mirror of
https://github.com/git/git
synced 2024-07-16 10:38:05 +00:00
index-pack: support multithreaded delta resolving
This puts delta resolving on each base on a separate thread, one base cache per thread. Per-thread data is grouped in struct thread_local. When running with nr_threads == 1, no pthreads calls are made. The system essentially runs in non-thread mode. An experiment on a Xeon 24 core machine with git.git shows that performance does not increase proportional to the number of cores. So by default, we use maximum 3 cores. Some numbers with --threads from 1 to 16: 1..4 real 0m8.003s 0m5.307s 0m4.321s 0m3.830s user 0m7.720s 0m8.009s 0m8.133s 0m8.305s sys 0m0.224s 0m0.372s 0m0.360s 0m0.360s 5..8 real 0m3.727s 0m3.604s 0m3.332s 0m3.369s user 0m9.361s 0m9.817s 0m9.525s 0m9.769s sys 0m0.584s 0m0.624s 0m0.540s 0m0.560s 9..12 real 0m3.036s 0m3.139s 0m3.177s 0m2.961s user 0m8.977s 0m10.205s 0m9.737s 0m10.073s sys 0m0.596s 0m0.680s 0m0.684s 0m0.680s 13..16 real 0m2.985s 0m2.894s 0m2.975s 0m2.971s user 0m9.825s 0m10.573s 0m10.833s 0m11.361s sys 0m0.788s 0m0.732s 0m0.904s 0m1.016s On an Intel dual core and linux-2.6.git 1..4 real 2m37.789s 2m7.963s 2m0.920s 1m58.213s user 2m28.415s 2m52.325s 2m50.176s 2m41.187s sys 0m7.808s 0m11.181s 0m11.224s 0m10.731s Thanks Ramsay Jones for troubleshooting and support on MinGW platform. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Nguyễn Thái Ngọc Duy
Junio C Hamano
parent
5272f75587
commit
b8a2486f15
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@ -74,6 +74,16 @@ OPTIONS
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--strict::
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Die, if the pack contains broken objects or links.
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--threads=<n>::
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Specifies the number of threads to spawn when resolving
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deltas. This requires that index-pack be compiled with
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pthreads otherwise this option is ignored with a warning.
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This is meant to reduce packing time on multiprocessor
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machines. The required amount of memory for the delta search
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window is however multiplied by the number of threads.
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Specifying 0 will cause git to auto-detect the number of CPU's
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and use maximum 3 threads.
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Note
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----
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2
Makefile
2
Makefile
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@ -2160,7 +2160,7 @@ builtin/branch.o builtin/checkout.o builtin/clone.o builtin/reset.o branch.o tra
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builtin/bundle.o bundle.o transport.o: bundle.h
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builtin/bisect--helper.o builtin/rev-list.o bisect.o: bisect.h
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builtin/clone.o builtin/fetch-pack.o transport.o: fetch-pack.h
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builtin/grep.o builtin/pack-objects.o transport-helper.o thread-utils.o: thread-utils.h
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builtin/index-pack.o builtin/grep.o builtin/pack-objects.o transport-helper.o thread-utils.o: thread-utils.h
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builtin/send-pack.o transport.o: send-pack.h
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builtin/log.o builtin/shortlog.o: shortlog.h
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builtin/prune.o builtin/reflog.o reachable.o: reachable.h
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@ -9,6 +9,7 @@
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#include "progress.h"
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#include "fsck.h"
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#include "exec_cmd.h"
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#include "thread-utils.h"
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static const char index_pack_usage[] =
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"git index-pack [-v] [-o <index-file>] [--keep | --keep=<msg>] [--verify] [--strict] (<pack-file> | --stdin [--fix-thin] [<pack-file>])";
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@ -38,6 +39,14 @@ struct base_data {
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int ofs_first, ofs_last;
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};
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struct thread_local {
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#ifndef NO_PTHREADS
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pthread_t thread;
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#endif
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struct base_data *base_cache;
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size_t base_cache_used;
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};
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/*
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* Even if sizeof(union delta_base) == 24 on 64-bit archs, we really want
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* to memcmp() only the first 20 bytes.
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@ -54,11 +63,11 @@ struct delta_entry {
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static struct object_entry *objects;
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static struct delta_entry *deltas;
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static struct base_data *base_cache;
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static size_t base_cache_used;
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static struct thread_local nothread_data;
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static int nr_objects;
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static int nr_deltas;
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static int nr_resolved_deltas;
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static int nr_threads;
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static int from_stdin;
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static int strict;
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@ -75,6 +84,77 @@ static git_SHA_CTX input_ctx;
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static uint32_t input_crc32;
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static int input_fd, output_fd, pack_fd;
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#ifndef NO_PTHREADS
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static struct thread_local *thread_data;
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static int nr_dispatched;
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static int threads_active;
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static pthread_mutex_t read_mutex;
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#define read_lock() lock_mutex(&read_mutex)
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#define read_unlock() unlock_mutex(&read_mutex)
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static pthread_mutex_t counter_mutex;
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#define counter_lock() lock_mutex(&counter_mutex)
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#define counter_unlock() unlock_mutex(&counter_mutex)
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static pthread_mutex_t work_mutex;
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#define work_lock() lock_mutex(&work_mutex)
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#define work_unlock() unlock_mutex(&work_mutex)
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static pthread_key_t key;
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static inline void lock_mutex(pthread_mutex_t *mutex)
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{
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if (threads_active)
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pthread_mutex_lock(mutex);
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}
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static inline void unlock_mutex(pthread_mutex_t *mutex)
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{
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if (threads_active)
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pthread_mutex_unlock(mutex);
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}
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/*
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* Mutex and conditional variable can't be statically-initialized on Windows.
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*/
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static void init_thread(void)
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{
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init_recursive_mutex(&read_mutex);
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pthread_mutex_init(&counter_mutex, NULL);
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pthread_mutex_init(&work_mutex, NULL);
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pthread_key_create(&key, NULL);
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thread_data = xcalloc(nr_threads, sizeof(*thread_data));
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threads_active = 1;
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}
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static void cleanup_thread(void)
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{
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if (!threads_active)
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return;
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threads_active = 0;
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pthread_mutex_destroy(&read_mutex);
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pthread_mutex_destroy(&counter_mutex);
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pthread_mutex_destroy(&work_mutex);
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pthread_key_delete(key);
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free(thread_data);
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}
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#else
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#define read_lock()
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#define read_unlock()
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#define counter_lock()
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#define counter_unlock()
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#define work_lock()
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#define work_unlock()
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#endif
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static int mark_link(struct object *obj, int type, void *data)
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{
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if (!obj)
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@ -223,6 +303,25 @@ static NORETURN void bad_object(unsigned long offset, const char *format, ...)
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die("pack has bad object at offset %lu: %s", offset, buf);
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}
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static inline struct thread_local *get_thread_data(void)
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{
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#ifndef NO_PTHREADS
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if (threads_active)
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return pthread_getspecific(key);
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assert(!threads_active &&
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"This should only be reached when all threads are gone");
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#endif
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return ¬hread_data;
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}
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#ifndef NO_PTHREADS
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static void set_thread_data(struct thread_local *data)
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{
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if (threads_active)
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pthread_setspecific(key, data);
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}
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#endif
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static struct base_data *alloc_base_data(void)
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{
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struct base_data *base = xmalloc(sizeof(struct base_data));
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@ -237,15 +336,16 @@ static void free_base_data(struct base_data *c)
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if (c->data) {
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free(c->data);
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c->data = NULL;
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base_cache_used -= c->size;
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get_thread_data()->base_cache_used -= c->size;
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}
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}
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static void prune_base_data(struct base_data *retain)
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{
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struct base_data *b;
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for (b = base_cache;
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base_cache_used > delta_base_cache_limit && b;
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struct thread_local *data = get_thread_data();
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for (b = data->base_cache;
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data->base_cache_used > delta_base_cache_limit && b;
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b = b->child) {
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if (b->data && b != retain)
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free_base_data(b);
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@ -257,12 +357,12 @@ static void link_base_data(struct base_data *base, struct base_data *c)
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if (base)
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base->child = c;
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else
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base_cache = c;
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get_thread_data()->base_cache = c;
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c->base = base;
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c->child = NULL;
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if (c->data)
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base_cache_used += c->size;
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get_thread_data()->base_cache_used += c->size;
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prune_base_data(c);
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}
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@ -272,7 +372,7 @@ static void unlink_base_data(struct base_data *c)
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if (base)
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base->child = NULL;
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else
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base_cache = NULL;
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get_thread_data()->base_cache = NULL;
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free_base_data(c);
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}
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@ -461,19 +561,24 @@ static void sha1_object(const void *data, unsigned long size,
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enum object_type type, unsigned char *sha1)
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{
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hash_sha1_file(data, size, typename(type), sha1);
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read_lock();
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if (has_sha1_file(sha1)) {
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void *has_data;
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enum object_type has_type;
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unsigned long has_size;
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has_data = read_sha1_file(sha1, &has_type, &has_size);
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read_unlock();
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if (!has_data)
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die("cannot read existing object %s", sha1_to_hex(sha1));
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if (size != has_size || type != has_type ||
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memcmp(data, has_data, size) != 0)
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die("SHA1 COLLISION FOUND WITH %s !", sha1_to_hex(sha1));
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free(has_data);
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}
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} else
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read_unlock();
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if (strict) {
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read_lock();
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if (type == OBJ_BLOB) {
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struct blob *blob = lookup_blob(sha1);
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if (blob)
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@ -507,6 +612,7 @@ static void sha1_object(const void *data, unsigned long size,
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}
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obj->flags |= FLAG_CHECKED;
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}
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read_unlock();
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}
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}
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@ -552,7 +658,7 @@ static void *get_base_data(struct base_data *c)
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if (!delta_nr) {
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c->data = get_data_from_pack(obj);
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c->size = obj->size;
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base_cache_used += c->size;
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get_thread_data()->base_cache_used += c->size;
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prune_base_data(c);
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}
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for (; delta_nr > 0; delta_nr--) {
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@ -568,7 +674,7 @@ static void *get_base_data(struct base_data *c)
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free(raw);
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if (!c->data)
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bad_object(obj->idx.offset, "failed to apply delta");
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base_cache_used += c->size;
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get_thread_data()->base_cache_used += c->size;
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prune_base_data(c);
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}
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free(delta);
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@ -596,7 +702,9 @@ static void resolve_delta(struct object_entry *delta_obj,
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bad_object(delta_obj->idx.offset, "failed to apply delta");
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sha1_object(result->data, result->size, delta_obj->real_type,
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delta_obj->idx.sha1);
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counter_lock();
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nr_resolved_deltas++;
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counter_unlock();
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}
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static struct base_data *find_unresolved_deltas_1(struct base_data *base,
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@ -690,6 +798,30 @@ static void resolve_base(struct object_entry *obj)
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find_unresolved_deltas(base_obj);
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}
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#ifndef NO_PTHREADS
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static void *threaded_second_pass(void *data)
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{
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set_thread_data(data);
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for (;;) {
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int i;
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work_lock();
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display_progress(progress, nr_resolved_deltas);
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while (nr_dispatched < nr_objects &&
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is_delta_type(objects[nr_dispatched].type))
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nr_dispatched++;
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if (nr_dispatched >= nr_objects) {
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work_unlock();
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break;
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}
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i = nr_dispatched++;
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work_unlock();
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resolve_base(&objects[i]);
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}
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return NULL;
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}
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#endif
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/*
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* First pass:
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* - find locations of all objects;
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@ -758,6 +890,24 @@ static void resolve_deltas(void)
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if (verbose)
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progress = start_progress("Resolving deltas", nr_deltas);
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#ifndef NO_PTHREADS
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nr_dispatched = 0;
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if (nr_threads > 1 || getenv("GIT_FORCE_THREADS")) {
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init_thread();
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for (i = 0; i < nr_threads; i++) {
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int ret = pthread_create(&thread_data[i].thread, NULL,
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threaded_second_pass, thread_data + i);
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if (ret)
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die("unable to create thread: %s", strerror(ret));
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}
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for (i = 0; i < nr_threads; i++)
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pthread_join(thread_data[i].thread, NULL);
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cleanup_thread();
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return;
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}
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#endif
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for (i = 0; i < nr_objects; i++) {
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struct object_entry *obj = &objects[i];
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@ -1016,6 +1166,18 @@ static int git_index_pack_config(const char *k, const char *v, void *cb)
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die("bad pack.indexversion=%"PRIu32, opts->version);
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return 0;
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}
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if (!strcmp(k, "pack.threads")) {
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nr_threads = git_config_int(k, v);
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if (nr_threads < 0)
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die("invalid number of threads specified (%d)",
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nr_threads);
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#ifdef NO_PTHREADS
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if (nr_threads != 1)
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warning("no threads support, ignoring %s", k);
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nr_threads = 1;
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#endif
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return 0;
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}
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return git_default_config(k, v, cb);
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}
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@ -1174,6 +1336,17 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
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keep_msg = "";
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} else if (!prefixcmp(arg, "--keep=")) {
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keep_msg = arg + 7;
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} else if (!prefixcmp(arg, "--threads=")) {
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char *end;
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nr_threads = strtoul(arg+10, &end, 0);
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if (!arg[10] || *end || nr_threads < 0)
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usage(index_pack_usage);
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#ifdef NO_PTHREADS
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if (nr_threads != 1)
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warning("no threads support, "
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"ignoring %s", arg);
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nr_threads = 1;
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#endif
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} else if (!prefixcmp(arg, "--pack_header=")) {
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struct pack_header *hdr;
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char *c;
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@ -1245,6 +1418,15 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
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if (strict)
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opts.flags |= WRITE_IDX_STRICT;
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#ifndef NO_PTHREADS
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if (!nr_threads) {
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nr_threads = online_cpus();
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/* An experiment showed that more threads does not mean faster */
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if (nr_threads > 3)
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nr_threads = 3;
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}
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#endif
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curr_pack = open_pack_file(pack_name);
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parse_pack_header();
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objects = xcalloc(nr_objects + 1, sizeof(struct object_entry));
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40
t/perf/p5302-pack-index.sh
Executable file
40
t/perf/p5302-pack-index.sh
Executable file
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@ -0,0 +1,40 @@
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#!/bin/sh
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test_description="Tests index-pack performance"
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. ./perf-lib.sh
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test_perf_large_repo
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test_expect_success 'repack' '
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git repack -ad &&
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PACK=`ls .git/objects/pack/*.pack | head -n1` &&
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test -f "$PACK" &&
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export PACK
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'
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test_perf 'index-pack 0 threads' '
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GIT_DIR=t1 git index-pack --threads=1 --stdin < $PACK
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'
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test_perf 'index-pack 1 thread ' '
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GIT_DIR=t2 GIT_FORCE_THREADS=1 git index-pack --threads=1 --stdin < $PACK
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'
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test_perf 'index-pack 2 threads' '
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GIT_DIR=t3 git index-pack --threads=2 --stdin < $PACK
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'
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test_perf 'index-pack 4 threads' '
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GIT_DIR=t4 git index-pack --threads=4 --stdin < $PACK
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'
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test_perf 'index-pack 8 threads' '
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GIT_DIR=t5 git index-pack --threads=8 --stdin < $PACK
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'
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test_perf 'index-pack default number of threads' '
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GIT_DIR=t6 git index-pack --stdin < $PACK
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'
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test_done
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