mirrors/git
0
0
Fork 0
mirror of https://github.com/git/git.git synced 2024-12-14 12:23:35 +08:00
Code Issues Packages Projects Releases Wiki Activity

Merge branch 'jt/threaded-index-pack'

Browse Source 
"git index-pack" learned to resolve deltified objects with greater
parallelism.

* jt/threaded-index-pack:
  index-pack: make quantum of work smaller
  index-pack: make resolve_delta() assume base data
  index-pack: calculate {ref,ofs}_{first,last} early
  index-pack: remove redundant child field
  index-pack: unify threaded and unthreaded code
  index-pack: remove redundant parameter
  Documentation: deltaBaseCacheLimit is per-thread
This commit is contained in:
Junio C Hamano 2020-09-22 12:36:28 -07:00
commit b7e65b51e5
2 changed files with 251 additions and 207 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/config/core.txt
View File

@ -399,7 +399,7 @@ the largest projects. You probably do not need to adjust this value.
Common unit suffixes of 'k', 'm', or 'g' are supported.
core.deltaBaseCacheLimit::
Maximum number of bytes to reserve for caching base objects
Maximum number of bytes per thread to reserve for caching base objects
that may be referenced by multiple deltified objects. By storing the
entire decompressed base objects in a cache Git is able
to avoid unpacking and decompressing frequently used base

456
builtin/index-pack.c
View File

@ -33,19 +33,61 @@ struct object_stat {
};
struct base_data {
/* Initialized by make_base(). */
struct base_data *base;
struct base_data *child;
struct object_entry *obj;
void *data;
unsigned long size;
int ref_first, ref_last;
int ofs_first, ofs_last;
/*
* Threads should increment retain_data if they are about to call
* patch_delta() using this struct's data as a base, and decrement this
* when they are done. While retain_data is nonzero, this struct's data
* will not be freed even if the delta base cache limit is exceeded.
*/
int retain_data;
/*
* The number of direct children that have not been fully processed
* (entered work_head, entered done_head, left done_head). When this
* number reaches zero, this struct base_data can be freed.
*/
int children_remaining;
/* Not initialized by make_base(). */
struct list_head list;
void *data;
unsigned long size;
};
/*
* Stack of struct base_data that have unprocessed children.
* threaded_second_pass() uses this as a source of work (the other being the
* objects array).
*
* Guarded by work_mutex.
*/
static LIST_HEAD(work_head);
/*
* Stack of struct base_data that have children, all of whom have been
* processed or are being processed, and at least one child is being processed.
* These struct base_data must be kept around until the last child is
* processed.
*
* Guarded by work_mutex.
*/
static LIST_HEAD(done_head);
/*
* All threads share one delta base cache.
*
* base_cache_used is guarded by work_mutex, and base_cache_limit is read-only
* in a thread.
*/
static size_t base_cache_used;
static size_t base_cache_limit;
struct thread_local {
pthread_t thread;
struct base_data *base_cache;
size_t base_cache_used;
int pack_fd;
};
@ -364,56 +406,42 @@ static void set_thread_data(struct thread_local *data)
pthread_setspecific(key, data);
}
static struct base_data *alloc_base_data(void)
{
struct base_data *base = xcalloc(1, sizeof(struct base_data));
base->ref_last = -1;
base->ofs_last = -1;
return base;
}
static void free_base_data(struct base_data *c)
{
if (c->data) {
FREE_AND_NULL(c->data);
get_thread_data()->base_cache_used -= c->size;
base_cache_used -= c->size;
}
}
static void prune_base_data(struct base_data *retain)
{
struct base_data *b;
struct thread_local *data = get_thread_data();
for (b = data->base_cache;
data->base_cache_used > delta_base_cache_limit && b;
b = b->child) {
if (b->data && b != retain)
struct list_head *pos;
if (base_cache_used <= base_cache_limit)
return;
list_for_each_prev(pos, &done_head) {
struct base_data *b = list_entry(pos, struct base_data, list);
if (b->retain_data || b == retain)
continue;
if (b->data) {
free_base_data(b);
if (base_cache_used <= base_cache_limit)
return;
}
}
}
static void link_base_data(struct base_data *base, struct base_data *c)
{
if (base)
base->child = c;
else
get_thread_data()->base_cache = c;
c->base = base;
c->child = NULL;
if (c->data)
get_thread_data()->base_cache_used += c->size;
prune_base_data(c);
}
static void unlink_base_data(struct base_data *c)
{
struct base_data *base = c->base;
if (base)
base->child = NULL;
else
get_thread_data()->base_cache = NULL;
free_base_data(c);
list_for_each_prev(pos, &work_head) {
struct base_data *b = list_entry(pos, struct base_data, list);
if (b->retain_data || b == retain)
continue;
if (b->data) {
free_base_data(b);
if (base_cache_used <= base_cache_limit)
return;
}
}
}
static int is_delta_type(enum object_type type)
@ -614,7 +642,7 @@ static int compare_ofs_delta_bases(off_t offset1, off_t offset2,
0;
}
static int find_ofs_delta(const off_t offset, enum object_type type)
static int find_ofs_delta(const off_t offset)
{
int first = 0, last = nr_ofs_deltas;
@ -624,7 +652,8 @@ static int find_ofs_delta(const off_t offset, enum object_type type)
int cmp;
cmp = compare_ofs_delta_bases(offset, delta->offset,
type, objects[delta->obj_no].type);
OBJ_OFS_DELTA,
objects[delta->obj_no].type);
if (!cmp)
return next;
if (cmp < 0) {
@ -637,10 +666,9 @@ static int find_ofs_delta(const off_t offset, enum object_type type)
}
static void find_ofs_delta_children(off_t offset,
int *first_index, int *last_index,
enum object_type type)
int *first_index, int *last_index)
{
int first = find_ofs_delta(offset, type);
int first = find_ofs_delta(offset);
int last = first;
int end = nr_ofs_deltas - 1;
@ -668,7 +696,7 @@ static int compare_ref_delta_bases(const struct object_id *oid1,
return oidcmp(oid1, oid2);
}
static int find_ref_delta(const struct object_id *oid, enum object_type type)
static int find_ref_delta(const struct object_id *oid)
{
int first = 0, last = nr_ref_deltas;
@ -678,7 +706,8 @@ static int find_ref_delta(const struct object_id *oid, enum object_type type)
int cmp;
cmp = compare_ref_delta_bases(oid, &delta->oid,
type, objects[delta->obj_no].type);
OBJ_REF_DELTA,
objects[delta->obj_no].type);
if (!cmp)
return next;
if (cmp < 0) {
@ -691,10 +720,9 @@ static int find_ref_delta(const struct object_id *oid, enum object_type type)
}
static void find_ref_delta_children(const struct object_id *oid,
int *first_index, int *last_index,
enum object_type type)
int *first_index, int *last_index)
{
int first = find_ref_delta(oid, type);
int first = find_ref_delta(oid);
int last = first;
int end = nr_ref_deltas - 1;
@ -866,15 +894,7 @@ static void sha1_object(const void *data, struct object_entry *obj_entry,
}
/*
* This function is part of find_unresolved_deltas(). There are two
* walkers going in the opposite ways.
*
* The first one in find_unresolved_deltas() traverses down from
* parent node to children, deflating nodes along the way. However,
* memory for deflated nodes is limited by delta_base_cache_limit, so
* at some point parent node's deflated content may be freed.
*
* The second walker is this function, which goes from current node up
* Walk from current node up
* to top parent if necessary to deflate the node. In normal
* situation, its parent node would be already deflated, so it just
* needs to apply delta.
@ -902,7 +922,7 @@ static void *get_base_data(struct base_data *c)
if (!delta_nr) {
c->data = get_data_from_pack(obj);
c->size = obj->size;
get_thread_data()->base_cache_used += c->size;
base_cache_used += c->size;
prune_base_data(c);
}
for (; delta_nr > 0; delta_nr--) {
@ -918,7 +938,7 @@ static void *get_base_data(struct base_data *c)
free(raw);
if (!c->data)
bad_object(obj->idx.offset, _("failed to apply delta"));
get_thread_data()->base_cache_used += c->size;
base_cache_used += c->size;
prune_base_data(c);
}
free(delta);
@ -926,10 +946,27 @@ static void *get_base_data(struct base_data *c)
return c->data;
}
static void resolve_delta(struct object_entry *delta_obj,
struct base_data *base, struct base_data *result)
static struct base_data *make_base(struct object_entry *obj,
struct base_data *parent)
{
void *base_data, *delta_data;
struct base_data *base = xcalloc(1, sizeof(struct base_data));
base->base = parent;
base->obj = obj;
find_ref_delta_children(&obj->idx.oid,
&base->ref_first, &base->ref_last);
find_ofs_delta_children(obj->idx.offset,
&base->ofs_first, &base->ofs_last);
base->children_remaining = base->ref_last - base->ref_first +
base->ofs_last - base->ofs_first + 2;
return base;
}
static struct base_data *resolve_delta(struct object_entry *delta_obj,
struct base_data *base)
{
void *delta_data, *result_data;
struct base_data *result;
unsigned long result_size;
if (show_stat) {
int i = delta_obj - objects;
@ -942,115 +979,26 @@ static void resolve_delta(struct object_entry *delta_obj,
obj_stat[i].base_object_no = j;
}
delta_data = get_data_from_pack(delta_obj);
base_data = get_base_data(base);
result->obj = delta_obj;
result->data = patch_delta(base_data, base->size,
delta_data, delta_obj->size, &result->size);
assert(base->data);
result_data = patch_delta(base->data, base->size,
delta_data, delta_obj->size, &result_size);
free(delta_data);
if (!result->data)
if (!result_data)
bad_object(delta_obj->idx.offset, _("failed to apply delta"));
hash_object_file(the_hash_algo, result->data, result->size,
hash_object_file(the_hash_algo, result_data, result_size,
type_name(delta_obj->real_type), &delta_obj->idx.oid);
sha1_object(result->data, NULL, result->size, delta_obj->real_type,
sha1_object(result_data, NULL, result_size, delta_obj->real_type,
&delta_obj->idx.oid);
result = make_base(delta_obj, base);
result->data = result_data;
result->size = result_size;
counter_lock();
nr_resolved_deltas++;
counter_unlock();
}
/*
* Standard boolean compare-and-swap: atomically check whether "*type" is
* "want"; if so, swap in "set" and return true. Otherwise, leave it untouched
* and return false.
*/
static int compare_and_swap_type(signed char *type,
enum object_type want,
enum object_type set)
{
enum object_type old;
type_cas_lock();
old = *type;
if (old == want)
*type = set;
type_cas_unlock();
return old == want;
}
static struct base_data *find_unresolved_deltas_1(struct base_data *base,
struct base_data *prev_base)
{
if (base->ref_last == -1 && base->ofs_last == -1) {
find_ref_delta_children(&base->obj->idx.oid,
&base->ref_first, &base->ref_last,
OBJ_REF_DELTA);
find_ofs_delta_children(base->obj->idx.offset,
&base->ofs_first, &base->ofs_last,
OBJ_OFS_DELTA);
if (base->ref_last == -1 && base->ofs_last == -1) {
free(base->data);
return NULL;
}
link_base_data(prev_base, base);
}
if (base->ref_first <= base->ref_last) {
struct object_entry *child = objects + ref_deltas[base->ref_first].obj_no;
struct base_data *result = alloc_base_data();
if (!compare_and_swap_type(&child->real_type, OBJ_REF_DELTA,
base->obj->real_type))
die("REF_DELTA at offset %"PRIuMAX" already resolved (duplicate base %s?)",
(uintmax_t)child->idx.offset,
oid_to_hex(&base->obj->idx.oid));
resolve_delta(child, base, result);
if (base->ref_first == base->ref_last && base->ofs_last == -1)
free_base_data(base);
base->ref_first++;
return result;
}
if (base->ofs_first <= base->ofs_last) {
struct object_entry *child = objects + ofs_deltas[base->ofs_first].obj_no;
struct base_data *result = alloc_base_data();
assert(child->real_type == OBJ_OFS_DELTA);
child->real_type = base->obj->real_type;
resolve_delta(child, base, result);
if (base->ofs_first == base->ofs_last)
free_base_data(base);
base->ofs_first++;
return result;
}
unlink_base_data(base);
return NULL;
}
static void find_unresolved_deltas(struct base_data *base)
{
struct base_data *new_base, *prev_base = NULL;
for (;;) {
new_base = find_unresolved_deltas_1(base, prev_base);
if (new_base) {
prev_base = base;
base = new_base;
} else {
free(base);
base = prev_base;
if (!base)
return;
prev_base = base->base;
}
}
return result;
}
static int compare_ofs_delta_entry(const void *a, const void *b)
@ -1071,34 +1019,131 @@ static int compare_ref_delta_entry(const void *a, const void *b)
return oidcmp(&delta_a->oid, &delta_b->oid);
}
static void resolve_base(struct object_entry *obj)
{
struct base_data *base_obj = alloc_base_data();
base_obj->obj = obj;
base_obj->data = NULL;
find_unresolved_deltas(base_obj);
}
static void *threaded_second_pass(void *data)
{
set_thread_data(data);
if (data)
set_thread_data(data);
for (;;) {
int i;
counter_lock();
display_progress(progress, nr_resolved_deltas);
counter_unlock();
struct base_data *parent = NULL;
struct object_entry *child_obj;
struct base_data *child;
work_lock();
while (nr_dispatched < nr_objects &&
is_delta_type(objects[nr_dispatched].type))
nr_dispatched++;
if (nr_dispatched >= nr_objects) {
work_unlock();
break;
if (list_empty(&work_head)) {
/*
* Take an object from the object array.
*/
while (nr_dispatched < nr_objects &&
is_delta_type(objects[nr_dispatched].type))
nr_dispatched++;
if (nr_dispatched >= nr_objects) {
work_unlock();
break;
}
child_obj = &objects[nr_dispatched++];
} else {
/*
* Peek at the top of the stack, and take a child from
* it.
*/
parent = list_first_entry(&work_head, struct base_data,
list);
if (parent->ref_first <= parent->ref_last) {
int offset = ref_deltas[parent->ref_first++].obj_no;
child_obj = objects + offset;
if (child_obj->real_type != OBJ_REF_DELTA)
die("REF_DELTA at offset %"PRIuMAX" already resolved (duplicate base %s?)",
(uintmax_t) child_obj->idx.offset,
oid_to_hex(&parent->obj->idx.oid));
child_obj->real_type = parent->obj->real_type;
} else {
child_obj = objects +
ofs_deltas[parent->ofs_first++].obj_no;
assert(child_obj->real_type == OBJ_OFS_DELTA);
child_obj->real_type = parent->obj->real_type;
}
if (parent->ref_first > parent->ref_last &&
parent->ofs_first > parent->ofs_last) {
/*
* This parent has run out of children, so move
* it to done_head.
*/
list_del(&parent->list);
list_add(&parent->list, &done_head);
}
/*
* Ensure that the parent has data, since we will need
* it later.
*
* NEEDSWORK: If parent data needs to be reloaded, this
* prolongs the time that the current thread spends in
* the mutex. A mitigating factor is that parent data
* needs to be reloaded only if the delta base cache
* limit is exceeded, so in the typical case, this does
* not happen.
*/
get_base_data(parent);
parent->retain_data++;
}
i = nr_dispatched++;
work_unlock();
resolve_base(&objects[i]);
if (parent) {
child = resolve_delta(child_obj, parent);
if (!child->children_remaining)
FREE_AND_NULL(child->data);
} else {
child = make_base(child_obj, NULL);
if (child->children_remaining) {
/*
* Since this child has its own delta children,
* we will need this data in the future.
* Inflate now so that future iterations will
* have access to this object's data while
* outside the work mutex.
*/
child->data = get_data_from_pack(child_obj);
child->size = child_obj->size;
}
}
work_lock();
if (parent)
parent->retain_data--;
if (child->data) {
/*
* This child has its own children, so add it to
* work_head.
*/
list_add(&child->list, &work_head);
base_cache_used += child->size;
prune_base_data(NULL);
} else {
/*
* This child does not have its own children. It may be
* the last descendant of its ancestors; free those
* that we can.
*/
struct base_data *p = parent;
while (p) {
struct base_data *next_p;
p->children_remaining--;
if (p->children_remaining)
break;
next_p = p->base;
free_base_data(p);
list_del(&p->list);
free(p);
p = next_p;
}
}
work_unlock();
}
return NULL;
}
@ -1199,6 +1244,7 @@ static void resolve_deltas(void)
nr_ref_deltas + nr_ofs_deltas);
nr_dispatched = 0;
base_cache_limit = delta_base_cache_limit * nr_threads;
if (nr_threads > 1 || getenv("GIT_FORCE_THREADS")) {
init_thread();
for (i = 0; i < nr_threads; i++) {
@ -1213,15 +1259,7 @@ static void resolve_deltas(void)
cleanup_thread();
return;
}
for (i = 0; i < nr_objects; i++) {
struct object_entry *obj = &objects[i];
if (is_delta_type(obj->type))
continue;
resolve_base(obj);
display_progress(progress, nr_resolved_deltas);
}
threaded_second_pass(&nothread_data);
}
/*
@ -1376,22 +1414,28 @@ static void fix_unresolved_deltas(struct hashfile *f)
for (i = 0; i < nr_ref_deltas; i++) {
struct ref_delta_entry *d = sorted_by_pos[i];
enum object_type type;
struct base_data *base_obj = alloc_base_data();
void *data;
unsigned long size;
if (objects[d->obj_no].real_type != OBJ_REF_DELTA)
continue;
base_obj->data = read_object_file(&d->oid, &type,
&base_obj->size);
if (!base_obj->data)
data = read_object_file(&d->oid, &type, &size);
if (!data)
continue;
if (check_object_signature(the_repository, &d->oid,
base_obj->data, base_obj->size,
data, size,
type_name(type)))
die(_("local object %s is corrupt"), oid_to_hex(&d->oid));
base_obj->obj = append_obj_to_pack(f, d->oid.hash,
base_obj->data, base_obj->size, type);
find_unresolved_deltas(base_obj);
/*
* Add this as an object to the objects array and call
* threaded_second_pass() (which will pick up the added
* object).
*/
append_obj_to_pack(f, d->oid.hash, data, size, type);
threaded_second_pass(NULL);
display_progress(progress, nr_resolved_deltas);
}
free(sorted_by_pos);