--- /dev/null
+NOTE: The configuration options in `bitmapPseudoMerge.*` are considered
+EXPERIMENTAL and may be subject to change or be removed entirely in the
+future. For more information about the pseudo-merge bitmap feature, see
+the "Pseudo-merge bitmaps" section of linkgit:gitpacking[7].
+
+bitmapPseudoMerge.<name>.pattern::
+ Regular expression used to match reference names. Commits
+ pointed to by references matching this pattern (and meeting
+ the below criteria, like `bitmapPseudoMerge.<name>.sampleRate`
+ and `bitmapPseudoMerge.<name>.threshold`) will be considered
+ for inclusion in a pseudo-merge bitmap.
++
+Commits are grouped into pseudo-merge groups based on whether or not
+any reference(s) that point at a given commit match the pattern, which
+is an extended regular expression.
++
+Within a pseudo-merge group, commits may be further grouped into
+sub-groups based on the capture groups in the pattern. These
+sub-groupings are formed from the regular expressions by concatenating
+any capture groups from the regular expression, with a '-' dash in
+between.
++
+For example, if the pattern is `refs/tags/`, then all tags (provided
+they meet the below criteria) will be considered candidates for the
+same pseudo-merge group. However, if the pattern is instead
+`refs/remotes/([0-9])+/tags/`, then tags from different remotes will
+be grouped into separate pseudo-merge groups, based on the remote
+number.
+
+bitmapPseudoMerge.<name>.decay::
+ Determines the rate at which consecutive pseudo-merge bitmap
+ groups decrease in size. Must be non-negative. This parameter
+ can be thought of as `k` in the function `f(n) = C * n^-k`,
+ where `f(n)` is the size of the `n`th group.
++
+Setting the decay rate equal to `0` will cause all groups to be the
+same size. Setting the decay rate equal to `1` will cause the `n`th
+group to be `1/n` the size of the initial group. Higher values of the
+decay rate cause consecutive groups to shrink at an increasing rate.
+The default is `1`.
++
+If all groups are the same size, it is possible that groups containing
+newer commits will be able to be used less often than earlier groups,
+since it is more likely that the references pointing at newer commits
+will be updated more often than a reference pointing at an old commit.
+
+bitmapPseudoMerge.<name>.sampleRate::
+ Determines the proportion of non-bitmapped commits (among
+ reference tips) which are selected for inclusion in an
+ unstable pseudo-merge bitmap. Must be between `0` and `1`
+ (inclusive). The default is `1`.
+
+bitmapPseudoMerge.<name>.threshold::
+ Determines the minimum age of non-bitmapped commits (among
+ reference tips, as above) which are candidates for inclusion
+ in an unstable pseudo-merge bitmap. The default is
+ `1.week.ago`.
+
+bitmapPseudoMerge.<name>.maxMerges::
+ Determines the maximum number of pseudo-merge commits among
+ which commits may be distributed.
++
+For pseudo-merge groups whose pattern does not contain any capture
+groups, this setting is applied for all commits matching the regular
+expression. For patterns that have one or more capture groups, this
+setting is applied for each distinct capture group.
++
+For example, if your capture group is `refs/tags/`, then this setting
+will distribute all tags into a maximum of `maxMerges` pseudo-merge
+commits. However, if your capture group is, say,
+`refs/remotes/([0-9]+)/tags/`, then this setting will be applied to
+each remote's set of tags individually.
++
+Must be non-negative. The default value is 64.
+
+bitmapPseudoMerge.<name>.stableThreshold::
+ Determines the minimum age of commits (among reference tips,
+ as above, however stable commits are still considered
+ candidates even when they have been covered by a bitmap) which
+ are candidates for a stable a pseudo-merge bitmap. The default
+ is `1.month.ago`.
++
+Setting this threshold to a smaller value (e.g., 1.week.ago) will cause
+more stable groups to be generated (which impose a one-time generation
+cost) but those groups will likely become stale over time. Using a
+larger value incurs the opposite penalty (fewer stable groups which are
+more useful).
+
+bitmapPseudoMerge.<name>.stableSize::
+ Determines the size (in number of commits) of a stable
+ psuedo-merge bitmap. The default is `512`.
objects reachable from all of those tags, and answer the query much
faster.
+=== Configuration
+
+Reference tips are grouped into different pseudo-merge groups according
+to two criteria. A reference name matches one or more of the defined
+pseudo-merge patterns, and optionally one or more capture groups within
+that pattern which further partition the group.
+
+Within a group, commits may be considered "stable", or "unstable"
+depending on their age. These are adjusted by setting the
+`bitmapPseudoMerge.<name>.stableThreshold` and
+`bitmapPseudoMerge.<name>.threshold` configuration values, respectively.
+
+All stable commits are grouped into pseudo-merges of equal size
+(`bitmapPseudoMerge.<name>.stableSize`). If the `stableSize`
+configuration is set to, say, 100, then the first 100 commits (ordered
+by committer date) which are older than the `stableThreshold` value will
+form one group, the next 100 commits will form another group, and so on.
+
+Among unstable commits, the pseudo-merge machinery will attempt to
+combine older commits into large groups as opposed to newer commits
+which will appear in smaller groups. This is based on the heuristic that
+references whose tip commit is older are less likely to be modified to
+point at a different commit than a reference whose tip commit is newer.
+
+The size of groups is determined by a power-law decay function, and the
+decay parameter roughly corresponds to "k" in `f(n) = C*n^(-k/100)`,
+where `f(n)` describes the size of the `n`-th pseudo-merge group. The
+sample rate controls what percentage of eligible commits are considered
+as candidates. The threshold parameter indicates the minimum age (so as
+to avoid including too-recent commits in a pseudo-merge group, making it
+less likely to be valid). The "maxMerges" parameter sets an upper-bound
+on the number of pseudo-merge commits an individual group
+
+The "stable"-related parameters control "stable" pseudo-merge groups,
+comprised of a fixed number of commits which are older than the
+configured "stable threshold" value and may be grouped together in
+chunks of "stableSize" in order of age.
+
+The exact configuration for pseudo-merges is as follows:
+
+include::config/bitmap-pseudo-merge.txt[]
+
+=== Examples
+
+Suppose that you have a repository with a large number of references,
+and you want a bare-bones configuration of pseudo-merge bitmaps that
+will enhance bitmap coverage of the `refs/` namespace. You may start
+wiht a configuration like so:
+
+ [bitmapPseudoMerge "all"]
+ pattern = "refs/"
+ threshold = now
+ stableThreshold = never
+ sampleRate = 100
+ maxMerges = 64
+
+This will create pseudo-merge bitmaps for all references, regardless of
+their age, and group them into 64 pseudo-merge commits.
+
+If you wanted to separate tags from branches when generating
+pseudo-merge commits, you would instead define the pattern with a
+capture group, like so:
+
+ [bitmapPseudoMerge "all"]
+ pattern = "refs/(heads/tags)/"
+
+Suppose instead that you are working in a fork-network repository, with
+each fork specified by some numeric ID, and whose refs reside in
+`refs/virtual/NNN/` (where `NNN` is the numeric ID corresponding to some
+fork) in the network. In this instance, you may instead write something
+like:
+
+ [bitmapPseudoMerge "all"]
+ pattern = "refs/virtual/([0-9]+)/(heads|tags)/"
+ threshold = now
+ stableThreshold = never
+ sampleRate = 100
+ maxMerges = 64
+
+Which would generate pseudo-merge group identifiers like "1234-heads",
+and "5678-tags" (for branches in fork "1234", and tags in remote "5678",
+respectively).
+
SEE ALSO
--------
linkgit:git-pack-objects[1]
#include "git-compat-util.h"
#include "pseudo-merge.h"
+#include "date.h"
+#include "oid-array.h"
+#include "strbuf.h"
+#include "config.h"
+#include "string-list.h"
+#include "refs.h"
+#include "pack-bitmap.h"
+#include "commit.h"
+#include "alloc.h"
+#include "progress.h"
+
+#define DEFAULT_PSEUDO_MERGE_DECAY 1.0
+#define DEFAULT_PSEUDO_MERGE_MAX_MERGES 64
+#define DEFAULT_PSEUDO_MERGE_SAMPLE_RATE 1
+#define DEFAULT_PSEUDO_MERGE_THRESHOLD approxidate("1.week.ago")
+#define DEFAULT_PSEUDO_MERGE_STABLE_THRESHOLD approxidate("1.month.ago")
+#define DEFAULT_PSEUDO_MERGE_STABLE_SIZE 512
+
+static double gitexp(double base, int exp)
+{
+ double result = 1;
+ while (1) {
+ if (exp % 2)
+ result *= base;
+ exp >>= 1;
+ if (!exp)
+ break;
+ base *= base;
+ }
+ return result;
+}
+
+static uint32_t pseudo_merge_group_size(const struct pseudo_merge_group *group,
+ const struct pseudo_merge_matches *matches,
+ uint32_t i)
+{
+ double C = 0.0f;
+ uint32_t n;
+
+ /*
+ * The size of pseudo-merge groups decays according to a power series,
+ * which looks like:
+ *
+ * f(n) = C * n^-k
+ *
+ * , where 'n' is the n-th pseudo-merge group, 'f(n)' is its size, 'k'
+ * is the decay rate, and 'C' is a scaling value.
+ *
+ * The value of C depends on the number of groups, decay rate, and total
+ * number of commits. It is computed such that if there are M and N
+ * total groups and commits, respectively, that:
+ *
+ * N = f(0) + f(1) + ... f(M-1)
+ *
+ * Rearranging to isolate C, we get:
+ *
+ * N = \sum_{n=1}^M C / n^k
+ *
+ * N / C = \sum_{n=1}^M n^-k
+ *
+ * C = N / \sum_{n=1}^M n^-k
+ *
+ * For example, if we have a decay rate of 'k' being equal to 1.5, 'N'
+ * total commits equal to 10,000, and 'M' being equal to 6 groups, then
+ * the (rounded) group sizes are:
+ *
+ * { 5469, 1934, 1053, 684, 489, 372 }
+ *
+ * increasing the number of total groups, say to 10, scales the group
+ * sizes appropriately:
+ *
+ * { 5012, 1772, 964, 626, 448, 341, 271, 221, 186, 158 }
+ */
+ for (n = 0; n < group->max_merges; n++)
+ C += 1.0 / gitexp(n + 1, group->decay);
+ C = matches->unstable_nr / C;
+
+ return (uint32_t)((C / gitexp(i + 1, group->decay)) + 0.5);
+}
+
+static void pseudo_merge_group_init(struct pseudo_merge_group *group)
+{
+ memset(group, 0, sizeof(struct pseudo_merge_group));
+
+ strmap_init_with_options(&group->matches, NULL, 0);
+
+ group->decay = DEFAULT_PSEUDO_MERGE_DECAY;
+ group->max_merges = DEFAULT_PSEUDO_MERGE_MAX_MERGES;
+ group->sample_rate = DEFAULT_PSEUDO_MERGE_SAMPLE_RATE;
+ group->threshold = DEFAULT_PSEUDO_MERGE_THRESHOLD;
+ group->stable_threshold = DEFAULT_PSEUDO_MERGE_STABLE_THRESHOLD;
+ group->stable_size = DEFAULT_PSEUDO_MERGE_STABLE_SIZE;
+}
+
+static int pseudo_merge_config(const char *var, const char *value,
+ const struct config_context *ctx,
+ void *cb_data)
+{
+ struct string_list *list = cb_data;
+ struct string_list_item *item;
+ struct pseudo_merge_group *group;
+ struct strbuf buf = STRBUF_INIT;
+ const char *sub, *key;
+ size_t sub_len;
+ int ret = 0;
+
+ if (parse_config_key(var, "bitmappseudomerge", &sub, &sub_len, &key))
+ goto done;
+
+ if (!sub_len)
+ goto done;
+
+ strbuf_add(&buf, sub, sub_len);
+
+ item = string_list_lookup(list, buf.buf);
+ if (!item) {
+ item = string_list_insert(list, buf.buf);
+
+ item->util = xmalloc(sizeof(struct pseudo_merge_group));
+ pseudo_merge_group_init(item->util);
+ }
+
+ group = item->util;
+
+ if (!strcmp(key, "pattern")) {
+ struct strbuf re = STRBUF_INIT;
+
+ free(group->pattern);
+ if (*value != '^')
+ strbuf_addch(&re, '^');
+ strbuf_addstr(&re, value);
+
+ group->pattern = xcalloc(1, sizeof(regex_t));
+ if (regcomp(group->pattern, re.buf, REG_EXTENDED))
+ die(_("failed to load pseudo-merge regex for %s: '%s'"),
+ sub, re.buf);
+
+ strbuf_release(&re);
+ } else if (!strcmp(key, "decay")) {
+ group->decay = git_config_double(var, value, ctx->kvi);
+ if (group->decay < 0) {
+ warning(_("%s must be non-negative, using default"), var);
+ group->decay = DEFAULT_PSEUDO_MERGE_DECAY;
+ }
+ } else if (!strcmp(key, "samplerate")) {
+ group->sample_rate = git_config_double(var, value, ctx->kvi);
+ if (!(0 <= group->sample_rate && group->sample_rate <= 1)) {
+ warning(_("%s must be between 0 and 1, using default"), var);
+ group->sample_rate = DEFAULT_PSEUDO_MERGE_SAMPLE_RATE;
+ }
+ } else if (!strcmp(key, "threshold")) {
+ if (git_config_expiry_date(&group->threshold, var, value)) {
+ ret = -1;
+ goto done;
+ }
+ } else if (!strcmp(key, "maxmerges")) {
+ group->max_merges = git_config_int(var, value, ctx->kvi);
+ if (group->max_merges < 0) {
+ warning(_("%s must be non-negative, using default"), var);
+ group->max_merges = DEFAULT_PSEUDO_MERGE_MAX_MERGES;
+ }
+ } else if (!strcmp(key, "stablethreshold")) {
+ if (git_config_expiry_date(&group->stable_threshold, var, value)) {
+ ret = -1;
+ goto done;
+ }
+ } else if (!strcmp(key, "stablesize")) {
+ group->stable_size = git_config_int(var, value, ctx->kvi);
+ if (group->stable_size <= 0) {
+ warning(_("%s must be positive, using default"), var);
+ group->stable_size = DEFAULT_PSEUDO_MERGE_STABLE_SIZE;
+ }
+ }
+
+done:
+ strbuf_release(&buf);
+
+ return ret;
+}
+
+void load_pseudo_merges_from_config(struct string_list *list)
+{
+ struct string_list_item *item;
+
+ git_config(pseudo_merge_config, list);
+
+ for_each_string_list_item(item, list) {
+ struct pseudo_merge_group *group = item->util;
+ if (!group->pattern)
+ die(_("pseudo-merge group '%s' missing required pattern"),
+ item->string);
+ if (group->threshold < group->stable_threshold)
+ die(_("pseudo-merge group '%s' has unstable threshold "
+ "before stable one"), item->string);
+ }
+}
+
+static int find_pseudo_merge_group_for_ref(const char *refname,
+ const struct object_id *oid,
+ int flags UNUSED,
+ void *_data)
+{
+ struct bitmap_writer *writer = _data;
+ struct object_id peeled;
+ struct commit *c;
+ uint32_t i;
+ int has_bitmap;
+
+ if (!peel_iterated_oid(oid, &peeled))
+ oid = &peeled;
+
+ c = lookup_commit(the_repository, oid);
+ if (!c)
+ return 0;
+
+ has_bitmap = bitmap_writer_has_bitmapped_object_id(writer, oid);
+
+ for (i = 0; i < writer->pseudo_merge_groups.nr; i++) {
+ struct pseudo_merge_group *group;
+ struct pseudo_merge_matches *matches;
+ struct strbuf group_name = STRBUF_INIT;
+ regmatch_t captures[16];
+ size_t j;
+
+ group = writer->pseudo_merge_groups.items[i].util;
+ if (regexec(group->pattern, refname, ARRAY_SIZE(captures),
+ captures, 0))
+ continue;
+
+ if (captures[ARRAY_SIZE(captures) - 1].rm_so != -1)
+ warning(_("pseudo-merge regex from config has too many capture "
+ "groups (max=%"PRIuMAX")"),
+ (uintmax_t)ARRAY_SIZE(captures) - 2);
+
+ for (j = !!group->pattern->re_nsub; j < ARRAY_SIZE(captures); j++) {
+ regmatch_t *match = &captures[j];
+ if (match->rm_so == -1)
+ continue;
+
+ if (group_name.len)
+ strbuf_addch(&group_name, '-');
+
+ strbuf_add(&group_name, refname + match->rm_so,
+ match->rm_eo - match->rm_so);
+ }
+
+ matches = strmap_get(&group->matches, group_name.buf);
+ if (!matches) {
+ matches = xcalloc(1, sizeof(*matches));
+ strmap_put(&group->matches, strbuf_detach(&group_name, NULL),
+ matches);
+ }
+
+ if (c->date <= group->stable_threshold) {
+ ALLOC_GROW(matches->stable, matches->stable_nr + 1,
+ matches->stable_alloc);
+ matches->stable[matches->stable_nr++] = c;
+ } else if (c->date <= group->threshold && !has_bitmap) {
+ ALLOC_GROW(matches->unstable, matches->unstable_nr + 1,
+ matches->unstable_alloc);
+ matches->unstable[matches->unstable_nr++] = c;
+ }
+
+ strbuf_release(&group_name);
+ }
+
+ return 0;
+}
+
+static struct commit *push_pseudo_merge(struct pseudo_merge_group *group)
+{
+ struct commit *merge;
+
+ ALLOC_GROW(group->merges, group->merges_nr + 1, group->merges_alloc);
+
+ merge = alloc_commit_node(the_repository);
+ merge->object.parsed = 1;
+ merge->object.flags |= BITMAP_PSEUDO_MERGE;
+
+ group->merges[group->merges_nr++] = merge;
+
+ return merge;
+}
+
+static struct pseudo_merge_commit_idx *pseudo_merge_idx(kh_oid_map_t *pseudo_merge_commits,
+ const struct object_id *oid)
+
+{
+ struct pseudo_merge_commit_idx *pmc;
+ int hash_ret;
+ khiter_t hash_pos = kh_put_oid_map(pseudo_merge_commits, *oid,
+ &hash_ret);
+
+ if (hash_ret) {
+ CALLOC_ARRAY(pmc, 1);
+ kh_value(pseudo_merge_commits, hash_pos) = pmc;
+ } else {
+ pmc = kh_value(pseudo_merge_commits, hash_pos);
+ }
+
+ return pmc;
+}
+
+#define MIN_PSEUDO_MERGE_SIZE 8
+
+static void select_pseudo_merges_1(struct bitmap_writer *writer,
+ struct pseudo_merge_group *group,
+ struct pseudo_merge_matches *matches)
+{
+ uint32_t i, j;
+ uint32_t stable_merges_nr;
+
+ if (!matches->stable_nr && !matches->unstable_nr)
+ return; /* all tips in this group already have bitmaps */
+
+ stable_merges_nr = matches->stable_nr / group->stable_size;
+ if (matches->stable_nr % group->stable_size)
+ stable_merges_nr++;
+
+ /* make stable_merges_nr pseudo merges for stable commits */
+ for (i = 0, j = 0; i < stable_merges_nr; i++) {
+ struct commit *merge;
+ struct commit_list **p;
+
+ merge = push_pseudo_merge(group);
+ p = &merge->parents;
+
+ /*
+ * For each pseudo-merge created above, add parents to the
+ * allocated commit node from the stable set of commits
+ * (un-bitmapped, newer than the stable threshold).
+ */
+ do {
+ struct commit *c;
+ struct pseudo_merge_commit_idx *pmc;
+
+ if (j >= matches->stable_nr)
+ break;
+
+ c = matches->stable[j++];
+ /*
+ * Here and below, make sure that we keep our mapping of
+ * commits -> pseudo-merge(s) which include the key'd
+ * commit up-to-date.
+ */
+ pmc = pseudo_merge_idx(writer->pseudo_merge_commits,
+ &c->object.oid);
+
+ ALLOC_GROW(pmc->pseudo_merge, pmc->nr + 1, pmc->alloc);
+
+ pmc->pseudo_merge[pmc->nr++] = writer->pseudo_merges_nr;
+ p = commit_list_append(c, p);
+ } while (j % group->stable_size);
+
+ bitmap_writer_push_commit(writer, merge, 1);
+ writer->pseudo_merges_nr++;
+ }
+
+ /* make up to group->max_merges pseudo merges for unstable commits */
+ for (i = 0, j = 0; i < group->max_merges; i++) {
+ struct commit *merge;
+ struct commit_list **p;
+ uint32_t size, end;
+
+ merge = push_pseudo_merge(group);
+ p = &merge->parents;
+
+ size = pseudo_merge_group_size(group, matches, i);
+ end = size < MIN_PSEUDO_MERGE_SIZE ? matches->unstable_nr : j + size;
+
+ /*
+ * For each pseudo-merge commit created above, add parents to
+ * the allocated commit node from the unstable set of commits
+ * (newer than the stable threshold).
+ *
+ * Account for the sample rate, since not every candidate from
+ * the set of stable commits will be included as a pseudo-merge
+ * parent.
+ */
+ for (; j < end && j < matches->unstable_nr; j++) {
+ struct commit *c = matches->unstable[j];
+ struct pseudo_merge_commit_idx *pmc;
+
+ if (j % (uint32_t)(1.0 / group->sample_rate))
+ continue;
+
+ pmc = pseudo_merge_idx(writer->pseudo_merge_commits,
+ &c->object.oid);
+
+ ALLOC_GROW(pmc->pseudo_merge, pmc->nr + 1, pmc->alloc);
+
+ pmc->pseudo_merge[pmc->nr++] = writer->pseudo_merges_nr;
+ p = commit_list_append(c, p);
+ }
+
+ bitmap_writer_push_commit(writer, merge, 1);
+ writer->pseudo_merges_nr++;
+ if (end >= matches->unstable_nr)
+ break;
+ }
+}
+
+static int commit_date_cmp(const void *va, const void *vb)
+{
+ timestamp_t a = (*(const struct commit **)va)->date;
+ timestamp_t b = (*(const struct commit **)vb)->date;
+
+ if (a < b)
+ return -1;
+ else if (a > b)
+ return 1;
+ return 0;
+}
+
+static void sort_pseudo_merge_matches(struct pseudo_merge_matches *matches)
+{
+ QSORT(matches->stable, matches->stable_nr, commit_date_cmp);
+ QSORT(matches->unstable, matches->unstable_nr, commit_date_cmp);
+}
+
+void select_pseudo_merges(struct bitmap_writer *writer,
+ struct commit **commits, size_t commits_nr)
+{
+ struct progress *progress = NULL;
+ uint32_t i;
+
+ if (!writer->pseudo_merge_groups.nr)
+ return;
+
+ if (writer->show_progress)
+ progress = start_progress("Selecting pseudo-merge commits",
+ writer->pseudo_merge_groups.nr);
+
+ for_each_ref(find_pseudo_merge_group_for_ref, writer);
+
+ for (i = 0; i < writer->pseudo_merge_groups.nr; i++) {
+ struct pseudo_merge_group *group;
+ struct hashmap_iter iter;
+ struct strmap_entry *e;
+
+ group = writer->pseudo_merge_groups.items[i].util;
+ strmap_for_each_entry(&group->matches, &iter, e) {
+ struct pseudo_merge_matches *matches = e->value;
+
+ sort_pseudo_merge_matches(matches);
+
+ select_pseudo_merges_1(writer, group, matches);
+ }
+
+ display_progress(progress, i + 1);
+ }
+
+ stop_progress(&progress);
+}
projects / thirdparty / git.git / commitdiff
