зеркало из https://github.com/microsoft/git.git
[PATCH] mkdelta enhancements (take 2)
Although it was described as such, git-mkdelta didn't really attempt to find the best delta against any previous object in the list, but was only able to create a delta against the preceeding object. This patch reworks the code to fix that limitation and hopefully makes it a bit clearer than before, including fixing the delta loop detection which was broken. This means that git-mkdelta sha1 sha2 sha3 sha4 sha5 sha6 will now create a sha2 delta against sha1, a sha3 delta against either sha2 or sha1 and keep the best one, a sha4 delta against either sha3, sha2 or sha1, etc. The --max-behind argument limits that search for the best delta to the specified number of previous objects in the list. If no limit is specified it is unlimited (note: it might run out of memory with long object lists). Also added a -q (quiet) switch so it is possible to have 3 levels of output: -q for nothing, -v for verbose, and if none of -q nor -v is specified then only actual changes on the object database are shown. Finally the git-deltafy-script has been updated accordingly, and some bugs fixed (thanks to Stephen C. Tweedie for spotting them). This version has been toroughly tested and I think it is ready for public consumption. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nicolas Pitre
Linus Torvalds
Родитель
a3e870f2e2
Коммит
53d4b46085
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@ -1,40 +1,67 @@
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#!/bin/bash
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# Script to deltafy an entire GIT repository based on the commit list.
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# Example script to deltafy an entire GIT repository based on the commit list.
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# The most recent version of a file is the reference and previous versions
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# are made delta against the best earlier version available. And so on for
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# successive versions going back in time. This way the delta overhead is
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# pushed towards older version of any given file.
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#
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# NOTE: the "best earlier version" is not implemented in mkdelta yet
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# and therefore only the next eariler version is used at this time.
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#
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# TODO: deltafy tree objects as well.
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# successive versions going back in time. This way the increasing delta
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# overhead is pushed towards older versions of any given file.
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#
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# The -d argument allows to provide a limit on the delta chain depth.
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# If 0 is passed then everything is undeltafied.
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# If 0 is passed then everything is undeltafied. Limiting the delta
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# depth is meaningful for subsequent access performance to old revisions.
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# A value of 16 might be a good compromize between performance and good
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# space saving. Current default is unbounded.
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#
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# The --max-behind=30 argument is passed to git-mkdelta so to keep
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# combinations and memory usage bounded a bit. If you have lots of memory
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# and CPU power you may remove it (or set to 0) to let git-mkdelta find the
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# best delta match regardless of the number of revisions for a given file.
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# You can also make the value smaller to make it faster and less
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# memory hungry. A value of 5 ought to still give pretty good results.
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# When set to 0 or ommitted then look behind is unbounded. Note that
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# git-mkdelta might die with a segmentation fault in that case if it
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# runs out of memory. Note that the GIT repository will still be consistent
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# even if git-mkdelta dies unexpectedly.
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set -e
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depth=
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[ "$1" == "-d" ] && depth="--max-depth=$2" && shift 2
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function process_list() {
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if [ "$list" ]; then
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echo "Processing $curr_file"
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echo "$head $list" | xargs git-mkdelta $depth --max-behind=30 -v
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fi
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}
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curr_file=""
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git-rev-list HEAD |
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git-diff-tree -r --stdin |
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awk '/^:/ { if ($5 == "M" || $5 == "N") print $4, $6 }' |
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git-diff-tree -r -t --stdin |
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awk '/^:/ { if ($5 == "M" || $5 == "N") print $4, $6;
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if ($5 == "M") print $3, $6 }' |
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LC_ALL=C sort -s -k 2 | uniq |
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while read sha1 file; do
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if [ "$file" == "$curr_file" ]; then
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list="$list $sha1"
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else
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if [ "$list" ]; then
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echo "Processing $curr_file"
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echo "$head $list" | xargs git-mkdelta $depth -v
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fi
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process_list
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curr_file="$file"
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list=""
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head="$sha1"
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fi
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done
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process_list
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curr_file="root directory"
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head=""
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list="$(
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git-rev-list HEAD |
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while read commit; do
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git-cat-file commit $commit |
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sed -n 's/tree //p;Q'
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done
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)"
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process_list
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360
mkdelta.c
360
mkdelta.c
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@ -98,21 +98,16 @@ static void *create_delta_object(char *buf, unsigned long len,
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return create_object(buf, len, hdr, hdrlen, size);
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}
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static unsigned long get_object_size(unsigned char *sha1)
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{
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struct stat st;
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if (stat(sha1_file_name(sha1), &st))
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die("%s: %s", sha1_to_hex(sha1), strerror(errno));
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return st.st_size;
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}
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static void *get_buffer(unsigned char *sha1, char *type, unsigned long *size)
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static void *get_buffer(unsigned char *sha1, char *type,
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unsigned long *size, unsigned long *compsize)
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{
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unsigned long mapsize;
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void *map = map_sha1_file(sha1, &mapsize);
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if (map) {
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void *buffer = unpack_sha1_file(map, mapsize, type, size);
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munmap(map, mapsize);
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if (compsize)
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*compsize = mapsize;
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if (buffer)
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return buffer;
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}
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@ -120,198 +115,249 @@ static void *get_buffer(unsigned char *sha1, char *type, unsigned long *size)
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return NULL;
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}
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static void *expand_delta(void *delta, unsigned long delta_size, char *type,
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unsigned long *size, unsigned int *depth, char *head)
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static void *expand_delta(void *delta, unsigned long *size, char *type,
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unsigned int *depth, unsigned char **links)
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{
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void *buf = NULL;
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*depth++;
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if (delta_size < 20) {
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unsigned int level = (*depth)++;
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if (*size < 20) {
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error("delta object is bad");
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free(delta);
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} else {
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unsigned long ref_size;
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void *ref = get_buffer(delta, type, &ref_size);
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void *ref = get_buffer(delta, type, &ref_size, NULL);
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if (ref && !strcmp(type, "delta"))
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ref = expand_delta(ref, ref_size, type, &ref_size,
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depth, head);
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else
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memcpy(head, delta, 20);
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if (ref)
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buf = patch_delta(ref, ref_size, delta+20,
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delta_size-20, size);
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free(ref);
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ref = expand_delta(ref, &ref_size, type, depth, links);
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else if (ref)
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{
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*links = xmalloc(*depth * 20);
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}
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if (ref) {
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buf = patch_delta(ref, ref_size, delta+20, *size-20, size);
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free(ref);
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if (buf)
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memcpy(*links + level*20, delta, 20);
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else
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free(*links);
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}
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free(delta);
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}
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return buf;
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}
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static char *mkdelta_usage =
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"mkdelta [ --max-depth=N ] <reference_sha1> <target_sha1> [ <next_sha1> ... ]";
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"mkdelta [--max-depth=N] [--max-behind=N] <reference_sha1> <target_sha1> [<next_sha1> ...]";
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struct delta {
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unsigned char sha1[20]; /* object sha1 */
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unsigned long size; /* object size */
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void *buf; /* object content */
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unsigned char *links; /* delta reference links */
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unsigned int depth; /* delta depth */
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};
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int main(int argc, char **argv)
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{
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unsigned char sha1_ref[20], sha1_trg[20], head_ref[20], head_trg[20];
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char type_ref[20], type_trg[20];
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void *buf_ref, *buf_trg, *buf_delta;
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unsigned long size_ref, size_trg, size_orig, size_delta;
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unsigned int depth_ref, depth_trg, depth_max = -1;
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int i, verbose = 0;
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struct delta *ref, trg;
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char ref_type[20], trg_type[20], *skip_reason;
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void *best_buf;
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unsigned long best_size, orig_size, orig_compsize;
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unsigned int r, orig_ref, best_ref, nb_refs, next_ref, max_refs = 0;
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unsigned int i, duplicate, skip_lvl, verbose = 0, quiet = 0;
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unsigned int max_depth = -1;
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for (i = 1; i < argc; i++) {
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if (!strcmp(argv[i], "-v")) {
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verbose = 1;
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quiet = 0;
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} else if (!strcmp(argv[i], "-q")) {
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quiet = 1;
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verbose = 0;
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} else if (!strcmp(argv[i], "-d") && i+1 < argc) {
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depth_max = atoi(argv[++i]);
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max_depth = atoi(argv[++i]);
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} else if (!strncmp(argv[i], "--max-depth=", 12)) {
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depth_max = atoi(argv[i]+12);
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max_depth = atoi(argv[i]+12);
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} else if (!strcmp(argv[i], "-b") && i+1 < argc) {
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max_refs = atoi(argv[++i]);
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} else if (!strncmp(argv[i], "--max-behind=", 13)) {
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max_refs = atoi(argv[i]+13);
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} else
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break;
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}
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if (i + (depth_max != 0) >= argc)
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if (i + (max_depth != 0) >= argc)
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usage(mkdelta_usage);
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if (get_sha1(argv[i], sha1_ref))
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die("bad sha1 %s", argv[i]);
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depth_ref = 0;
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buf_ref = get_buffer(sha1_ref, type_ref, &size_ref);
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if (buf_ref && !strcmp(type_ref, "delta"))
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buf_ref = expand_delta(buf_ref, size_ref, type_ref,
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&size_ref, &depth_ref, head_ref);
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else
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memcpy(head_ref, sha1_ref, 20);
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if (!buf_ref)
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die("unable to obtain initial object %s", argv[i]);
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if (!max_refs || max_refs > argc - i)
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max_refs = argc - i;
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ref = xmalloc(max_refs * sizeof(*ref));
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for (r = 0; r < max_refs; r++)
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ref[r].buf = ref[r].links = NULL;
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next_ref = nb_refs = 0;
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if (depth_ref > depth_max) {
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if (restore_original_object(buf_ref, size_ref, type_ref, sha1_ref))
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die("unable to restore %s", argv[i]);
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if (verbose)
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printf("undelta %s (depth was %d)\n", argv[i], depth_ref);
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depth_ref = 0;
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}
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/*
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* TODO: deltafication should be tried against any early object
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* in the object list and not only the previous object.
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*/
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while (++i < argc) {
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if (get_sha1(argv[i], sha1_trg))
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do {
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if (get_sha1(argv[i], trg.sha1))
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die("bad sha1 %s", argv[i]);
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depth_trg = 0;
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buf_trg = get_buffer(sha1_trg, type_trg, &size_trg);
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if (buf_trg && !size_trg) {
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trg.buf = get_buffer(trg.sha1, trg_type, &trg.size, &orig_compsize);
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if (trg.buf && !trg.size) {
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if (verbose)
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printf("skip %s (object is empty)\n", argv[i]);
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continue;
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}
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size_orig = size_trg;
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if (buf_trg && !strcmp(type_trg, "delta")) {
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if (!memcmp(buf_trg, sha1_ref, 20)) {
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/* delta already in place */
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depth_ref++;
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memcpy(sha1_ref, sha1_trg, 20);
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buf_ref = patch_delta(buf_ref, size_ref,
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buf_trg+20, size_trg-20,
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&size_ref);
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if (!buf_ref)
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die("unable to apply delta %s", argv[i]);
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if (depth_ref > depth_max) {
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if (restore_original_object(buf_ref, size_ref,
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type_ref, sha1_ref))
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die("unable to restore %s", argv[i]);
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if (verbose)
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printf("undelta %s (depth was %d)\n", argv[i], depth_ref);
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depth_ref = 0;
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continue;
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}
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if (verbose)
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printf("skip %s (delta already in place)\n", argv[i]);
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continue;
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orig_size = trg.size;
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orig_ref = -1;
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trg.depth = 0;
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trg.links = NULL;
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if (trg.buf && !strcmp(trg_type, "delta")) {
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for (r = 0; r < nb_refs; r++)
|
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if (!memcmp(trg.buf, ref[r].sha1, 20))
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break;
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if (r < nb_refs) {
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/* no need to reload the reference object */
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||||
trg.depth = ref[r].depth + 1;
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trg.links = xmalloc(trg.depth*20);
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memcpy(trg.links, trg.buf, 20);
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memcpy(trg.links+20, ref[r].links, ref[r].depth*20);
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trg.buf = patch_delta(ref[r].buf, ref[r].size,
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||||
trg.buf+20, trg.size-20,
|
||||
&trg.size);
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||||
strcpy(trg_type, ref_type);
|
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orig_ref = r;
|
||||
} else {
|
||||
trg.buf = expand_delta(trg.buf, &trg.size, trg_type,
|
||||
&trg.depth, &trg.links);
|
||||
}
|
||||
buf_trg = expand_delta(buf_trg, size_trg, type_trg,
|
||||
&size_trg, &depth_trg, head_trg);
|
||||
} else
|
||||
memcpy(head_trg, sha1_trg, 20);
|
||||
if (!buf_trg)
|
||||
}
|
||||
if (!trg.buf)
|
||||
die("unable to read target object %s", argv[i]);
|
||||
|
||||
if (depth_trg > depth_max) {
|
||||
if (restore_original_object(buf_trg, size_trg, type_trg, sha1_trg))
|
||||
die("unable to restore %s", argv[i]);
|
||||
if (verbose)
|
||||
printf("undelta %s (depth was %d)\n", argv[i], depth_trg);
|
||||
depth_trg = 0;
|
||||
size_orig = size_trg;
|
||||
}
|
||||
|
||||
if (depth_max == 0)
|
||||
goto skip;
|
||||
|
||||
if (strcmp(type_ref, type_trg))
|
||||
if (!nb_refs) {
|
||||
strcpy(ref_type, trg_type);
|
||||
} else if (max_depth && strcmp(ref_type, trg_type)) {
|
||||
die("type mismatch for object %s", argv[i]);
|
||||
|
||||
if (!size_ref) {
|
||||
if (verbose)
|
||||
printf("skip %s (initial object is empty)\n", argv[i]);
|
||||
goto skip;
|
||||
}
|
||||
|
||||
if (depth_ref + 1 > depth_max) {
|
||||
if (verbose)
|
||||
printf("skip %s (exceeding max link depth)\n", argv[i]);
|
||||
goto skip;
|
||||
}
|
||||
|
||||
if (!memcmp(head_ref, sha1_trg, 20)) {
|
||||
if (verbose)
|
||||
printf("skip %s (would create a loop)\n", argv[i]);
|
||||
goto skip;
|
||||
}
|
||||
duplicate = 0;
|
||||
best_buf = NULL;
|
||||
best_size = -1;
|
||||
best_ref = -1;
|
||||
skip_lvl = 0;
|
||||
skip_reason = NULL;
|
||||
for (r = 0; max_depth && r < nb_refs; r++) {
|
||||
void *delta_buf, *comp_buf;
|
||||
unsigned long delta_size, comp_size;
|
||||
unsigned int l;
|
||||
|
||||
buf_delta = diff_delta(buf_ref, size_ref, buf_trg, size_trg, &size_delta);
|
||||
if (!buf_delta)
|
||||
die("out of memory");
|
||||
|
||||
/* no need to even try to compress if original
|
||||
uncompressed is already smaller */
|
||||
if (size_delta+20 < size_orig) {
|
||||
void *buf_obj;
|
||||
unsigned long size_obj;
|
||||
buf_obj = create_delta_object(buf_delta, size_delta,
|
||||
sha1_ref, &size_obj);
|
||||
free(buf_delta);
|
||||
size_orig = get_object_size(sha1_trg);
|
||||
if (size_obj >= size_orig) {
|
||||
free(buf_obj);
|
||||
if (verbose)
|
||||
printf("skip %s (original is smaller)\n", argv[i]);
|
||||
goto skip;
|
||||
duplicate = !memcmp(trg.sha1, ref[r].sha1, 20);
|
||||
if (duplicate) {
|
||||
skip_reason = "already seen";
|
||||
break;
|
||||
}
|
||||
if (ref[r].depth >= max_depth) {
|
||||
if (skip_lvl < 1) {
|
||||
skip_reason = "exceeding max link depth";
|
||||
skip_lvl = 1;
|
||||
}
|
||||
continue;
|
||||
}
|
||||
for (l = 0; l < ref[r].depth; l++)
|
||||
if (!memcmp(trg.sha1, ref[r].links + l*20, 20))
|
||||
break;
|
||||
if (l != ref[r].depth) {
|
||||
if (skip_lvl < 2) {
|
||||
skip_reason = "would create a loop";
|
||||
skip_lvl = 2;
|
||||
}
|
||||
continue;
|
||||
}
|
||||
if (trg.depth < max_depth && r == orig_ref) {
|
||||
if (skip_lvl < 3) {
|
||||
skip_reason = "delta already in place";
|
||||
skip_lvl = 3;
|
||||
}
|
||||
continue;
|
||||
}
|
||||
delta_buf = diff_delta(ref[r].buf, ref[r].size,
|
||||
trg.buf, trg.size, &delta_size);
|
||||
if (!delta_buf)
|
||||
die("out of memory");
|
||||
if (trg.depth < max_depth &&
|
||||
delta_size+20 >= orig_size) {
|
||||
/* no need to even try to compress if original
|
||||
object is smaller than this delta */
|
||||
free(delta_buf);
|
||||
if (skip_lvl < 4) {
|
||||
skip_reason = "no size reduction";
|
||||
skip_lvl = 4;
|
||||
}
|
||||
continue;
|
||||
}
|
||||
comp_buf = create_delta_object(delta_buf, delta_size,
|
||||
ref[r].sha1, &comp_size);
|
||||
if (!comp_buf)
|
||||
die("out of memory");
|
||||
free(delta_buf);
|
||||
if (trg.depth < max_depth &&
|
||||
comp_size >= orig_compsize) {
|
||||
free(comp_buf);
|
||||
if (skip_lvl < 5) {
|
||||
skip_reason = "no size reduction";
|
||||
skip_lvl = 5;
|
||||
}
|
||||
continue;
|
||||
}
|
||||
if ((comp_size < best_size) ||
|
||||
(comp_size == best_size &&
|
||||
ref[r].depth < ref[best_ref].depth)) {
|
||||
free(best_buf);
|
||||
best_buf = comp_buf;
|
||||
best_size = comp_size;
|
||||
best_ref = r;
|
||||
}
|
||||
if (replace_object(buf_obj, size_obj, sha1_trg))
|
||||
die("unable to write delta for %s", argv[i]);
|
||||
free(buf_obj);
|
||||
depth_ref++;
|
||||
if (verbose)
|
||||
printf("delta %s (size=%ld.%02ld%%, depth=%d)\n",
|
||||
argv[i], size_obj*100 / size_orig,
|
||||
(size_obj*10000 / size_orig)%100,
|
||||
depth_ref);
|
||||
} else {
|
||||
free(buf_delta);
|
||||
if (verbose)
|
||||
printf("skip %s (original is smaller)\n", argv[i]);
|
||||
skip:
|
||||
depth_ref = depth_trg;
|
||||
memcpy(head_ref, head_trg, 20);
|
||||
}
|
||||
|
||||
free(buf_ref);
|
||||
buf_ref = buf_trg;
|
||||
size_ref = size_trg;
|
||||
memcpy(sha1_ref, sha1_trg, 20);
|
||||
}
|
||||
if (best_buf) {
|
||||
if (replace_object(best_buf, best_size, trg.sha1))
|
||||
die("unable to write delta for %s", argv[i]);
|
||||
free(best_buf);
|
||||
free(trg.links);
|
||||
trg.depth = ref[best_ref].depth + 1;
|
||||
trg.links = xmalloc(trg.depth*20);
|
||||
memcpy(trg.links, ref[best_ref].sha1, 20);
|
||||
memcpy(trg.links+20, ref[best_ref].links, ref[best_ref].depth*20);
|
||||
if (!quiet)
|
||||
printf("delta %s (size=%ld.%02ld%% depth=%d dist=%d)\n",
|
||||
argv[i], best_size*100 / orig_compsize,
|
||||
(best_size*10000 / orig_compsize)%100,
|
||||
trg.depth,
|
||||
(next_ref - best_ref + max_refs)
|
||||
% (max_refs + 1) + 1);
|
||||
} else if (trg.depth > max_depth) {
|
||||
if (restore_original_object(trg.buf, trg.size, trg_type, trg.sha1))
|
||||
die("unable to restore %s", argv[i]);
|
||||
if (!quiet)
|
||||
printf("undelta %s (depth was %d)\n",
|
||||
argv[i], trg.depth);
|
||||
trg.depth = 0;
|
||||
free(trg.links);
|
||||
trg.links = NULL;
|
||||
} else if (skip_reason && verbose) {
|
||||
printf("skip %s (%s)\n", argv[i], skip_reason);
|
||||
}
|
||||
|
||||
if (!duplicate) {
|
||||
free(ref[next_ref].buf);
|
||||
free(ref[next_ref].links);
|
||||
ref[next_ref] = trg;
|
||||
if (++next_ref > nb_refs)
|
||||
nb_refs = next_ref;
|
||||
if (next_ref == max_refs)
|
||||
next_ref = 0;
|
||||
} else {
|
||||
free(trg.buf);
|
||||
free(trg.links);
|
||||
}
|
||||
} while (++i < argc);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
|
|
|||
Загрузка…
Ссылка в новой задаче