Copying the first bytes of a SHA1 is duplicated in six places,
however, the implications (the actual value would depend on the
endianness of the platform) is documented only once.
Add a properly documented API for this.
Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Whenever the hash table becomes too small then its size is increased,
the original part (and the added space) is zerod out using memset(),
and the table is rebuilt from scratch.
Simplify this proceess by returning the old memory using free() and
allocating the new buffer using xcalloc(), which already clears the
buffer for us. That way we avoid copying the old hash table contents
needlessly inside xrealloc().
While at it, use the first array member with sizeof instead of a
specific type. The old code used uint32_t and int, while index is
actually an array of int32_t. Their sizes are the same basically
everywhere, so it's not actually a problem, but the new code is
cleaner and doesn't have to be touched should the type be changed.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The hash table that stores the packing list for a given `pack-objects`
run was tightly coupled to the pack-objects code.
In this commit, we refactor the hash table and the underlying storage
array into a `packing_data` struct. The functionality for accessing and
adding entries to the packing list is hence accessible from other parts
of Git besides the `pack-objects` builtin.
This refactoring is a requirement for further patches in this series
that will require accessing the commit packing list from outside of
`pack-objects`.
The hash table implementation has been minimally altered: we now
use table sizes which are always a power of two, to ensure a uniform
index distribution in the array.
Signed-off-by: Vicent Marti <tanoku@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When packing an object without deltifying, if the data is stored in
a loose object that is encoded with a new style header, copy it without
inflating and deflating.
Signed-off-by: Junio C Hamano <junkio@cox.net>
For some repositories, deltas simply don't make sense. One can disable
them for git-repack by adding --window, but git-push insists on making
the deltas which can be very CPU-intensive for little benefit.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>
The only visible change is that git-blame doesn't understand
"--compability" anymore, but it does accept "--compatibility" instead,
which is already documented.
Signed-off-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
If no delta is attempted on some objects then it is useless to load them
in memory, neither create any delta index for them. The best thing to
do is therefore to load and index them only when really needed.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Without this there would never be a chance to improve packing for
previously undeltified objects.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
In the repacking window, if both objects we are looking at already came
from the same (old) pack-file, don't bother delta'ing them against each
other.
That means that we'll still always check for better deltas for (and
against!) _unpacked_ objects, but assuming incremental repacks, you'll
avoid the delta creation 99% of the time.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This does not implement sideband for propagating the status to
the downloader yet, but add code to capture the standard error
output from the pack-objects process in preparation for sending
it off to the client when the protocol extension allows us to do
so.
Signed-off-by: Junio C Hamano <junkio@cox.net>
ANSI C99 doesn't allow void-pointer arithmetic. This patch fixes this in
various ways. Usually the strategy that required the least changes was used.
Signed-off-by: Florian Forster <octo@verplant.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This trivial patch not only simplifies the name hashing, it actually
improves packing for both git and the kernel.
The git archive pack shrinks from 6824090->6622627 bytes (a 3%
improvement), and the kernel pack shrinks from 108756213 to 108219021 (a
mere 0.5% improvement, but still, it's an improvement from making the
hashing much simpler!)
We just create a 32-bit hash, where we "age" previous characters by two
bits, so the last characters in a filename count most. So when we then
compare the hashes in the sort routine, filenames that end the same way
sort the same way.
It takes the subdirectory into account (unless the filename is > 16
characters), but files with the same name within the same subdirectory
will obviously sort closer than files in different subdirectories.
And, incidentally (which is why I tried the hash change in the first
place, of course) builtin-rev-list.c will sort fairly close to rev-list.c.
And no, it's not a "good hash" in the sense of being secure or unique, but
that's not what we're looking for. The whole "hash" thing is misnamed
here. It's not so much a hash as a "sorting number".
[jc: rolled in simplification for computing the sorting number
computation for thin pack base objects]
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This adds a "tree_entry()" function that combines the common operation of
doing a "tree_entry_extract()" + "update_tree_entry()".
It also has a simplified calling convention, designed for simple loops
that traverse over a whole tree: the arguments are pointers to the tree
descriptor and a name_entry structure to fill in, and it returns a boolean
"true" if there was an entry left to be gotten in the tree.
This allows tree traversal with
struct tree_desc desc;
struct name_entry entry;
desc.buf = tree->buffer;
desc.size = tree->size;
while (tree_entry(&desc, &entry) {
... use "entry.{path, sha1, mode, pathlen}" ...
}
which is not only shorter than writing it out in full, it's hopefully less
error prone too.
[ It's actually a tad faster too - we don't need to recalculate the entry
pathlength in both extract and update, but need to do it only once.
Also, some callers can avoid doing a "strlen()" on the result, since
it's returned as part of the name_entry structure.
However, by now we're talking just 1% speedup on "git-rev-list --objects
--all", and we're definitely at the point where tree walking is no
longer the issue any more. ]
NOTE! Not everybody wants to use this new helper function, since some of
the tree walkers very much on purpose do the descriptor update separately
from the entry extraction. So the "extract + update" sequence still
remains as the core sequence, this is just a simplified interface.
We should probably add a silly two-line inline helper function for
initializing the descriptor from the "struct tree" too, just to cut down
on the noise from that common "desc" initializer.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This provides a linear decrement on the penalty related to delta depth
instead of being an 1/x function. With this another 5% reduction is
observed on packs for both the GIT repo and the Linux kernel repo, as
well as fixing a pack size regression in another sample repo I have.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Apparently <stdint.h> is not enough for uint32_t on OpenBSD; use
"unsigned int" -- hopefully that would stay 32-bit on every
platform we care about, at least until we update the pack-index
file format.
Our sha1 routines optimized for architectures use uint32_t and
expects '#include <stdint.h>' to be enough, so OpenBSD on arm or
ppc might have similar issues down the road, I dunno.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Avoid creating a delta index for objects with maximum depth since they
are not going to be used as delta base anyway. This also reduce peak
memory usage slightly as the current object's delta index is not useful
until the next object in the loop is considered for deltification. This
saves a bit more than 1% on CPU usage.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Given that the early eviction of objects with maximum delta depth
may exhibit bad packing on its own, why not considering a bias against
deep base objects in try_delta() to mitigate that bad behavior.
This patch adjust the MAX_size allowed for a delta based on the depth of
the base object as well as enabling the early eviction of max depth
objects from the object window. When used separately, those two things
produce slightly better and much worse results respectively. But their
combined effect is a surprising significant packing improvement.
With this really simple patch the GIT repo gets nearly 15% smaller, and
the Linux kernel repo about 5% smaller, with no significantly measurable
CPU usage difference.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
The offset of an object in the pack is recorded as a 4-byte integer
in the index file. When reading the offset from the mmap'ed index
in prepare_pack_revindex(), the address is dereferenced as a long*.
This works fine as long as the long type is four bytes wide. On
NetBSD/sparc64, however, a long is 8 bytes wide and so dereferencing
the offset produces garbage.
[jc: taking suggestion by Linus to use uint32_t]
Signed-off-by: Dennis Stosberg <dennis@stosberg.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>
One of my post-update scripts runs a git-fetch into a separate
repository and sends the results back to me (2>&1); I end up
getting this in the mail:
Generating pack...
Done counting 180 objects.
Result has 131 objects.
Deltifying 131 objects.
0% (0/131) done^M 1% (2/131) done^M...
This defaults not to do the progress report when not on a tty.
You could give --progress to force the progress report, but
let's not bother even documenting it nor mentioning it in the
usage string.
Signed-off-by: Junio C Hamano <junkio@cox.net>
We used to omit delta base candidates that is much bigger than
the target, but delta size does not grow when we delete more, so
that was not a very good heuristics.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This patch allows for computing the delta index for each base object
only once and reuse it when trying to find the best delta match.
This should set the mark and pave the way for possibly better delta
generator algorithms.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
The input line has 40 _chars_ of sha1 and no 20 _bytes_. It should also
account for the space before the pathname, and the terminating \n and \0.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Because we sort the delta window by name-hash and then size,
hitting an object that is too small to consider as a delta base
for the current object does not mean we do not have better
candidate in the window beyond it.
Noticed by Shawn Pearce, analyzed by Nico, Linus and me.
Signed-off-by: Junio C Hamano <junkio@cox.net>
It appears the fingerprinting itself is too expensive to be worth doing
for this purpose. A failed experiment.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Jens Axboe noticed that recent "git push" has become very slow
since we made --thin transfer the default.
Thin pack generation to push a handful revisions that touch
relatively small number of paths out of huge tree was stupid; it
registered _everything_ from the excluded revisions. As a
result, "Counting objects" phase was unnecessarily expensive.
This changes the logic to register the blobs and trees from
excluded revisions only for paths we are actually going to send
to the other end.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This replaces occurences of "blob", "commit", "tag", and "tree",
where they're really used as type specifiers, which we already
have defined global constants for.
Signed-off-by: Peter Eriksen <s022018@student.dtu.dk>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This is the "letter of the law" version of using fgets() properly in the
face of incredibly broken stdio implementations. We can work around the
Solaris breakage with SA_RESTART, but in case anybody else is ever that
stupid, here's the "safe" (read: "insanely anal") way to use fgets.
It probably goes without saying that I'm not terribly impressed by
Solaris libc.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This uses sigaction() to install the SIGALRM handler with SA_RESTART, so
that Solaris stdio doesn't break completely when a signal interrupts a
read.
Thanks to Jason Riedy for confirming the silly Solaris signal behaviour.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Introduce tree-walk.[ch] and move "struct tree_desc" and
associated functions from various places.
Rename DIFF_FILE_CANON_MODE(mode) macro to canon_mode(mode) and
move it to cache.h. This macro returns the canonicalized
st_mode value in the host byte order for files, symlinks and
directories -- to be compared with a tree_desc entry.
create_ce_mode(mode) in cache.h is similar but is intended to be
used for index entries (so it does not work for directories) and
returns the value in the network byte order.
Signed-off-by: Junio C Hamano <junkio@cox.net>
There was a misguided logic to overly prefer using objects that
we are not going to pack as the base object. This was
unnecessary. It does not matter to the unpacking side where the
base object is -- it matters more to make the resulting delta
smaller.
Signed-off-by: Junio C Hamano <junkio@cox.net>
When a reference buffer is used multiple times then its index can be
computed only once and reused multiple times. This patch adds an extra
pointer to a pointer argument (from_index) to diff_delta() for this.
If from_index is NULL then everything is like before.
If from_index is non NULL and *from_index is NULL then the index is
created and its location stored to *from_index. In this case the caller
has the responsibility to free the memory pointed to by *from_index.
If from_index and *from_index are non NULL then the index is reused as
is.
This currently saves about 10% of CPU time to repack the git archive.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Commit 8fcf1ad9c6 has a
combination of double cast and Andreas' switch to using
unsigned long ... just the latter is sufficient (and a lot less
ugly than using the double cast).
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
- Fix -Wundef -Wold-style-definition warnings
- Make pll_free() static
[jc: original patch by Timo had another unrelated bits:
- Use setenv() instead of putenv()
I'm postponing that part for now.]
Signed-off-by: Timo Hirvonen <tihirvon@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
When compiling on ia64 I get this warning (from gcc 3.4.3):
gcc -o pack-objects.o -c -g -O2 -Wall -DSHA1_HEADER='<openssl/sha.h>' pack-objects.c
pack-objects.c: In function `pack_revindex_ix':
pack-objects.c:94: warning: cast from pointer to integer of different size
A double cast (first to long, then to int) shuts gcc up, but is there
a better way?
[jc: Andreas Ericsson suggests to use ulong instead. ]
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
...so that "Makefile"s from different revs are sorted together,
separate from "t/Makefile"s, but close enough.
Signed-off-by: Junio C Hamano <junkio@cox.net>
When creating a new pack to be used in .git/objects/pack/
directory, we carefully count the depth of deltified objects to
be reused, so that the generated pack does not to exceed the
specified depth limit for runtime efficiency. However, when we
are generating a thin pack that does not contain base objects,
such a pack can only be used during network transfer that is
expanded on the other end upon reception, so being careful and
artificially cutting the delta chain does not buy us anything
except increased bandwidth requirement. This patch disables the
delta chain depth limit check when reusing an existing delta.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This uses the same hashing algorithm to the "preferred base
tree" objects and the incoming pathnames, to group the same
files from different revs together, while spreading files with
the same basename in different directories.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Since we sort objects by type, hash, preferredness and then
size, after we have a delta against preferred base, there is no
point trying a delta with non-preferred base. This seems to
save expensive calls to diff-delta and it also seems to save the
output space as well.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This updates the progress output to match "every one second or
every percent whichever comes early" used by unpack-objects, as
discussed on the list.
Signed-off-by: Junio C Hamano <junkio@cox.net>
If that pack is big, it takes significant time to write and might
benefit from some more eye candies as well. This is however disabled
when the pack is written to stdout since in that case the output is
usually piped into unpack_objects which already does its own progress
reporting.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This provides a stable and simpler progress reporting mechanism that
updates progress as often as possible but accurately not updating more
than once a second. The deltification phase is also made more
interesting to watch (since repacking a big repository and only seeing a
dot appear once every many seconds is rather boring and doesn't provide
much food for anticipation).
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This tries to rework the solution for the excess delta chain
problem. An earlier commit worked it around ``cheaply'', but
repeated repacking risks unbound growth of delta chains.
This version counts the length of delta chain we are reusing
from the existing pack, and makes sure a base object that has
sufficiently long delta chain does not get deltified.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This introduces --no-reuse-delta option to disable reusing of
existing delta, which is a large part of the optimization
introduced by this series. This may become necessary if
repeated repacking makes delta chain too long. With this, the
output of the command becomes identical to that of the older
implementation. But the performance suffers greatly.
It still allows reusing non-deltified representations; there is
no point uncompressing and recompressing the whole text.
It also adds a couple more statistics output, while squelching
it under -q flag, which the last round forgot to do.
$ time old-git-pack-objects --stdout >/dev/null <RL
Generating pack...
Done counting 184141 objects.
Packing 184141 objects....................
real 12m8.530s user 11m1.450s sys 0m57.920s
$ time git-pack-objects --stdout >/dev/null <RL
Generating pack...
Done counting 184141 objects.
Packing 184141 objects.....................
Total 184141, written 184141 (delta 138297), reused 178833 (delta 134081)
real 0m59.549s user 0m56.670s sys 0m2.400s
$ time git-pack-objects --stdout --no-reuse-delta >/dev/null <RL
Generating pack...
Done counting 184141 objects.
Packing 184141 objects.....................
Total 184141, written 184141 (delta 134833), reused 47904 (delta 0)
real 11m13.830s user 9m45.240s sys 0m44.330s
There is one remaining issue when --no-reuse-delta option is not
used. It can create delta chains that are deeper than specified.
A<--B<--C<--D E F G
Suppose we have a delta chain A to D (A is stored in full either
in a pack or as a loose object. B is depth1 delta relative to A,
C is depth2 delta relative to B...) with loose objects E, F, G.
And we are going to pack all of them.
B, C and D are left as delta against A, B and C respectively.
So A, E, F, and G are examined for deltification, and let's say
we decided to keep E expanded, and store the rest as deltas like
this:
E<--F<--G<--A
Oops. We ended up making D a bit too deep, didn't we? B, C and
D form a chain on top of A!
This is because we did not know what the final depth of A would
be, when we checked objects and decided to keep the existing
delta. Unfortunately, deferring the decision until just before
the deltification is not an option. To be able to make B, C,
and D candidates for deltification with the rest, we need to
know the type and final unexpanded size of them, but the major
part of the optimization comes from the fact that we do not read
the delta data to do so -- getting the final size is quite an
expensive operation.
To prevent this from happening, we should keep A from being
deltified. But how would we tell that, cheaply?
To do this most precisely, after check_object() runs, each
object that is used as the base object of some existing delta
needs to be marked with the maximum depth of the objects we
decided to keep deltified (in this case, D is depth 3 relative
to A, so if no other delta chain that is longer than 3 based on
A exists, mark A with 3). Then when attempting to deltify A, we
would take that number into account to see if the final delta
chain that leads to D becomes too deep.
However, this is a bit cumbersome to compute, so we would cheat
and reduce the maximum depth for A arbitrarily to depth/4 in
this implementation.
Signed-off-by: Junio C Hamano <junkio@cox.net>
When generating a new pack, notice if we have already needed
objects in existing packs. If an object is stored deltified,
and its base object is also what we are going to pack, then
reuse the existing deltified representation unconditionally,
bypassing all the expensive find_deltas() and try_deltas()
calls.
Also, notice if what we are going to write out exactly match
what is already in an existing pack (either deltified or just
compressed). In such a case, we can just copy it instead of
going through the usual uncompressing & recompressing cycle.
Without this patch, in linux-2.6 repository with about 1500
loose objects and a single mega pack:
$ git-rev-list --objects v2.6.16-rc3 >RL
$ wc -l RL
184141 RL
$ time git-pack-objects p <RL
Generating pack...
Done counting 184141 objects.
Packing 184141 objects....................
a1fc7b3e537fcb9b3c46b7505df859f0a11e79d2
real 12m4.323s
user 11m2.560s
sys 0m55.950s
With this patch, the same input:
$ time ../git.junio/git-pack-objects q <RL
Generating pack...
Done counting 184141 objects.
Packing 184141 objects.....................
a1fc7b3e537fcb9b3c46b7505df859f0a11e79d2
Total 184141, written 184141, reused 182441
real 1m2.608s
user 0m55.090s
sys 0m1.830s
Signed-off-by: Junio C Hamano <junkio@cox.net>
This change provides a 8% saving on the pack size with a 4% CPU time
increase for git-repack -a on the current git archive.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This goes together with "rev-list --object-edge" change, to feed
pack-objects list of edge commits in addition to the usual
object list. Upon seeing such list, pack-objects loosens the
usual "self contained delta" constraints, and can produce delta
against blobs and trees contained in the edge commits without
storing the delta base objects themselves.
The resulting packfile is not usable in .git/object/packs, but
is a good way to implement "delta-only" transfer.
Signed-off-by: Junio C Hamano <junkio@cox.net>
René Scharfe