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authorJunio C Hamano <gitster@pobox.com>2018-08-02 22:30:46 (GMT)
committerJunio C Hamano <gitster@pobox.com>2018-08-02 22:30:46 (GMT)
commit7c85ee6c5818f4409a29e40cc406ef5db9560af8 (patch)
tree3ae0b2267d235f9bf4f81dd1a7d781e980a953ce /negotiator
parentd6873a396e054d814744f8943fd1c343ecf4a9dc (diff)
parent42cc7485a2ec49ecc440c921d2eb0cae4da80549 (diff)
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Merge branch 'jt/fetch-negotiator-skipping'
Add a server-side knob to skip commits in exponential/fibbonacci stride in an attempt to cover wider swath of history with a smaller number of iterations, potentially accepting a larger packfile transfer, instead of going back one commit a time during common ancestor discovery during the "git fetch" transaction. * jt/fetch-negotiator-skipping: negotiator/skipping: skip commits during fetch
Diffstat (limited to 'negotiator')
-rw-r--r--negotiator/skipping.c250
-rw-r--r--negotiator/skipping.h8
2 files changed, 258 insertions, 0 deletions
diff --git a/negotiator/skipping.c b/negotiator/skipping.c
new file mode 100644
index 0000000..dffbc76
--- /dev/null
+++ b/negotiator/skipping.c
@@ -0,0 +1,250 @@
+#include "cache.h"
+#include "skipping.h"
+#include "../commit.h"
+#include "../fetch-negotiator.h"
+#include "../prio-queue.h"
+#include "../refs.h"
+#include "../tag.h"
+
+/* Remember to update object flag allocation in object.h */
+/*
+ * Both us and the server know that both parties have this object.
+ */
+#define COMMON (1U << 2)
+/*
+ * The server has told us that it has this object. We still need to tell the
+ * server that we have this object (or one of its descendants), but since we are
+ * going to do that, we do not need to tell the server about its ancestors.
+ */
+#define ADVERTISED (1U << 3)
+/*
+ * This commit has entered the priority queue.
+ */
+#define SEEN (1U << 4)
+/*
+ * This commit has left the priority queue.
+ */
+#define POPPED (1U << 5)
+
+static int marked;
+
+/*
+ * An entry in the priority queue.
+ */
+struct entry {
+ struct commit *commit;
+
+ /*
+ * Used only if commit is not COMMON.
+ */
+ uint16_t original_ttl;
+ uint16_t ttl;
+};
+
+struct data {
+ struct prio_queue rev_list;
+
+ /*
+ * The number of non-COMMON commits in rev_list.
+ */
+ int non_common_revs;
+};
+
+static int compare(const void *a_, const void *b_, void *unused)
+{
+ const struct entry *a = a_;
+ const struct entry *b = b_;
+ return compare_commits_by_commit_date(a->commit, b->commit, NULL);
+}
+
+static struct entry *rev_list_push(struct data *data, struct commit *commit, int mark)
+{
+ struct entry *entry;
+ commit->object.flags |= mark | SEEN;
+
+ entry = xcalloc(1, sizeof(*entry));
+ entry->commit = commit;
+ prio_queue_put(&data->rev_list, entry);
+
+ if (!(mark & COMMON))
+ data->non_common_revs++;
+ return entry;
+}
+
+static int clear_marks(const char *refname, const struct object_id *oid,
+ int flag, void *cb_data)
+{
+ struct object *o = deref_tag(the_repository, parse_object(the_repository, oid), refname, 0);
+
+ if (o && o->type == OBJ_COMMIT)
+ clear_commit_marks((struct commit *)o,
+ COMMON | ADVERTISED | SEEN | POPPED);
+ return 0;
+}
+
+/*
+ * Mark this SEEN commit and all its SEEN ancestors as COMMON.
+ */
+static void mark_common(struct data *data, struct commit *c)
+{
+ struct commit_list *p;
+
+ if (c->object.flags & COMMON)
+ return;
+ c->object.flags |= COMMON;
+ if (!(c->object.flags & POPPED))
+ data->non_common_revs--;
+
+ if (!c->object.parsed)
+ return;
+ for (p = c->parents; p; p = p->next) {
+ if (p->item->object.flags & SEEN)
+ mark_common(data, p->item);
+ }
+}
+
+/*
+ * Ensure that the priority queue has an entry for to_push, and ensure that the
+ * entry has the correct flags and ttl.
+ *
+ * This function returns 1 if an entry was found or created, and 0 otherwise
+ * (because the entry for this commit had already been popped).
+ */
+static int push_parent(struct data *data, struct entry *entry,
+ struct commit *to_push)
+{
+ struct entry *parent_entry;
+
+ if (to_push->object.flags & SEEN) {
+ int i;
+ if (to_push->object.flags & POPPED)
+ /*
+ * The entry for this commit has already been popped,
+ * due to clock skew. Pretend that this parent does not
+ * exist.
+ */
+ return 0;
+ /*
+ * Find the existing entry and use it.
+ */
+ for (i = 0; i < data->rev_list.nr; i++) {
+ parent_entry = data->rev_list.array[i].data;
+ if (parent_entry->commit == to_push)
+ goto parent_found;
+ }
+ BUG("missing parent in priority queue");
+parent_found:
+ ;
+ } else {
+ parent_entry = rev_list_push(data, to_push, 0);
+ }
+
+ if (entry->commit->object.flags & (COMMON | ADVERTISED)) {
+ mark_common(data, to_push);
+ } else {
+ uint16_t new_original_ttl = entry->ttl
+ ? entry->original_ttl : entry->original_ttl * 3 / 2 + 1;
+ uint16_t new_ttl = entry->ttl
+ ? entry->ttl - 1 : new_original_ttl;
+ if (parent_entry->original_ttl < new_original_ttl) {
+ parent_entry->original_ttl = new_original_ttl;
+ parent_entry->ttl = new_ttl;
+ }
+ }
+
+ return 1;
+}
+
+static const struct object_id *get_rev(struct data *data)
+{
+ struct commit *to_send = NULL;
+
+ while (to_send == NULL) {
+ struct entry *entry;
+ struct commit *commit;
+ struct commit_list *p;
+ int parent_pushed = 0;
+
+ if (data->rev_list.nr == 0 || data->non_common_revs == 0)
+ return NULL;
+
+ entry = prio_queue_get(&data->rev_list);
+ commit = entry->commit;
+ commit->object.flags |= POPPED;
+ if (!(commit->object.flags & COMMON))
+ data->non_common_revs--;
+
+ if (!(commit->object.flags & COMMON) && !entry->ttl)
+ to_send = commit;
+
+ parse_commit(commit);
+ for (p = commit->parents; p; p = p->next)
+ parent_pushed |= push_parent(data, entry, p->item);
+
+ if (!(commit->object.flags & COMMON) && !parent_pushed)
+ /*
+ * This commit has no parents, or all of its parents
+ * have already been popped (due to clock skew), so send
+ * it anyway.
+ */
+ to_send = commit;
+
+ free(entry);
+ }
+
+ return &to_send->object.oid;
+}
+
+static void known_common(struct fetch_negotiator *n, struct commit *c)
+{
+ if (c->object.flags & SEEN)
+ return;
+ rev_list_push(n->data, c, ADVERTISED);
+}
+
+static void add_tip(struct fetch_negotiator *n, struct commit *c)
+{
+ n->known_common = NULL;
+ if (c->object.flags & SEEN)
+ return;
+ rev_list_push(n->data, c, 0);
+}
+
+static const struct object_id *next(struct fetch_negotiator *n)
+{
+ n->known_common = NULL;
+ n->add_tip = NULL;
+ return get_rev(n->data);
+}
+
+static int ack(struct fetch_negotiator *n, struct commit *c)
+{
+ int known_to_be_common = !!(c->object.flags & COMMON);
+ if (!(c->object.flags & SEEN))
+ die("received ack for commit %s not sent as 'have'\n",
+ oid_to_hex(&c->object.oid));
+ mark_common(n->data, c);
+ return known_to_be_common;
+}
+
+static void release(struct fetch_negotiator *n)
+{
+ clear_prio_queue(&((struct data *)n->data)->rev_list);
+ FREE_AND_NULL(n->data);
+}
+
+void skipping_negotiator_init(struct fetch_negotiator *negotiator)
+{
+ struct data *data;
+ negotiator->known_common = known_common;
+ negotiator->add_tip = add_tip;
+ negotiator->next = next;
+ negotiator->ack = ack;
+ negotiator->release = release;
+ negotiator->data = data = xcalloc(1, sizeof(*data));
+ data->rev_list.compare = compare;
+
+ if (marked)
+ for_each_ref(clear_marks, NULL);
+ marked = 1;
+}
diff --git a/negotiator/skipping.h b/negotiator/skipping.h
new file mode 100644
index 0000000..d7dfa6c
--- /dev/null
+++ b/negotiator/skipping.h
@@ -0,0 +1,8 @@
+#ifndef NEGOTIATOR_SKIPPING_H
+#define NEGOTIATOR_SKIPPING_H
+
+struct fetch_negotiator;
+
+void skipping_negotiator_init(struct fetch_negotiator *negotiator);
+
+#endif