47: 353 objects
chain length = 48: 304 objects
chain length = 49: 298 objects
chain length = 50: 135 objects
[jc: this is with code simplification follow-up from Nico]
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The code favoring shallower deltas when size is equal was triggered
only when previous delta was also cached. There should be no relation
between cached deltas and same sized deltas.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When a thin pack wants to send a tree object at "sub/dir", and
the commit that is common between the sender and the receiver
that is used as the base object has a subproject at that path,
we should not try to use the data at "sub/dir" of the base tree
as a tree object. It is not a tree to begin with, and more
importantly, the commit object there does not have to even
exist.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Not only are they unused, but the order in the function declaration
and the actual usage don't match.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
xmkstemp() performs error checking and prints a standard error message when
an error occur.
Signed-off-by: Luiz Fernando N. Capitulino <lcapitulino@mandriva.com.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Commit 5a235b5e was missing this little detail. Otherwise your pack
will explode.
Problem noted by Brian Downing.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The delta depth doesn't have to be stored in the global object array
structure since it is only used during the deltification pass.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This adds an option (--window-memory=N) and configuration variable
(pack.windowMemory = N) to limit the memory size of the pack-objects
delta search window. This works by removing the oldest unpacked objects
whenever the total size goes above the limit. It will always leave
at least one object, though, so as not to completely eliminate the
possibility of computing deltas.
This is an extra limit on top of the normal window size (--window=N);
the window will not dynamically grow above the fixed number of entries
specified to fill the memory limit.
With this, repacking a repository with a mix of large and small objects
is possible even with a very large window.
Cleaner and correct circular buffer handling courtesy of Nicolas Pitre.
Signed-off-by: Brian Downing <bdowning@lavos.net>
Acked-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a new try_delta heuristic. Don't bother trying to make a delta if
the target object size is much smaller (currently 1/32) than the source,
as it's very likely not going to get a match. Even if it does, you will
have to read at least 32x the size of the new file to reassemble it,
which isn't such a good deal. This leads to a considerable performance
improvement when deltifying a mix of small and large files with a very
large window, because you don't have to wait for the large files to
percolate out of the window before things start going fast again.
Signed-off-by: Brian Downing <bdowning@lavos.net>
Acked-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We already apply a bias on the initial delta attempt with max_size being
a function of the base object depth. This has the effect of favoring
shallower deltas even if deeper deltas could be smaller, and therefore
creating a wider delta tree (see commits 4e8da195 and c3b06a69).
This principle should also be applied to all delta attempts for the same
object and not only the first attempt. With this the criteria for the
best delta is not only its size but also its depth, so that a shallower
delta might be selected even if it is larger than a deeper one. Even if
some deltas get larger, they allow for wider delta trees making the
depth limit less quickly reached and therefore better deltas can be
subsequently found, keeping the resulting pack size even smaller.
Runtime access to the pack should also benefit from shallower deltas.
Testing on different repositories showed slighter faster repacks,
smaller resulting packs, and a much nicer curve for delta depth
distribution with no more peak at the maximum depth level.
Improvements are even more significant with smaller depth limits.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Change "try_delta" so that if it finds a delta that has the same size
but shallower depth than the existing delta, it will prefer the
shallower one. This makes certain delta trees vastly less deep.
Signed-off-by: Brian Downing <bdowning@lavos.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This uses "git-apply --whitespace=strip" to fix whitespace errors that have
crept in to our source files over time. There are a few files that need
to have trailing whitespaces (most notably, test vectors). The results
still passes the test, and build result in Documentation/ area is unchanged.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This patch unifies the write_index_file functions in
builtin-pack-objects.c and index-pack.c. As the name
"index" is overloaded in git, move in the direction of
using "idx" and "pack idx" when refering to the pack index.
There should be no change in functionality.
Signed-off-by: Geert Bosch <bosch@gnat.com>
Acked-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Two issues here:
1) git-repack -a --max-pack-size=10 on the GIT repo dies pretty quick.
There is a lot of confusion about deltas that were suposed to be
reused from another pack but that get stored undeltified due to pack
limit and object size doesn't match entry->size anymore. This test
is not really worth the complexity for determining when it is valid
so get rid of it.
2) If pack limit is reached, the object buffer is freed, including when
it comes from a cached delta data. In practice the object will be
stored in a subsequent pack undeltified, but let's make sure no
pointer to freed data subsists by clearing entry->delta_data.
I also reorganized that code a bit to make it more readable.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Creating deltas between big blobs is a CPU and memory intensive task.
In the writing phase, all (not reused) deltas are redone.
This patch adds support for caching deltas from the deltifing phase, so
that that the writing phase is faster.
The caching is limited to small deltas to avoid increasing memory usage very much.
The implemented limit is (memory needed to create the delta)/1024.
Signed-off-by: Martin Koegler <mkoegler@auto.tuwien.ac.at>
Signed-off-by: Junio C Hamano <junkio@cox.net>
If builtin-pack-objects runs out of memory while finding
the best deltas, it bails out with an error.
If the delta index creation fails (because there is not enough memory),
we can downgrade the error message to a warning and continue with the
next object.
Signed-off-by: Martin Koegler <mkoegler@auto.tuwien.ac.at>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Explain the special code for detecting a corner-case error,
and complain about --stdout & --max-pack-size being used together.
Signed-off-by: Dana L. How <danahow@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
As we do not consider objects marked as "no-delta" early, there
is no point to check if the other objects already in the delta
window are marked as such -- "no-delta" objects will not enter
the window to begin with.
Pointed out by Nico.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This teaches pack-objects to use .gitattributes mechanism so
that the user can specify certain blobs are not worth spending
CPU cycles to attempt deltification.
The name of the attrbute is "delta", and when it is set to
false, like this:
== .gitattributes ==
*.jpg -delta
they are always stored in the plain-compressed base object
representation.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Instead of giving a hash for grouping, pass fullname to add_object_entry().
I want to add "do not try deltifying this object" bit to object_entry based on
the settings in .gitattributes, and hashing the name down too early would
interfere with that plan.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Add --max-pack-size parsing and usage messages.
Upgrade git-repack.sh to handle multiple packfile names,
and build packfiles in GIT_OBJECT_DIRECTORY not GIT_DIR.
Update documentation.
Signed-off-by: Dana L. How <danahow@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Rewrite write_pack_file() to break to a new packfile
whenever write_object/write_one request it, and
correct the header's object count in the previous packfile.
Change write_index_file() to write an index
for just the objects in the most recent packfile.
Signed-off-by: Dana L. How <danahow@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
With --max-pack-size, generate the appropriate write limit
for each object and check against it before each group of writes.
Update delta usability rules to handle base being in a previously-
written pack. Inline sha1write_compress() so we know the
exact size of the written data when it needs to be compressed.
Detect and return write "failure".
Signed-off-by: Dana L. How <danahow@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Add "pack_size_limit", the limit specified by --max-pack-size,
"written_list", the list of objects written to the current pack,
and "nr_written", the number of objects in written_list.
Put "base_name" at file scope again and add forward declarations.
Move write_index_file() call from cnd_pack_objects() to
write_pack_file() since only the latter will know how
many times to call write_index_file().
Signed-off-by: Dana L. How <danahow@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Add config variables pack.compression and core.loosecompression ,
and switch --compression=level to pack-objects.
Loose objects will be compressed using core.loosecompression if set,
else core.compression if set, else Z_BEST_SPEED.
Packed objects will be compressed using --compression=level if seen,
else pack.compression if set, else core.compression if set,
else Z_DEFAULT_COMPRESSION. This is the "pack compression level".
Loose objects added to a pack undeltified will be recompressed
to the pack compression level if it is unequal to the current
loose compression level by the preceding rules, or if the loose
object was written while core.legacyheaders = true. Newly
deltified loose objects are always compressed to the current
pack compression level.
Previously packed objects added to a pack are recompressed
to the current pack compression level exactly when their
deltification status changes, since the previous pack data
cannot be reused.
In either case, the --no-reuse-object switch from the first
patch below will always force recompression to the current pack
compression level, instead of assuming the pack compression level
hasn't changed and pack data can be reused when possible.
This applies on top of the following patches from Nicolas Pitre:
[PATCH] allow for undeltified objects not to be reused
[PATCH] make "repack -f" imply "pack-objects --no-reuse-object"
Signed-off-by: Dana L. How <danahow@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Now that we encourage and actively preserve objects in a packed form
more agressively than we did at the time the new loose object format and
core.legacyheaders were introduced, that extra loose object format
doesn't appear to be worth it anymore.
Because the packing of loose objects has to go through the delta match
loop anyway, and since most of them should end up being deltified in
most cases, there is really little advantage to have this parallel loose
object format as the CPU savings it might provide is rather lost in the
noise in the end.
This patch gets rid of core.legacyheaders, preserve the legacy format as
the only writable loose object format and deprecate the other one to
keep things simpler.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Currently non deltified object data is always reused when possible.
This means that any change to core.compression has no effect on those
objects as they don't get recompressed when repacking them.
Let's add a --no-reuse-object flag to git-repack in order to force
recompression of all objects when desired.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
If the progress bar ends up in a box, better provide a title for it too.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Instead of having this code duplicated in multiple places, let's have
a common interface for progress display. If someday someone wishes to
display a cheezy progress bar instead then only one file will have to
be changed.
Note: I left merge-recursive.c out since it has a strange notion of
progress as it apparently increase the expected total number as it goes.
Someone with more intimate knowledge of what that is supposed to mean
might look at converting it to the common progress interface.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
The earlier quickfix forced world-readable permission bits. This
updates it to honor umask and core.sharedrepository settings.
Signed-off-by: Junio C Hamano <junkio@cox.net>
mkstemp() often creates the file in 0600 which means the
resulting packfile is not readable by anybody other than the
repository owner. Force 0644 for now, even though this is not
strictly correct.
Signed-off-by: Junio C Hamano <junkio@cox.net>
With large amount of objects, check_object() is really trashing the pack
sliding map and the filesystem cache. It has a completely random access
pattern especially with old objects where delta replay jumps back and
forth all over the pack.
This patch improves things by:
1) sorting objects by their offset in pack before calling check_object()
so the pack access pattern is linear;
2) recording the object type at add_object_entry() time since it is
already known in most cases;
3) recording the pack offset even for preferred_base objects;
4) avoid calling sha1_object_info() if all possible.
This limits pack accesses to the bare minimum and makes them perfectly
linear.
In the process check_object() was made more clear (to me at least).
Note: I thought about walking the sorted_by_offset list backward in
get_object_details() so if a pack happens to be larger than the available
file cache, then the cache would have been populated with useful data from
the beginning of the pack already when find_deltas() is called. Strangely,
testing (on Linux) showed absolutely no performance difference.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
It currently aliases delta_size on the principle that reused deltas won't
go through the whole delta matching loop hence delta_size was unused.
This is not true if given delta doesn't find its base in the pack though.
But we need that information even for whole object data reuse.
Well in short the current state looks awful and is prone to bugs. It just
works fine now because try_delta() tests trg_entry->delta before using
trg_entry->delta_size, but that is a bit subtle and I was wondering for a
while why things just worked fine... even if I'm guilty of having
introduced this abomination myself in the first place.
Let's do the sensible thing instead with no ambiguity, which is to have
a separate variable for in_pack_header_size. This might even help future
optimizations.
While at it, let's reorder some struct object_entry members so they all
align well with their own width, regardless of the architecture or the
size of off_t. Some memory saving is to be expected with this alone.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Because we don't have to know the SHA1 h(hence the name) of the pack
up front anymore, let's get rid of yet another global sorted object list
and sort them only in write_index_file(), then compute the object list
SHA1 on the fly.
This has the advantage of saving another chunk of memory, and the sorted
list SHA1 won't be computed needlessly on servers during a fetch.
Of course the cunning plan is also to make write_index_file() much like
the function with the same name in index-pack.c for an eventual easy
sharing.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This capability is practically never useful, and therefore never tested,
because it is fairly unlikely that the requested pack will be already
available. Furthermore it is of little gain over the ability to reuse
existing pack data.
In fact the ability to change delta type on the fly when reusing delta
data is a nice thing that has almost no cost and allows greater backward
compatibility with a client's capabilities than if the client is blindly
sent a whole pack without any discrimination.
And this "feature" is simply in the way of other cleanups.
Let's get rid of it.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Get rid of sort_comparator() as it impose a run time double indirect
function call for little compile time type checking gain.
Also get rid of create_sorted_list() as it only has one user which would
as well be just fine doing its sorting locally. Eventually the list of
deltifiable objects might be shorter than the whole object list.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Objects that have delta "children" from pack data reuse must consider the
depth of their deepest child when they try to deltify themselves for those
children not to become too deep.
However, in the context of a "thin" pack, the delta children depth was
skipped entirely on the presumption that the pack was always going to be
exploded on the receiving end, hence the delta length wasn't an issue.
Now that we keep received packs as is and reuse pack data when repacking,
those packs do contain delta chains that are longer than expected. Worse,
those delta chain may even grow longer when the pack is further repacked
into another thin pack for a subsequent transmission.
So this patch restores strict delta length even for thin packs, and it
moves check_delta_limit() usage directly in the delta loop where it is
needed. This way the delta_limit can be removed from struct object_entry
as well. Oh and the initial value was wrong too.
The progress_interval() function was moved to a more logical location in
the process.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Before finding best delta combinations, we sort objects by name hash,
then by size, then by their position in memory. Then we walk the list
backwards to test delta candidates.
We hope that a bigger size usually means a newer objects. But a bigger
address in memory does not mean a newer object. So the last comparison
must be reversed.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Let's avoid some cycles when there is no base to test against, and avoid
unnecessary object lookups.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This function used to call locate_object_entry_hash() _twice_ per added
object while only once should suffice. Let's reorganize that code a bit.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This replaces the inflate validation with a CRC validation when reusing
data from a pack which uses index version 2. That makes repacking much
safer against corruptions, and it should be a bit faster too.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This is necessary for testing the new capabilities in some automated
way without having an actual 4GB+ pack.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Pack index version 2 goes as follows:
- 8 bytes of header with signature and version.
- 256 entries of 4-byte first-level fan-out table.
- Table of sorted 20-byte SHA1 records for each object in pack.
- Table of 4-byte CRC32 entries for raw pack object data.
- Table of 4-byte offset entries for objects in the pack if offset is
representable with 31 bits or less, otherwise it is an index in the next
table with top bit set.
- Table of 8-byte offset entries indexed from previous table for offsets
which are 32 bits or more (optional).
- 20-byte SHA1 checksum of sorted object names.
- 20-byte SHA1 checksum of the above.
The object SHA1 table is all contiguous so future pack format that would
contain this table directly won't require big changes to the code. It is
also tighter for slightly better cache locality when looking up entries.
Support for large packs exceeding 31 bits in size won't impose an index
size bloat for packs within that range that don't need a 64-bit offset.
And because newer objects which are likely to be the most frequently used
are located at the beginning of the pack, they won't pay the 64-bit offset
lookup at run time either even if the pack is large.
Right now an index version 2 is created only when the biggest offset in a
pack reaches 31 bits. It might be a good idea to always use index version
2 eventually to benefit from the CRC32 it contains when reusing pack data
while repacking.
[jc: with the "oops" fix to keep track of the last offset correctly]
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
The most important optimization for performance when repacking is the
ability to reuse data from a previous pack as is and bypass any delta
or even SHA1 computation by simply copying the raw data from one pack
to another directly.
The problem with this is that any data corruption within a copied object
would go unnoticed and the new (repacked) pack would be self-consistent
with its own checksum despite containing a corrupted object. This is a
real issue that already happened at least once in the past.
In some attempt to prevent this, we validate the copied data by inflating
it and making sure no error is signaled by zlib. But this is still not
perfect as a significant portion of a pack content is made of object
headers and references to delta base objects which are not deflated and
therefore not validated when repacking actually making the pack data reuse
still not as safe as it could be.
Of course a full SHA1 validation could be performed, but that implies
full data inflating and delta replaying which is extremely costly, which
cost the data reuse optimization was designed to avoid in the first place.
So the best solution to this is simply to store a CRC32 of the raw pack
data for each object in the pack index. This way any object in a pack can
be validated before being copied as is in another pack, including header
and any other non deflated data.
Why CRC32 instead of a faster checksum like Adler32? Quoting Wikipedia:
Jonathan Stone discovered in 2001 that Adler-32 has a weakness for very
short messages. He wrote "Briefly, the problem is that, for very short
packets, Adler32 is guaranteed to give poor coverage of the available
bits. Don't take my word for it, ask Mark Adler. :-)" The problem is
that sum A does not wrap for short messages. The maximum value of A for
a 128-byte message is 32640, which is below the value 65521 used by the
modulo operation. An extended explanation can be found in RFC 3309,
which mandates the use of CRC32 instead of Adler-32 for SCTP, the
Stream Control Transmission Protocol.
In the context of a GIT pack, we have lots of small objects, especially
deltas, which are likely to be quite small and in a size range for which
Adler32 is dimed not to be sufficient. Another advantage of CRC32 is the
possibility for recovery from certain types of small corruptions like
single bit errors which are the most probable type of corruptions.
OK what this patch does is to compute the CRC32 of each object written to
a pack within pack-objects. It is not written to the index yet and it is
obviously not validated when reusing pack data yet either.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Change a few size and offset variables to more appropriate type, then
add overflow tests on those offsets. This prevents any bad data to be
generated/processed if off_t happens to not be large enough to handle
some big packs.
Better be safe than sorry.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This patch introduces the MSB() macro to obtain the desired number of
most significant bits from a given variable independently of the variable
type.
It is then used to better implement the overflow test on the OBJ_OFS_DELTA
base offset variable with the property of always working correctly
regardless of the type/size of that variable.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
The coming index format change doesn't allow for the number of objects
to be determined from the size of the index file directly. Instead, Let's
initialize a field in the packed_git structure with the object count when
the index is validated since the count is always known at that point.
While at it let's reorder some struct packed_git fields to avoid padding
due to needed 64-bit alignment for some of them.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Let's avoid the open coded pack index reference in pack-object and use
nth_packed_object_sha1() instead. This will help encapsulating index
format differences in one place.
And while at it there is no reason to copy SHA1's over and over while a
direct pointer to it in the index will do just fine.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Acked-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This removes slightly more lines than it adds, but the real reason for
doing this is that future optimizations will require more setup of the
tree descriptor, and so we want to do it in one place.
Also renamed the "desc.buf" field to "desc.buffer" just to trigger
compiler errors for old-style manual initializations, making sure I
didn't miss anything.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Since we have the "tree_entry_len()" helper function these days, and
don't need to do a full strlen(), there's no point in saving the path
length - it's just redundant information.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Especially with the new index format to come, it is more appropriate
to encapsulate more into check_packed_git_idx() and assume less of the
index format in struct packed_git.
To that effect, the index_base is renamed to index_data with void * type
so it is not used directly but other pointers initialized with it. This
allows for a couple pointer cast removal, as well as providing a better
generic name to grep for when adding support for new index versions or
formats.
And index_data is declared const too while at it.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Always use an off_t value in pack-objects anytime we are dealing
with an offset to some data within a packfile.
Also fixed a minor uintmax_t that was incorrectly defined before.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
As we technically try to support up to a maximum of 2**32-1 objects
in a single packfile we should act like it and use unsigned 32 bit
integers for all of our object counts and progress output.
This change does not modify everything in pack-objects that probably
needs to change to fully support the maximum of 2**32-1 objects.
I'm intentionally breaking the improvements into slightly smaller
commits to make them easier to follow.
No logic change should be occuring here, with the exception that
some comparsions will now work properly when the number of objects
exceeds 2**31-1.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
We currently have two parallel notation for dealing with object types
in the code: a string and a numerical value. One of them is obviously
redundent, and the most used one requires more stack space and a bunch
of strcmp() all over the place.
This is an initial step for the removal of the version using a char array
found in object reading code paths. The patch is unfortunately large but
there is no sane way to split it in smaller parts without breaking the
system.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Sometime typename() is used, sometimes type_names[] is accessed directly.
Let's enforce typename() all the time which allows for validating the
type.
Also let's add a function to go from a name to a type and use it instead
of manual memcpy() when appropriate.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
* maint:
Add Release Notes to prepare for 1.5.0.2
Allow arbitrary number of arguments to git-pack-objects
rerere: do not deal with symlinks.
rerere: do not skip two conflicted paths next to each other.
Don't modify CREDITS-FILE if it hasn't changed.
If a repository ever gets in a situation where there are too many
packs (more than 60 or so), perhaps because of frequent use of
git-fetch -k or incremental git-repack, then it becomes impossible to
fully repack the repository with git-repack -a. That command just
dies with the cryptic message
fatal: too many internal rev-list options
This message comes from git-pack-objects, which is passed one command
line option like --unpacked=pack-<SHA1>.pack for each pack file to be
repacked. However, the current code has a static limit of 64 command
line arguments and just aborts if more arguments are passed to it.
Fix this by dynamically allocating the array of command line
arguments, and doubling the size each time it overflows.
Signed-off-by: Roland Dreier <roland@digitalvampire.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Previous step converted use of strncmp() with literal string
mechanically even when the result is only used as a boolean:
if (!strncmp("foo", arg, 3)) ==> if (!(-prefixcmp(arg, "foo")))
This step manually cleans them up to read:
if (!prefixcmp(arg, "foo"))
Signed-off-by: Junio C Hamano <junkio@cox.net>
This mechanically converts strncmp() to use prefixcmp(), but only when
the parameters match specific patterns, so that they can be verified
easily. Leftover from this will be fixed in a separate step, including
idiotic conversions like
if (!strncmp("foo", arg, 3))
=>
if (!(-prefixcmp(arg, "foo")))
This was done by using this script in px.perl
#!/usr/bin/perl -i.bak -p
if (/strncmp\(([^,]+), "([^\\"]*)", (\d+)\)/ && (length($2) == $3)) {
s|strncmp\(([^,]+), "([^\\"]*)", (\d+)\)|prefixcmp($1, "$2")|;
}
if (/strncmp\("([^\\"]*)", ([^,]+), (\d+)\)/ && (length($1) == $3)) {
s|strncmp\("([^\\"]*)", ([^,]+), (\d+)\)|(-prefixcmp($2, "$1"))|;
}
and running:
$ git grep -l strncmp -- '*.c' | xargs perl px.perl
Signed-off-by: Junio C Hamano <junkio@cox.net>
The code calls use_pack() to make that the variably encoded
offset fits in the mmap'ed window, but it forgot that the
operation gives the pointer to the beginning of the asked
region.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Junio noticed that 'non-trivial' pushes were failing if executed
using the sliding window mmap changes. This was somewhat difficult
to track down as the failure was appearing randomly.
It turns out this was a failure caused by the delta base reference
(either ref or offset format) spanning over the end of a mmap window.
The error in pack-objects was we were not recalling use_pack
after the object header was unpacked, and therefore we did not
get the promise of at least 20 bytes in the buffer for the delta
base parsing. This would case later memcmp() calls to walk into
unassigned address space at the end of the window.
The reason Junio and I had hard time tracking this down in current
Git repositories is we were both probably packing with offset deltas,
which minimized the odds of the delta base reference spanning over
the end of the mmap window. Stepping back and repacking with
version 1.3.3 (which only supported reference deltas) increased
the likelyhood of seeing the bug.
The correct technique (as used in sha1_file.c) is to invoke
use_pack() after unpack_object_header_gently to ensure we have
enough data available for the delta base decoding.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
When multiple mmaps start getting used for all pack file access it
is not possible to get all data associated with a specific object
in one contiguous memory region. This limitation prevents simply
passing a single address and length to SHA1_Update or to inflate.
Instead we need to loop until we have processed all data of interest.
As we loop over the data we are always interested in reusing the same
window 'cursor', as the prior window will no longer be of any use
to us. This allows the use_pack() call to automatically decrement
the use count of the prior window before setting up access for us
to the next window.
Within each loop we need to make use of the available length output
parameter of use_pack() to tell us how many bytes are available in
the current memory region, as we cannot tell otherwise.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Part of the implementation concept of the sliding mmap window for
pack access is to permit multiple windows per pack to be mapped
independently. Since the inuse_cnt is associated with the mmap and
not with the file, this value is in struct pack_window and needs to
be incremented/decremented for each pack_window accessed by any code.
To faciliate that implementation we need to replace all uses of
use_packed_git() and unuse_packed_git() with a different API that
follows struct pack_window objects rather than struct packed_git.
The way this works is when we need to start accessing a pack for
the first time we should setup a new window 'cursor' by declaring
a local and setting it to NULL:
struct pack_windows *w_curs = NULL;
To obtain the memory region which contains a specific section of
the pack file we invoke use_pack(), supplying the address of our
current window cursor:
unsigned int len;
unsigned char *addr = use_pack(p, &w_curs, offset, &len);
the returned address `addr` will be the first byte at `offset`
within the pack file. The optional variable len will also be
updated with the number of bytes remaining following the address.
Multiple calls to use_pack() with the same window cursor will
update the window cursor, moving it from one window to another
when necessary. In this way each window cursor variable maintains
only one struct pack_window inuse at a time.
Finally before exiting the scope which originally declared the window
cursor we must invoke unuse_pack() to unuse the current window (which
may be different from the one that was first obtained from use_pack):
unuse_pack(&w_curs);
This implementation is still not complete with regards to multiple
windows, as only one window per pack file is supported right now.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
The idea behind the sliding mmap window pack reader implementation
is to have multiple mmap regions active against the same pack file,
thereby allowing the process to mmap in only the active/hot sections
of the pack and reduce overall virtual address space usage.
To implement this we need to refactor the mmap related data
(pack_base, pack_use_cnt) out of struct packed_git and move them
into a new struct pack_window.
We are refactoring the code to support a single struct pack_window
per packfile, thereby emulating the prior behavior of mmap'ing the
entire pack file.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This adds a new option --reflog to pack-objects and revision
machinery; do not bother documenting it for now, since this is
only useful for local repacking.
When the option is passed, objects reachable from reflog entries
are marked as interesting while computing the set of objects to
pack.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This is a mechanical clean-up of the way *.c files include
system header files.
(1) sources under compat/, platform sha-1 implementations, and
xdelta code are exempt from the following rules;
(2) the first #include must be "git-compat-util.h" or one of
our own header file that includes it first (e.g. config.h,
builtin.h, pkt-line.h);
(3) system headers that are included in "git-compat-util.h"
need not be included in individual C source files.
(4) "git-compat-util.h" does not have to include subsystem
specific header files (e.g. expat.h).
Signed-off-by: Junio C Hamano <junkio@cox.net>
The final 'nr_result' and 'written' values must always be the same
otherwise we're in deep trouble. So let's remove a redundent report.
And for paranoia sake let's make sure those two variables are actually
equal after all objects are written (one never knows).
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
The heuristics to give up deltification when both the source and the
target are both in the same pack affects negatively when we are
repacking the subset of objects in the existing pack. This caused
any incremental updates to use suboptimal packs. Tweak the heuristics
to avoid this problem.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This adds documentation for --progress and --all-progress, remove a
duplicate --progress handling and make usage string more readable.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Currently git-push displays progress status for the local packing of
objects to send, but nothing once it starts to push it over the
connection. Having progress status in that later case is especially
nice when pushing lots of objects over a slow network link.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
