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It cannot be assumed that the given buffer will never be moved when
shrinking the allocated memory size with realloc(). So let's ignore
that optimization for now.
This patch makes Electric Fence happy on Linux.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Acked-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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It is useless to preserve multiple hash entries for consecutive blocks
with the same hash. Keeping only the first one will allow for matching
the longest string of identical bytes while subsequent blocks will only
allow for shorter matches. The backward matching code will match the
end of it as necessary.
This improves both performances (no repeated string compare with long
successions of identical bytes, or even small group of bytes), as well
as compression (less likely to need random hash bucket entry culling),
especially with sparse files.
With well behaved data sets this patch doesn't change much.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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This is my assembly freak side looking at generated code again. And
since create_delta() is certainly pretty high on the radar every bits
count. In this case shorter code is generated if hash_mask is not
copied to a local variable.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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This brings another small repacking speedup for sensibly the same pack
size. On the Linux kernel repo, git-repack -a -f is 3.7% faster for a
0.4% larger pack.
Credits to Geert Bosch who brought the Rabin's polynomial idea to my
attention.
This also eliminate the issue of adler32() reading past the data buffer,
as noticed by Johannes Schindelin.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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This patch splits the diff-delta interface into index creation and delta
generation. A wrapper is provided to preserve the diff-delta() call.
This will allow for an optimization in pack-objects.c where the source
object could be fixed and a full window of objects tentatively tried
against
that same source object without recomputing the source index each time.
This patch only restructure things, plus a couple cleanups for good
measure. There is no performance change yet.
Signed-off-by: Nicolas Pitre <nico@cam.org>
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This patch makes for 3.4% smaller pack with the git repository, and
a bit more than 3% smaller pack with the kernel repository.
And so with _no_ measurable CPU difference.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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The diff-delta code can exhibit O(m*n) behavior with some patological
data set where most hash entries end up in the same hash bucket.
To prevent this, a limit is imposed to the number of entries that can
exist in the same hash bucket.
Because of the above the code is a tiny bit more expensive on average,
even if some small optimizations were added as well to atenuate the
overhead. But the problematic samples used to diagnoze the issue are now
orders of magnitude less expensive to process with only a slight loss in
compression.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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This is much smaller and hopefully clearer code now.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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Testing for realloc and size limit can be done with only one test per
loop. Make it so and fix a theoretical off-by-one comparison error in
the process.
The output buffer memory allocation is also bounded by max_size when
specified.
Finally make some variable unsigned to allow the handling of files up to
4GB in size instead of 2GB.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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Since we already depend on zlib, we don't need to define our
own adler32(). Spotted by oprofile.
Signed-off-by: Peter Eriksen <s022018@student.dtu.dk>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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This patch removes unused remnants of the original xdiff source.
No functional change. Possible tiny speed improvement.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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This reverts 962537a3eb03a118cf27d9d0da365a3216ed1caa commit to
play safe.
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Delta computation with an empty blob used to punt and returned NULL.
This commit allows creation with empty blob; all combination of
empty->empty, empty->something, and something->empty are allowed.
Signed-off-by: Junio C Hamano <junkio@cox.net>
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This is a wrap-up patch including all the cleanups I've done to the
delta code and its usage. The most important change is the
factorization of the delta header handling code.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Since the delta data format is not tied to any actual git object
anymore, now is the time to add a small improvement to the delta data
header as it is been done for packed object header. This patch allows
for reducing the delta header of about 2 bytes and makes for simpler
code.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Anything that generates a delta to see if two objects are close usually
isn't interested in the delta ends up being bigger than some specified
size, and this allows us to stop delta generation early when that
happens.
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This patch adds the basic library functions to create and replay delta
information. Also included is a test-delta utility to validate the
code.
diff-delta was based on LibXDiff written by Davide Libenzi
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Nicolas Pitre
Peter Eriksen
Junio C Hamano
Linus Torvalds