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* diff-delta.c: Rationalize culling of hash bucketsDavid Kastrup2007-09-09
| | | | | | | | | | | | The previous hash bucket culling resulted in a somewhat unpredictable number of hash bucket entries in the order of magnitude of HASH_LIMIT. Replace this with a Bresenham-like algorithm leaving us with exactly HASH_LIMIT entries by uniform culling. Signed-off-by: David Kastrup <dak@gnu.org> Acked-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* diff-delta.c: pack the index structureDavid Kastrup2007-09-09
| | | | | | | | | | | | | | | | | | | | | | In normal use cases, the performance wins are not overly impressive: we get something like 5-10% due to the slightly better locality of memory accesses using the packed structure. However, since the data structure for index entries saves 33% of memory on 32-bit platforms and 40% on 64-bit platforms, the behavior when memory gets limited should be nicer. This is a rather well-contained change. One obvious improvement would be sorting the elements in one bucket according to their hash, then using binary probing to find the elements with the right hash value. As it stands, the output should be strictly the same as previously unless one uses the option for limiting the amount of used memory, in which case the created packs might be better. Signed-off-by: David Kastrup <dak@gnu.org> Acked-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* diff-delta.c: Fix broken skip calculation.David Kastrup2007-08-23
| | | | | | | | | | A particularly bad case was HASH_LIMIT <= hash_count[i] < 2*HASH_LIMIT: in that case, only a single hash survived. For larger cases, 2*HASH_LIMIT was the actual limiting value after pruning. Signed-off-by: David Kastrup <dak@gnu.org> Acked-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* Support fetching the memory usage of a delta indexBrian Downing2007-07-12
| | | | | | | | | | | | | | Delta indices, at least on 64-bit platforms, tend to be larger than the actual uncompressed data. As such, keeping track of this storage is important if you want to successfully limit the memory size of your pack window. Squirrel away the total allocation size inside the delta_index struct, and add an accessor "sizeof_delta_index" to access it. Signed-off-by: Brian Downing <bdowning@lavos.net> Acked-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* diff-delta: use realloc instead of xreallocMartin Koegler2007-05-31
| | | | | | | | | | | Commit 83572c1a914d3f7a8dd66d954c11bbc665b7b923 changed many realloc to xrealloc. This change was made in diff-delta.c too, although the code can handle an out of memory failure. This patch reverts this change in diff-delta.c. Signed-off-by: Martin Koegler <mkoegler@auto.tuwien.ac.at> Signed-off-by: Junio C Hamano <junkio@cox.net>
* update diff-delta.c copyrightNicolas Pitre2007-05-26
| | | | | | | | | | There is actually nothing left from the original LibXDiff code I used over 2 years ago, and even the GIT implementation has diverged quite a bit from LibXDiff's at this point. Let's update the copyright notice to better reflect that fact. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
* improve delta long block matching with big filesNicolas Pitre2007-05-26
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Martin Koegler noted that create_delta() performs a new hash lookup after every block copy encoding which are currently limited to 64KB. In case of larger identical blocks, the next hash lookup would normally point to the next 64KB block in the reference buffer and multiple block copy operations will be consecutively encoded. It is however possible that the reference buffer be sparsely indexed if hash buckets have been trimmed down in create_delta_index() when hashing of the reference buffer isn't well balanced. In that case the hash lookup following a block copy might fail to match anything and the fact that the reference buffer still matches beyond the previous 64KB block will be missed. Let's rework the code so that buffer comparison isn't bounded to 64KB anymore. The match size should be as large as possible up front and only then should multiple block copy be encoded to cover it all. Also, fewer hash lookups will be performed in the end. According to Martin, this patch should reduce his 92MB pack down to 75MB with the dataset he has. Tests performed on the Linux kernel repo show a slightly smaller pack and a slightly faster repack. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
* simplify inclusion of system header files.Junio C Hamano2006-12-20
| | | | | | | | | | | | | | | | | | | | 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>
* Revert "move pack creation to version 3"Junio C Hamano2006-10-14
| | | | | | | | | | | | | | This reverts commit 16854571aae6302f457c5fbee41ac64669b09595. Git as recent as v1.1.6 do not understand version 3 delta. v1.2.0 is Ok and I personally would say it is old enough, but the improvement between version 2 and version 3 delta is not bit enough to justify breaking older clients. We should resurrect this later, but when we do so we shold make it conditional. Signed-off-by: Junio C Hamano <junkio@cox.net>
* move pack creation to version 3Nicolas Pitre2006-09-22
| | | | | | | | It's been quite a while now that GIT is able to read version 3 packs. Let's create them at last. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
* Use xrealloc instead of reallocJonas Fonseca2006-08-26
| | | | | | | | | Change places that use realloc, without a proper error path, to instead use xrealloc. Drop an erroneous error path in the daemon code that used errno in the die message in favour of the simpler xrealloc. Signed-off-by: Jonas Fonseca <fonseca@diku.dk> Signed-off-by: Junio C Hamano <junkio@cox.net>
* Fix a comparison bug in diff-delta.cPierre Habouzit2006-08-23
| | | | | | | | | (1 << i) < hspace is compared in the `int` space rather that in the unsigned one. the result will be wrong if hspace is between 0x40000000 and 0x80000000. Signed-off-by: Pierre Habouzit <madcoder@debian.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
* Fix more typos, primarily in the codePavel Roskin2006-07-10
| | | | | | | | | 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>
* Remove all void-pointer arithmetic.Florian Forster2006-06-20
| | | | | | | | 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>
* Initialize FAMs using `FLEX_ARRAY'.Florian Forster2006-06-18
| | | | | | | | When initializing a `flexible array member' the macro `FLEX_ARRAY' should be used. This was forgotten in `diff-delta.c'. Signed-off-by: Florian Forster <octo@verplant.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
* fix diff-delta bad memory accessNicolas Pitre2006-05-10
| | | | | | | | | | | | 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>
* improve diff-delta with sparse and/or repetitive dataNicolas Pitre2006-05-02
| | | | | | | | | | | | | | | | | | 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>
* tiny optimization to diff-deltaNicolas Pitre2006-05-02
| | | | | | | | | | 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>
* replace adler32 with Rabin's polynomial in diff-deltaNicolas Pitre2006-04-28
| | | | | | | | | | | | | | | 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>
* split the diff-delta interfaceNicolas Pitre2006-04-24
| | | | | | | | | | | | | | | 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>
* 3% tighter packs for freeNicolas Pitre2006-03-17
| | | | | | | | | | 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>
* diff-delta: bound hash list length to avoid O(m*n) behaviorNicolas Pitre2006-03-09
| | | | | | | | | | | | | | | | | 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>
* diff-delta: big code simplificationNicolas Pitre2006-02-22
| | | | | | | 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>
* diff-delta: fold two special tests into one plus cleanupsNicolas Pitre2006-02-22
| | | | | | | | | | | | | | | 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>
* Use adler32() from zlib instead of defining our own.Peter Eriksen2006-02-05
| | | | | | | | 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>
* small cleanup for diff-delta.cNicolas Pitre2005-12-15
| | | | | | | | 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>
* Revert "diff-delta.c: allow delta with empty blob."Junio C Hamano2005-12-12
| | | | | This reverts 962537a3eb03a118cf27d9d0da365a3216ed1caa commit to play safe.
* diff-delta.c: allow delta with empty blob.Junio C Hamano2005-12-12
| | | | | | | | 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>
* [PATCH] assorted delta code cleanupNicolas Pitre2005-06-29
| | | | | | | | | 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>
* [PATCH] denser delta header encodingNicolas Pitre2005-06-28
| | | | | | | | | | | 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>
* Add a "max_size" parameter to diff_delta()Linus Torvalds2005-06-25
| | | | | | | 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.
* [PATCH] Deltification library work by Nicolas Pitre.Nicolas Pitre2005-05-19
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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