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authorJunio C Hamano <gitster@pobox.com>2018-09-17 20:53:55 (GMT)
committerJunio C Hamano <gitster@pobox.com>2018-09-17 20:53:55 (GMT)
commitf3504ea3dd21b0a6d38bcd369efa0663cdc05416 (patch)
treec8eb1191474dc37e25f082917e803915525c15d1
parentfba9654364a523bf146df26052ab05dd52c1d719 (diff)
parentfe0ac2fb7f8e87d37ef83dcee2d93901d58d8277 (diff)
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Merge branch 'cc/delta-islands'
Lift code from GitHub to restrict delta computation so that an object that exists in one fork is not made into a delta against another object that does not appear in the same forked repository. * cc/delta-islands: pack-objects: move 'layer' into 'struct packing_data' pack-objects: move tree_depth into 'struct packing_data' t5320: tests for delta islands repack: add delta-islands support pack-objects: add delta-islands support pack-objects: refactor code into compute_layer_order() Add delta-islands.{c,h}
-rw-r--r--Documentation/config.txt19
-rw-r--r--Documentation/git-pack-objects.txt97
-rw-r--r--Documentation/git-repack.txt5
-rw-r--r--Makefile1
-rw-r--r--builtin/pack-objects.c137
-rw-r--r--builtin/repack.c9
-rw-r--r--delta-islands.c502
-rw-r--r--delta-islands.h11
-rw-r--r--pack-objects.c12
-rw-r--r--pack-objects.h39
-rwxr-xr-xt/t5320-delta-islands.sh143
11 files changed, 932 insertions, 43 deletions
diff --git a/Documentation/config.txt b/Documentation/config.txt
index 6ecd70d..112041f 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -2684,6 +2684,21 @@ Note that changing the compression level will not automatically recompress
all existing objects. You can force recompression by passing the -F option
to linkgit:git-repack[1].
+pack.island::
+ An extended regular expression configuring a set of delta
+ islands. See "DELTA ISLANDS" in linkgit:git-pack-objects[1]
+ for details.
+
+pack.islandCore::
+ Specify an island name which gets to have its objects be
+ packed first. This creates a kind of pseudo-pack at the front
+ of one pack, so that the objects from the specified island are
+ hopefully faster to copy into any pack that should be served
+ to a user requesting these objects. In practice this means
+ that the island specified should likely correspond to what is
+ the most commonly cloned in the repo. See also "DELTA ISLANDS"
+ in linkgit:git-pack-objects[1].
+
pack.deltaCacheSize::
The maximum memory in bytes used for caching deltas in
linkgit:git-pack-objects[1] before writing them out to a pack.
@@ -3218,6 +3233,10 @@ repack.packKeptObjects::
index is being written (either via `--write-bitmap-index` or
`repack.writeBitmaps`).
+repack.useDeltaIslands::
+ If set to true, makes `git repack` act as if `--delta-islands`
+ was passed. Defaults to `false`.
+
repack.writeBitmaps::
When true, git will write a bitmap index when packing all
objects to disk (e.g., when `git repack -a` is run). This
diff --git a/Documentation/git-pack-objects.txt b/Documentation/git-pack-objects.txt
index d95b472..40c825c 100644
--- a/Documentation/git-pack-objects.txt
+++ b/Documentation/git-pack-objects.txt
@@ -289,6 +289,103 @@ Unexpected missing object will raise an error.
--unpack-unreachable::
Keep unreachable objects in loose form. This implies `--revs`.
+--delta-islands::
+ Restrict delta matches based on "islands". See DELTA ISLANDS
+ below.
+
+
+DELTA ISLANDS
+-------------
+
+When possible, `pack-objects` tries to reuse existing on-disk deltas to
+avoid having to search for new ones on the fly. This is an important
+optimization for serving fetches, because it means the server can avoid
+inflating most objects at all and just send the bytes directly from
+disk. This optimization can't work when an object is stored as a delta
+against a base which the receiver does not have (and which we are not
+already sending). In that case the server "breaks" the delta and has to
+find a new one, which has a high CPU cost. Therefore it's important for
+performance that the set of objects in on-disk delta relationships match
+what a client would fetch.
+
+In a normal repository, this tends to work automatically. The objects
+are mostly reachable from the branches and tags, and that's what clients
+fetch. Any deltas we find on the server are likely to be between objects
+the client has or will have.
+
+But in some repository setups, you may have several related but separate
+groups of ref tips, with clients tending to fetch those groups
+independently. For example, imagine that you are hosting several "forks"
+of a repository in a single shared object store, and letting clients
+view them as separate repositories through `GIT_NAMESPACE` or separate
+repos using the alternates mechanism. A naive repack may find that the
+optimal delta for an object is against a base that is only found in
+another fork. But when a client fetches, they will not have the base
+object, and we'll have to find a new delta on the fly.
+
+A similar situation may exist if you have many refs outside of
+`refs/heads/` and `refs/tags/` that point to related objects (e.g.,
+`refs/pull` or `refs/changes` used by some hosting providers). By
+default, clients fetch only heads and tags, and deltas against objects
+found only in those other groups cannot be sent as-is.
+
+Delta islands solve this problem by allowing you to group your refs into
+distinct "islands". Pack-objects computes which objects are reachable
+from which islands, and refuses to make a delta from an object `A`
+against a base which is not present in all of `A`'s islands. This
+results in slightly larger packs (because we miss some delta
+opportunities), but guarantees that a fetch of one island will not have
+to recompute deltas on the fly due to crossing island boundaries.
+
+When repacking with delta islands the delta window tends to get
+clogged with candidates that are forbidden by the config. Repacking
+with a big --window helps (and doesn't take as long as it otherwise
+might because we can reject some object pairs based on islands before
+doing any computation on the content).
+
+Islands are configured via the `pack.island` option, which can be
+specified multiple times. Each value is a left-anchored regular
+expressions matching refnames. For example:
+
+-------------------------------------------
+[pack]
+island = refs/heads/
+island = refs/tags/
+-------------------------------------------
+
+puts heads and tags into an island (whose name is the empty string; see
+below for more on naming). Any refs which do not match those regular
+expressions (e.g., `refs/pull/123`) is not in any island. Any object
+which is reachable only from `refs/pull/` (but not heads or tags) is
+therefore not a candidate to be used as a base for `refs/heads/`.
+
+Refs are grouped into islands based on their "names", and two regexes
+that produce the same name are considered to be in the same
+island. The names are computed from the regexes by concatenating any
+capture groups from the regex, with a '-' dash in between. (And if
+there are no capture groups, then the name is the empty string, as in
+the above example.) This allows you to create arbitrary numbers of
+islands. Only up to 14 such capture groups are supported though.
+
+For example, imagine you store the refs for each fork in
+`refs/virtual/ID`, where `ID` is a numeric identifier. You might then
+configure:
+
+-------------------------------------------
+[pack]
+island = refs/virtual/([0-9]+)/heads/
+island = refs/virtual/([0-9]+)/tags/
+island = refs/virtual/([0-9]+)/(pull)/
+-------------------------------------------
+
+That puts the heads and tags for each fork in their own island (named
+"1234" or similar), and the pull refs for each go into their own
+"1234-pull".
+
+Note that we pick a single island for each regex to go into, using "last
+one wins" ordering (which allows repo-specific config to take precedence
+over user-wide config, and so forth).
+
SEE ALSO
--------
linkgit:git-rev-list[1]
diff --git a/Documentation/git-repack.txt b/Documentation/git-repack.txt
index d056250..aa0cc8b 100644
--- a/Documentation/git-repack.txt
+++ b/Documentation/git-repack.txt
@@ -160,6 +160,11 @@ depth is 4095.
being removed. In addition, any unreachable loose objects will
be packed (and their loose counterparts removed).
+-i::
+--delta-islands::
+ Pass the `--delta-islands` option to `git-pack-objects`, see
+ linkgit:git-pack-objects[1].
+
Configuration
-------------
diff --git a/Makefile b/Makefile
index d6cd9a5..7cf6820 100644
--- a/Makefile
+++ b/Makefile
@@ -850,6 +850,7 @@ LIB_OBJS += csum-file.o
LIB_OBJS += ctype.o
LIB_OBJS += date.o
LIB_OBJS += decorate.o
+LIB_OBJS += delta-islands.o
LIB_OBJS += diffcore-break.o
LIB_OBJS += diffcore-delta.o
LIB_OBJS += diffcore-order.o
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index f434e1f..425bdc8 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -24,6 +24,7 @@
#include "streaming.h"
#include "thread-utils.h"
#include "pack-bitmap.h"
+#include "delta-islands.h"
#include "reachable.h"
#include "sha1-array.h"
#include "argv-array.h"
@@ -62,6 +63,7 @@ static struct packing_data to_pack;
static struct pack_idx_entry **written_list;
static uint32_t nr_result, nr_written, nr_seen;
static struct bitmap_index *bitmap_git;
+static uint32_t write_layer;
static int non_empty;
static int reuse_delta = 1, reuse_object = 1;
@@ -97,6 +99,8 @@ static uint16_t write_bitmap_options;
static int exclude_promisor_objects;
+static int use_delta_islands;
+
static unsigned long delta_cache_size = 0;
static unsigned long max_delta_cache_size = DEFAULT_DELTA_CACHE_SIZE;
static unsigned long cache_max_small_delta_size = 1000;
@@ -616,7 +620,7 @@ static inline void add_to_write_order(struct object_entry **wo,
unsigned int *endp,
struct object_entry *e)
{
- if (e->filled)
+ if (e->filled || oe_layer(&to_pack, e) != write_layer)
return;
wo[(*endp)++] = e;
e->filled = 1;
@@ -676,48 +680,15 @@ static void add_family_to_write_order(struct object_entry **wo,
add_descendants_to_write_order(wo, endp, root);
}
-static struct object_entry **compute_write_order(void)
+static void compute_layer_order(struct object_entry **wo, unsigned int *wo_end)
{
- unsigned int i, wo_end, last_untagged;
-
- struct object_entry **wo;
+ unsigned int i, last_untagged;
struct object_entry *objects = to_pack.objects;
for (i = 0; i < to_pack.nr_objects; i++) {
- objects[i].tagged = 0;
- objects[i].filled = 0;
- SET_DELTA_CHILD(&objects[i], NULL);
- SET_DELTA_SIBLING(&objects[i], NULL);
- }
-
- /*
- * Fully connect delta_child/delta_sibling network.
- * Make sure delta_sibling is sorted in the original
- * recency order.
- */
- for (i = to_pack.nr_objects; i > 0;) {
- struct object_entry *e = &objects[--i];
- if (!DELTA(e))
- continue;
- /* Mark me as the first child */
- e->delta_sibling_idx = DELTA(e)->delta_child_idx;
- SET_DELTA_CHILD(DELTA(e), e);
- }
-
- /*
- * Mark objects that are at the tip of tags.
- */
- for_each_tag_ref(mark_tagged, NULL);
-
- /*
- * Give the objects in the original recency order until
- * we see a tagged tip.
- */
- ALLOC_ARRAY(wo, to_pack.nr_objects);
- for (i = wo_end = 0; i < to_pack.nr_objects; i++) {
if (objects[i].tagged)
break;
- add_to_write_order(wo, &wo_end, &objects[i]);
+ add_to_write_order(wo, wo_end, &objects[i]);
}
last_untagged = i;
@@ -726,7 +697,7 @@ static struct object_entry **compute_write_order(void)
*/
for (; i < to_pack.nr_objects; i++) {
if (objects[i].tagged)
- add_to_write_order(wo, &wo_end, &objects[i]);
+ add_to_write_order(wo, wo_end, &objects[i]);
}
/*
@@ -736,7 +707,7 @@ static struct object_entry **compute_write_order(void)
if (oe_type(&objects[i]) != OBJ_COMMIT &&
oe_type(&objects[i]) != OBJ_TAG)
continue;
- add_to_write_order(wo, &wo_end, &objects[i]);
+ add_to_write_order(wo, wo_end, &objects[i]);
}
/*
@@ -745,17 +716,61 @@ static struct object_entry **compute_write_order(void)
for (i = last_untagged; i < to_pack.nr_objects; i++) {
if (oe_type(&objects[i]) != OBJ_TREE)
continue;
- add_to_write_order(wo, &wo_end, &objects[i]);
+ add_to_write_order(wo, wo_end, &objects[i]);
}
/*
* Finally all the rest in really tight order
*/
for (i = last_untagged; i < to_pack.nr_objects; i++) {
- if (!objects[i].filled)
- add_family_to_write_order(wo, &wo_end, &objects[i]);
+ if (!objects[i].filled && oe_layer(&to_pack, &objects[i]) == write_layer)
+ add_family_to_write_order(wo, wo_end, &objects[i]);
+ }
+}
+
+static struct object_entry **compute_write_order(void)
+{
+ uint32_t max_layers = 1;
+ unsigned int i, wo_end;
+
+ struct object_entry **wo;
+ struct object_entry *objects = to_pack.objects;
+
+ for (i = 0; i < to_pack.nr_objects; i++) {
+ objects[i].tagged = 0;
+ objects[i].filled = 0;
+ SET_DELTA_CHILD(&objects[i], NULL);
+ SET_DELTA_SIBLING(&objects[i], NULL);
+ }
+
+ /*
+ * Fully connect delta_child/delta_sibling network.
+ * Make sure delta_sibling is sorted in the original
+ * recency order.
+ */
+ for (i = to_pack.nr_objects; i > 0;) {
+ struct object_entry *e = &objects[--i];
+ if (!DELTA(e))
+ continue;
+ /* Mark me as the first child */
+ e->delta_sibling_idx = DELTA(e)->delta_child_idx;
+ SET_DELTA_CHILD(DELTA(e), e);
}
+ /*
+ * Mark objects that are at the tip of tags.
+ */
+ for_each_tag_ref(mark_tagged, NULL);
+
+ if (use_delta_islands)
+ max_layers = compute_pack_layers(&to_pack);
+
+ ALLOC_ARRAY(wo, to_pack.nr_objects);
+ wo_end = 0;
+
+ for (; write_layer < max_layers; ++write_layer)
+ compute_layer_order(wo, &wo_end);
+
if (wo_end != to_pack.nr_objects)
die(_("ordered %u objects, expected %"PRIu32),
wo_end, to_pack.nr_objects);
@@ -1544,7 +1559,8 @@ static void check_object(struct object_entry *entry)
if (base_ref && (
(base_entry = packlist_find(&to_pack, base_ref, NULL)) ||
(thin &&
- bitmap_has_sha1_in_uninteresting(bitmap_git, base_ref)))) {
+ bitmap_has_sha1_in_uninteresting(bitmap_git, base_ref))) &&
+ in_same_island(&entry->idx.oid, &base_entry->idx.oid)) {
/*
* If base_ref was set above that means we wish to
* reuse delta data, and either we found that object in
@@ -1867,6 +1883,11 @@ static int type_size_sort(const void *_a, const void *_b)
return -1;
if (a->preferred_base < b->preferred_base)
return 1;
+ if (use_delta_islands) {
+ int island_cmp = island_delta_cmp(&a->idx.oid, &b->idx.oid);
+ if (island_cmp)
+ return island_cmp;
+ }
if (a_size > b_size)
return -1;
if (a_size < b_size)
@@ -2027,6 +2048,9 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,
if (trg_size < src_size / 32)
return 0;
+ if (!in_same_island(&trg->entry->idx.oid, &src->entry->idx.oid))
+ return 0;
+
/* Load data if not already done */
if (!trg->data) {
read_lock();
@@ -2569,6 +2593,9 @@ static void prepare_pack(int window, int depth)
uint32_t i, nr_deltas;
unsigned n;
+ if (use_delta_islands)
+ resolve_tree_islands(progress, &to_pack);
+
get_object_details();
/*
@@ -2732,6 +2759,9 @@ static void show_commit(struct commit *commit, void *data)
if (write_bitmap_index)
index_commit_for_bitmap(commit);
+
+ if (use_delta_islands)
+ propagate_island_marks(commit);
}
static void show_object(struct object *obj, const char *name, void *data)
@@ -2739,6 +2769,19 @@ static void show_object(struct object *obj, const char *name, void *data)
add_preferred_base_object(name);
add_object_entry(&obj->oid, obj->type, name, 0);
obj->flags |= OBJECT_ADDED;
+
+ if (use_delta_islands) {
+ const char *p;
+ unsigned depth = 0;
+ struct object_entry *ent;
+
+ for (p = strchr(name, '/'); p; p = strchr(p + 1, '/'))
+ depth++;
+
+ ent = packlist_find(&to_pack, obj->oid.hash, NULL);
+ if (ent && depth > oe_tree_depth(&to_pack, ent))
+ oe_set_tree_depth(&to_pack, ent, depth);
+ }
}
static void show_object__ma_allow_any(struct object *obj, const char *name, void *data)
@@ -3064,6 +3107,9 @@ static void get_object_list(int ac, const char **av)
if (use_bitmap_index && !get_object_list_from_bitmap(&revs))
return;
+ if (use_delta_islands)
+ load_delta_islands();
+
if (prepare_revision_walk(&revs))
die(_("revision walk setup failed"));
mark_edges_uninteresting(&revs, show_edge);
@@ -3242,6 +3288,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
option_parse_missing_action },
OPT_BOOL(0, "exclude-promisor-objects", &exclude_promisor_objects,
N_("do not pack objects in promisor packfiles")),
+ OPT_BOOL(0, "delta-islands", &use_delta_islands,
+ N_("respect islands during delta compression")),
OPT_END(),
};
@@ -3368,6 +3416,9 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
if (pack_to_stdout || !rev_list_all)
write_bitmap_index = 0;
+ if (use_delta_islands)
+ argv_array_push(&rp, "--topo-order");
+
if (progress && all_progress_implied)
progress = 2;
diff --git a/builtin/repack.c b/builtin/repack.c
index 42be88e..c6a7943 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -15,6 +15,7 @@
static int delta_base_offset = 1;
static int pack_kept_objects = -1;
static int write_bitmaps;
+static int use_delta_islands;
static char *packdir, *packtmp;
static const char *const git_repack_usage[] = {
@@ -43,6 +44,10 @@ static int repack_config(const char *var, const char *value, void *cb)
write_bitmaps = git_config_bool(var, value);
return 0;
}
+ if (!strcmp(var, "repack.usedeltaislands")) {
+ use_delta_islands = git_config_bool(var, value);
+ return 0;
+ }
return git_default_config(var, value, cb);
}
@@ -303,6 +308,8 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
N_("pass --local to git-pack-objects")),
OPT_BOOL('b', "write-bitmap-index", &write_bitmaps,
N_("write bitmap index")),
+ OPT_BOOL('i', "delta-islands", &use_delta_islands,
+ N_("pass --delta-islands to git-pack-objects")),
OPT_STRING(0, "unpack-unreachable", &unpack_unreachable, N_("approxidate"),
N_("with -A, do not loosen objects older than this")),
OPT_BOOL('k', "keep-unreachable", &keep_unreachable,
@@ -363,6 +370,8 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
argv_array_push(&cmd.args, "--exclude-promisor-objects");
if (write_bitmaps)
argv_array_push(&cmd.args, "--write-bitmap-index");
+ if (use_delta_islands)
+ argv_array_push(&cmd.args, "--delta-islands");
if (pack_everything & ALL_INTO_ONE) {
get_non_kept_pack_filenames(&existing_packs, &keep_pack_list);
diff --git a/delta-islands.c b/delta-islands.c
new file mode 100644
index 0000000..8e5018e
--- /dev/null
+++ b/delta-islands.c
@@ -0,0 +1,502 @@
+#include "cache.h"
+#include "attr.h"
+#include "object.h"
+#include "blob.h"
+#include "commit.h"
+#include "tag.h"
+#include "tree.h"
+#include "delta.h"
+#include "pack.h"
+#include "tree-walk.h"
+#include "diff.h"
+#include "revision.h"
+#include "list-objects.h"
+#include "progress.h"
+#include "refs.h"
+#include "khash.h"
+#include "pack-bitmap.h"
+#include "pack-objects.h"
+#include "delta-islands.h"
+#include "sha1-array.h"
+#include "config.h"
+
+KHASH_INIT(str, const char *, void *, 1, kh_str_hash_func, kh_str_hash_equal)
+
+static khash_sha1 *island_marks;
+static unsigned island_counter;
+static unsigned island_counter_core;
+
+static kh_str_t *remote_islands;
+
+struct remote_island {
+ uint64_t hash;
+ struct oid_array oids;
+};
+
+struct island_bitmap {
+ uint32_t refcount;
+ uint32_t bits[FLEX_ARRAY];
+};
+
+static uint32_t island_bitmap_size;
+
+/*
+ * Allocate a new bitmap; if "old" is not NULL, the new bitmap will be a copy
+ * of "old". Otherwise, the new bitmap is empty.
+ */
+static struct island_bitmap *island_bitmap_new(const struct island_bitmap *old)
+{
+ size_t size = sizeof(struct island_bitmap) + (island_bitmap_size * 4);
+ struct island_bitmap *b = xcalloc(1, size);
+
+ if (old)
+ memcpy(b, old, size);
+
+ b->refcount = 1;
+ return b;
+}
+
+static void island_bitmap_or(struct island_bitmap *a, const struct island_bitmap *b)
+{
+ uint32_t i;
+
+ for (i = 0; i < island_bitmap_size; ++i)
+ a->bits[i] |= b->bits[i];
+}
+
+static int island_bitmap_is_subset(struct island_bitmap *self,
+ struct island_bitmap *super)
+{
+ uint32_t i;
+
+ if (self == super)
+ return 1;
+
+ for (i = 0; i < island_bitmap_size; ++i) {
+ if ((self->bits[i] & super->bits[i]) != self->bits[i])
+ return 0;
+ }
+
+ return 1;
+}
+
+#define ISLAND_BITMAP_BLOCK(x) (x / 32)
+#define ISLAND_BITMAP_MASK(x) (1 << (x % 32))
+
+static void island_bitmap_set(struct island_bitmap *self, uint32_t i)
+{
+ self->bits[ISLAND_BITMAP_BLOCK(i)] |= ISLAND_BITMAP_MASK(i);
+}
+
+static int island_bitmap_get(struct island_bitmap *self, uint32_t i)
+{
+ return (self->bits[ISLAND_BITMAP_BLOCK(i)] & ISLAND_BITMAP_MASK(i)) != 0;
+}
+
+int in_same_island(const struct object_id *trg_oid, const struct object_id *src_oid)
+{
+ khiter_t trg_pos, src_pos;
+
+ /* If we aren't using islands, assume everything goes together. */
+ if (!island_marks)
+ return 1;
+
+ /*
+ * If we don't have a bitmap for the target, we can delta it
+ * against anything -- it's not an important object
+ */
+ trg_pos = kh_get_sha1(island_marks, trg_oid->hash);
+ if (trg_pos >= kh_end(island_marks))
+ return 1;
+
+ /*
+ * if the source (our delta base) doesn't have a bitmap,
+ * we don't want to base any deltas on it!
+ */
+ src_pos = kh_get_sha1(island_marks, src_oid->hash);
+ if (src_pos >= kh_end(island_marks))
+ return 0;
+
+ return island_bitmap_is_subset(kh_value(island_marks, trg_pos),
+ kh_value(island_marks, src_pos));
+}
+
+int island_delta_cmp(const struct object_id *a, const struct object_id *b)
+{
+ khiter_t a_pos, b_pos;
+ struct island_bitmap *a_bitmap = NULL, *b_bitmap = NULL;
+
+ if (!island_marks)
+ return 0;
+
+ a_pos = kh_get_sha1(island_marks, a->hash);
+ if (a_pos < kh_end(island_marks))
+ a_bitmap = kh_value(island_marks, a_pos);
+
+ b_pos = kh_get_sha1(island_marks, b->hash);
+ if (b_pos < kh_end(island_marks))
+ b_bitmap = kh_value(island_marks, b_pos);
+
+ if (a_bitmap) {
+ if (!b_bitmap || !island_bitmap_is_subset(a_bitmap, b_bitmap))
+ return -1;
+ }
+ if (b_bitmap) {
+ if (!a_bitmap || !island_bitmap_is_subset(b_bitmap, a_bitmap))
+ return 1;
+ }
+
+ return 0;
+}
+
+static struct island_bitmap *create_or_get_island_marks(struct object *obj)
+{
+ khiter_t pos;
+ int hash_ret;
+
+ pos = kh_put_sha1(island_marks, obj->oid.hash, &hash_ret);
+ if (hash_ret)
+ kh_value(island_marks, pos) = island_bitmap_new(NULL);
+
+ return kh_value(island_marks, pos);
+}
+
+static void set_island_marks(struct object *obj, struct island_bitmap *marks)
+{
+ struct island_bitmap *b;
+ khiter_t pos;
+ int hash_ret;
+
+ pos = kh_put_sha1(island_marks, obj->oid.hash, &hash_ret);
+ if (hash_ret) {
+ /*
+ * We don't have one yet; make a copy-on-write of the
+ * parent.
+ */
+ marks->refcount++;
+ kh_value(island_marks, pos) = marks;
+ return;
+ }
+
+ /*
+ * We do have it. Make sure we split any copy-on-write before
+ * updating.
+ */
+ b = kh_value(island_marks, pos);
+ if (b->refcount > 1) {
+ b->refcount--;
+ b = kh_value(island_marks, pos) = island_bitmap_new(b);
+ }
+ island_bitmap_or(b, marks);
+}
+
+static void mark_remote_island_1(struct remote_island *rl, int is_core_island)
+{
+ uint32_t i;
+
+ for (i = 0; i < rl->oids.nr; ++i) {
+ struct island_bitmap *marks;
+ struct object *obj = parse_object(the_repository, &rl->oids.oid[i]);
+
+ if (!obj)
+ continue;
+
+ marks = create_or_get_island_marks(obj);
+ island_bitmap_set(marks, island_counter);
+
+ if (is_core_island && obj->type == OBJ_COMMIT)
+ obj->flags |= NEEDS_BITMAP;
+
+ /* If it was a tag, also make sure we hit the underlying object. */
+ while (obj && obj->type == OBJ_TAG) {
+ obj = ((struct tag *)obj)->tagged;
+ if (obj) {
+ parse_object(the_repository, &obj->oid);
+ marks = create_or_get_island_marks(obj);
+ island_bitmap_set(marks, island_counter);
+ }
+ }
+ }
+
+ if (is_core_island)
+ island_counter_core = island_counter;
+
+ island_counter++;
+}
+
+struct tree_islands_todo {
+ struct object_entry *entry;
+ unsigned int depth;
+};
+
+static int tree_depth_compare(const void *a, const void *b)
+{
+ const struct tree_islands_todo *todo_a = a;
+ const struct tree_islands_todo *todo_b = b;
+
+ return todo_a->depth - todo_b->depth;
+}
+
+void resolve_tree_islands(int progress, struct packing_data *to_pack)
+{
+ struct progress *progress_state = NULL;
+ struct tree_islands_todo *todo;
+ int nr = 0;
+ int i;
+
+ if (!island_marks)
+ return;
+
+ /*
+ * We process only trees, as commits and tags have already been handled
+ * (and passed their marks on to root trees, as well. We must make sure
+ * to process them in descending tree-depth order so that marks
+ * propagate down the tree properly, even if a sub-tree is found in
+ * multiple parent trees.
+ */
+ ALLOC_ARRAY(todo, to_pack->nr_objects);
+ for (i = 0; i < to_pack->nr_objects; i++) {
+ if (oe_type(&to_pack->objects[i]) == OBJ_TREE) {
+ todo[nr].entry = &to_pack->objects[i];
+ todo[nr].depth = oe_tree_depth(to_pack, &to_pack->objects[i]);
+ nr++;
+ }
+ }
+ QSORT(todo, nr, tree_depth_compare);
+
+ if (progress)
+ progress_state = start_progress(_("Propagating island marks"), nr);
+
+ for (i = 0; i < nr; i++) {
+ struct object_entry *ent = todo[i].entry;
+ struct island_bitmap *root_marks;
+ struct tree *tree;
+ struct tree_desc desc;
+ struct name_entry entry;
+ khiter_t pos;
+
+ pos = kh_get_sha1(island_marks, ent->idx.oid.hash);
+ if (pos >= kh_end(island_marks))
+ continue;
+
+ root_marks = kh_value(island_marks, pos);
+
+ tree = lookup_tree(the_repository, &ent->idx.oid);
+ if (!tree || parse_tree(tree) < 0)
+ die(_("bad tree object %s"), oid_to_hex(&ent->idx.oid));
+
+ init_tree_desc(&desc, tree->buffer, tree->size);
+ while (tree_entry(&desc, &entry)) {
+ struct object *obj;
+
+ if (S_ISGITLINK(entry.mode))
+ continue;
+
+ obj = lookup_object(the_repository, entry.oid->hash);
+ if (!obj)
+ continue;
+
+ set_island_marks(obj, root_marks);
+ }
+
+ free_tree_buffer(tree);
+
+ display_progress(progress_state, i+1);
+ }
+
+ stop_progress(&progress_state);
+ free(todo);
+}
+
+static regex_t *island_regexes;
+static unsigned int island_regexes_alloc, island_regexes_nr;
+static const char *core_island_name;
+
+static int island_config_callback(const char *k, const char *v, void *cb)
+{
+ if (!strcmp(k, "pack.island")) {
+ struct strbuf re = STRBUF_INIT;
+
+ if (!v)
+ return config_error_nonbool(k);
+
+ ALLOC_GROW(island_regexes, island_regexes_nr + 1, island_regexes_alloc);
+
+ if (*v != '^')
+ strbuf_addch(&re, '^');
+ strbuf_addstr(&re, v);
+
+ if (regcomp(&island_regexes[island_regexes_nr], re.buf, REG_EXTENDED))
+ die(_("failed to load island regex for '%s': %s"), k, re.buf);
+
+ strbuf_release(&re);
+ island_regexes_nr++;
+ return 0;
+ }
+
+ if (!strcmp(k, "pack.islandcore"))
+ return git_config_string(&core_island_name, k, v);
+
+ return 0;
+}
+
+static void add_ref_to_island(const char *island_name, const struct object_id *oid)
+{
+ uint64_t sha_core;
+ struct remote_island *rl = NULL;
+
+ int hash_ret;
+ khiter_t pos = kh_put_str(remote_islands, island_name, &hash_ret);
+
+ if (hash_ret) {
+ kh_key(remote_islands, pos) = xstrdup(island_name);
+ kh_value(remote_islands, pos) = xcalloc(1, sizeof(struct remote_island));
+ }
+
+ rl = kh_value(remote_islands, pos);
+ oid_array_append(&rl->oids, oid);
+
+ memcpy(&sha_core, oid->hash, sizeof(uint64_t));
+ rl->hash += sha_core;
+}
+
+static int find_island_for_ref(const char *refname, const struct object_id *oid,
+ int flags, void *data)
+{
+ /*
+ * We should advertise 'ARRAY_SIZE(matches) - 2' as the max,
+ * so we can diagnose below a config with more capture groups
+ * than we support.
+ */
+ regmatch_t matches[16];
+ int i, m;
+ struct strbuf island_name = STRBUF_INIT;
+
+ /* walk backwards to get last-one-wins ordering */
+ for (i = island_regexes_nr - 1; i >= 0; i--) {
+ if (!regexec(&island_regexes[i], refname,
+ ARRAY_SIZE(matches), matches, 0))
+ break;
+ }
+
+ if (i < 0)
+ return 0;
+
+ if (matches[ARRAY_SIZE(matches) - 1].rm_so != -1)
+ warning(_("island regex from config has "
+ "too many capture groups (max=%d)"),
+ (int)ARRAY_SIZE(matches) - 2);
+
+ for (m = 1; m < ARRAY_SIZE(matches); m++) {
+ regmatch_t *match = &matches[m];
+
+ if (match->rm_so == -1)
+ continue;
+
+ if (island_name.len)
+ strbuf_addch(&island_name, '-');
+
+ strbuf_add(&island_name, refname + match->rm_so, match->rm_eo - match->rm_so);
+ }
+
+ add_ref_to_island(island_name.buf, oid);
+ strbuf_release(&island_name);
+ return 0;
+}
+
+static struct remote_island *get_core_island(void)
+{
+ if (core_island_name) {
+ khiter_t pos = kh_get_str(remote_islands, core_island_name);
+ if (pos < kh_end(remote_islands))
+ return kh_value(remote_islands, pos);
+ }
+
+ return NULL;
+}
+
+static void deduplicate_islands(void)
+{
+ struct remote_island *island, *core = NULL, **list;
+ unsigned int island_count, dst, src, ref, i = 0;
+
+ island_count = kh_size(remote_islands);
+ ALLOC_ARRAY(list, island_count);
+
+ kh_foreach_value(remote_islands, island, {
+ list[i++] = island;
+ });
+
+ for (ref = 0; ref + 1 < island_count; ref++) {
+ for (src = ref + 1, dst = src; src < island_count; src++) {
+ if (list[ref]->hash == list[src]->hash)
+ continue;
+
+ if (src != dst)
+ list[dst] = list[src];
+
+ dst++;
+ }
+ island_count = dst;
+ }
+
+ island_bitmap_size = (island_count / 32) + 1;
+ core = get_core_island();
+
+ for (i = 0; i < island_count; ++i) {
+ mark_remote_island_1(list[i], core && list[i]->hash == core->hash);
+ }
+
+ free(list);
+}
+
+void load_delta_islands(void)
+{
+ island_marks = kh_init_sha1();
+ remote_islands = kh_init_str();
+
+ git_config(island_config_callback, NULL);
+ for_each_ref(find_island_for_ref, NULL);
+ deduplicate_islands();
+
+ fprintf(stderr, _("Marked %d islands, done.\n"), island_counter);
+}
+
+void propagate_island_marks(struct commit *commit)
+{
+ khiter_t pos = kh_get_sha1(island_marks, commit->object.oid.hash);
+
+ if (pos < kh_end(island_marks)) {
+ struct commit_list *p;
+ struct island_bitmap *root_marks = kh_value(island_marks, pos);
+
+ parse_commit(commit);
+ set_island_marks(&get_commit_tree(commit)->object, root_marks);
+ for (p = commit->parents; p; p = p->next)
+ set_island_marks(&p->item->object, root_marks);
+ }
+}
+
+int compute_pack_layers(struct packing_data *to_pack)
+{
+ uint32_t i;
+
+ if (!core_island_name || !island_marks)
+ return 1;
+
+ for (i = 0; i < to_pack->nr_objects; ++i) {
+ struct object_entry *entry = &to_pack->objects[i];
+ khiter_t pos = kh_get_sha1(island_marks, entry->idx.oid.hash);
+
+ oe_set_layer(to_pack, entry, 1);
+
+ if (pos < kh_end(island_marks)) {
+ struct island_bitmap *bitmap = kh_value(island_marks, pos);
+
+ if (island_bitmap_get(bitmap, island_counter_core))
+ oe_set_layer(to_pack, entry, 0);
+ }
+ }
+
+ return 2;
+}
diff --git a/delta-islands.h b/delta-islands.h
new file mode 100644
index 0000000..f972573
--- /dev/null
+++ b/delta-islands.h
@@ -0,0 +1,11 @@
+#ifndef DELTA_ISLANDS_H
+#define DELTA_ISLANDS_H
+
+int island_delta_cmp(const struct object_id *a, const struct object_id *b);
+int in_same_island(const struct object_id *, const struct object_id *);
+void resolve_tree_islands(int progress, struct packing_data *to_pack);
+void load_delta_islands(void);
+void propagate_island_marks(struct commit *commit);
+int compute_pack_layers(struct packing_data *to_pack);
+
+#endif /* DELTA_ISLANDS_H */
diff --git a/pack-objects.c b/pack-objects.c
index 3462858..7f7b7dd 100644
--- a/pack-objects.c
+++ b/pack-objects.c
@@ -164,6 +164,12 @@ struct object_entry *packlist_alloc(struct packing_data *pdata,
REALLOC_ARRAY(pdata->in_pack, pdata->nr_alloc);
if (pdata->delta_size)
REALLOC_ARRAY(pdata->delta_size, pdata->nr_alloc);
+
+ if (pdata->tree_depth)
+ REALLOC_ARRAY(pdata->tree_depth, pdata->nr_alloc);
+
+ if (pdata->layer)
+ REALLOC_ARRAY(pdata->layer, pdata->nr_alloc);
}
new_entry = pdata->objects + pdata->nr_objects++;
@@ -179,6 +185,12 @@ struct object_entry *packlist_alloc(struct packing_data *pdata,
if (pdata->in_pack)
pdata->in_pack[pdata->nr_objects - 1] = NULL;
+ if (pdata->tree_depth)
+ pdata->tree_depth[pdata->nr_objects - 1] = 0;
+
+ if (pdata->layer)
+ pdata->layer[pdata->nr_objects - 1] = 0;
+
return new_entry;
}
diff --git a/pack-objects.h b/pack-objects.h
index b0c1f13..2ca39cf 100644
--- a/pack-objects.h
+++ b/pack-objects.h
@@ -103,6 +103,7 @@ struct object_entry {
unsigned no_try_delta:1;
unsigned type_:TYPE_BITS;
unsigned in_pack_type:TYPE_BITS; /* could be delta */
+
unsigned preferred_base:1; /*
* we do not pack this, but is available
* to be used as the base object to delta
@@ -158,6 +159,10 @@ struct packing_data {
uintmax_t oe_size_limit;
uintmax_t oe_delta_size_limit;
+
+ /* delta islands */
+ unsigned int *tree_depth;
+ unsigned char *layer;
};
void prepare_packing_data(struct packing_data *pdata);
@@ -400,4 +405,38 @@ static inline void oe_set_delta_size(struct packing_data *pack,
}
}
+static inline unsigned int oe_tree_depth(struct packing_data *pack,
+ struct object_entry *e)
+{
+ if (!pack->tree_depth)
+ return 0;
+ return pack->tree_depth[e - pack->objects];
+}
+
+static inline void oe_set_tree_depth(struct packing_data *pack,
+ struct object_entry *e,
+ unsigned int tree_depth)
+{
+ if (!pack->tree_depth)
+ ALLOC_ARRAY(pack->tree_depth, pack->nr_objects);
+ pack->tree_depth[e - pack->objects] = tree_depth;
+}
+
+static inline unsigned char oe_layer(struct packing_data *pack,
+ struct object_entry *e)
+{
+ if (!pack->layer)
+ return 0;
+ return pack->layer[e - pack->objects];
+}
+
+static inline void oe_set_layer(struct packing_data *pack,
+ struct object_entry *e,
+ unsigned char layer)
+{
+ if (!pack->layer)
+ ALLOC_ARRAY(pack->layer, pack->nr_objects);
+ pack->layer[e - pack->objects] = layer;
+}
+
#endif
diff --git a/t/t5320-delta-islands.sh b/t/t5320-delta-islands.sh
new file mode 100755
index 0000000..fea92a5
--- /dev/null
+++ b/t/t5320-delta-islands.sh
@@ -0,0 +1,143 @@
+#!/bin/sh
+
+test_description='exercise delta islands'
+. ./test-lib.sh
+
+# returns true iff $1 is a delta based on $2
+is_delta_base () {
+ delta_base=$(echo "$1" | git cat-file --batch-check='%(deltabase)') &&
+ echo >&2 "$1 has base $delta_base" &&
+ test "$delta_base" = "$2"
+}
+
+# generate a commit on branch $1 with a single file, "file", whose
+# content is mostly based on the seed $2, but with a unique bit
+# of content $3 appended. This should allow us to see whether
+# blobs of different refs delta against each other.
+commit() {
+ blob=$({ test-tool genrandom "$2" 10240 && echo "$3"; } |
+ git hash-object -w --stdin) &&
+ tree=$(printf '100644 blob %s\tfile\n' "$blob" | git mktree) &&
+ commit=$(echo "$2-$3" | git commit-tree "$tree" ${4:+-p "$4"}) &&
+ git update-ref "refs/heads/$1" "$commit" &&
+ eval "$1"'=$(git rev-parse $1:file)' &&
+ eval "echo >&2 $1=\$$1"
+}
+
+test_expect_success 'setup commits' '
+ commit one seed 1 &&
+ commit two seed 12
+'
+
+# Note: This is heavily dependent on the "prefer larger objects as base"
+# heuristic.
+test_expect_success 'vanilla repack deltas one against two' '
+ git repack -adf &&
+ is_delta_base $one $two
+'
+
+test_expect_success 'island repack with no island definition is vanilla' '
+ git repack -adfi &&
+ is_delta_base $one $two
+'
+
+test_expect_success 'island repack with no matches is vanilla' '
+ git -c "pack.island=refs/foo" repack -adfi &&
+ is_delta_base $one $two
+'
+
+test_expect_success 'separate islands disallows delta' '
+ git -c "pack.island=refs/heads/(.*)" repack -adfi &&
+ ! is_delta_base $one $two &&
+ ! is_delta_base $two $one
+'
+
+test_expect_success 'same island allows delta' '
+ git -c "pack.island=refs/heads" repack -adfi &&
+ is_delta_base $one $two
+'
+
+test_expect_success 'coalesce same-named islands' '
+ git \
+ -c "pack.island=refs/(.*)/one" \
+ -c "pack.island=refs/(.*)/two" \
+ repack -adfi &&
+ is_delta_base $one $two
+'
+
+test_expect_success 'island restrictions drop reused deltas' '
+ git repack -adfi &&
+ is_delta_base $one $two &&
+ git -c "pack.island=refs/heads/(.*)" repack -adi &&
+ ! is_delta_base $one $two &&
+ ! is_delta_base $two $one
+'
+
+test_expect_success 'island regexes are left-anchored' '
+ git -c "pack.island=heads/(.*)" repack -adfi &&
+ is_delta_base $one $two
+'
+
+test_expect_success 'island regexes follow last-one-wins scheme' '
+ git \
+ -c "pack.island=refs/heads/(.*)" \
+ -c "pack.island=refs/heads/" \
+ repack -adfi &&
+ is_delta_base $one $two
+'
+
+test_expect_success 'setup shared history' '
+ commit root shared root &&
+ commit one shared 1 root &&
+ commit two shared 12-long root
+'
+
+# We know that $two will be preferred as a base from $one,
+# because we can transform it with a pure deletion.
+#
+# We also expect $root as a delta against $two by the "longest is base" rule.
+test_expect_success 'vanilla delta goes between branches' '
+ git repack -adf &&
+ is_delta_base $one $two &&
+ is_delta_base $root $two
+'
+
+# Here we should allow $one to base itself on $root; even though
+# they are in different islands, the objects in $root are in a superset
+# of islands compared to those in $one.
+#
+# Similarly, $two can delta against $root by our rules. And unlike $one,
+# in which we are just allowing it, the island rules actually put $root
+# as a possible base for $two, which it would not otherwise be (due to the size
+# sorting).
+test_expect_success 'deltas allowed against superset islands' '
+ git -c "pack.island=refs/heads/(.*)" repack -adfi &&
+ is_delta_base $one $root &&
+ is_delta_base $two $root
+'
+
+# We are going to test the packfile order here, so we again have to make some
+# assumptions. We assume that "$root", as part of our core "one", must come
+# before "$two". This should be guaranteed by the island code. However, for
+# this test to fail without islands, we are also assuming that it would not
+# otherwise do so. This is true by the current write order, which will put
+# commits (and their contents) before their parents.
+test_expect_success 'island core places core objects first' '
+ cat >expect <<-EOF &&
+ $root
+ $two
+ EOF
+ git -c "pack.island=refs/heads/(.*)" \
+ -c "pack.islandcore=one" \
+ repack -adfi &&
+ git verify-pack -v .git/objects/pack/*.pack |
+ cut -d" " -f1 |
+ egrep "$root|$two" >actual &&
+ test_cmp expect actual
+'
+
+test_expect_success 'unmatched island core is not fatal' '
+ git -c "pack.islandcore=one" repack -adfi
+'
+
+test_done