1 files changed, 489 insertions, 8 deletions

diff --git a/name-hash.c b/name-hash.c
index 6d9f23e932..39309efb7f 100644
--- a/name-hash.c
+++ b/name-hash.c
@@ -23,15 +23,21 @@ static int dir_entry_cmp(const struct dir_entry *e1,
 			name ? name : e2->name, e1->namelen);
 }
 
-static struct dir_entry *find_dir_entry(struct index_state *istate,
-		const char *name, unsigned int namelen)
+static struct dir_entry *find_dir_entry__hash(struct index_state *istate,
+		const char *name, unsigned int namelen, unsigned int hash)
 {
 	struct dir_entry key;
-	hashmap_entry_init(&key, memihash(name, namelen));
+	hashmap_entry_init(&key, hash);
 	key.namelen = namelen;
 	return hashmap_get(&istate->dir_hash, &key, name);
 }
 
+static struct dir_entry *find_dir_entry(struct index_state *istate,
+		const char *name, unsigned int namelen)
+{
+	return find_dir_entry__hash(istate, name, namelen, memihash(name, namelen));
+}
+
 static struct dir_entry *hash_dir_entry(struct index_state *istate,
 		struct cache_entry *ce, int namelen)
 {
@@ -112,20 +118,495 @@ static int cache_entry_cmp(const struct cache_entry *ce1,
 	return remove ? !(ce1 == ce2) : 0;
 }
 
-static void lazy_init_name_hash(struct index_state *istate)
+static int lazy_try_threaded = 1;
+static int lazy_nr_dir_threads;
+
+#ifdef NO_PTHREADS
+
+static inline int lookup_lazy_params(struct index_state *istate)
 {
-	int nr;
+	return 0;
+}
+
+static inline void threaded_lazy_init_name_hash(
+	struct index_state *istate)
+{
+}
+
+#else
+
+#include "thread-utils.h"
+
+/*
+ * Set a minimum number of cache_entries that we will handle per
+ * thread and use that to decide how many threads to run (upto
+ * the number on the system).
+ *
+ * For guidance setting the lower per-thread bound, see:
+ *     t/helper/test-lazy-init-name-hash --analyze
+ */
+#define LAZY_THREAD_COST (2000)
+
+/*
+ * We use n mutexes to guard n partitions of the "istate->dir_hash"
+ * hashtable.  Since "find" and "insert" operations will hash to a
+ * particular bucket and modify/search a single chain, we can say
+ * that "all chains mod n" are guarded by the same mutex -- rather
+ * than having a single mutex to guard the entire table.  (This does
+ * require that we disable "rehashing" on the hashtable.)
+ *
+ * So, a larger value here decreases the probability of a collision
+ * and the time that each thread must wait for the mutex.
+ */
+#define LAZY_MAX_MUTEX   (32)
+
+static pthread_mutex_t *lazy_dir_mutex_array;
+
+/*
+ * An array of lazy_entry items is used by the n threads in
+ * the directory parse (first) phase to (lock-free) store the
+ * intermediate results.  These values are then referenced by
+ * the 2 threads in the second phase.
+ */
+struct lazy_entry {
+	struct dir_entry *dir;
+	unsigned int hash_dir;
+	unsigned int hash_name;
+};
+
+/*
+ * Decide if we want to use threads (if available) to load
+ * the hash tables.  We set "lazy_nr_dir_threads" to zero when
+ * it is not worth it.
+ */
+static int lookup_lazy_params(struct index_state *istate)
+{
+	int nr_cpus;
+
+	lazy_nr_dir_threads = 0;
+
+	if (!lazy_try_threaded)
+		return 0;
+
+	/*
+	 * If we are respecting case, just use the original
+	 * code to build the "istate->name_hash".  We don't
+	 * need the complexity here.
+	 */
+	if (!ignore_case)
+		return 0;
+
+	nr_cpus = online_cpus();
+	if (nr_cpus < 2)
+		return 0;
+
+	if (istate->cache_nr < 2 * LAZY_THREAD_COST)
+		return 0;
+
+	if (istate->cache_nr < nr_cpus * LAZY_THREAD_COST)
+		nr_cpus = istate->cache_nr / LAZY_THREAD_COST;
+	lazy_nr_dir_threads = nr_cpus;
+	return lazy_nr_dir_threads;
+}
+
+/*
+ * Initialize n mutexes for use when searching and inserting
+ * into "istate->dir_hash".  All "dir" threads are trying
+ * to insert partial pathnames into the hash as they iterate
+ * over their portions of the index, so lock contention is
+ * high.
+ *
+ * However, the hashmap is going to put items into bucket
+ * chains based on their hash values.  Use that to create n
+ * mutexes and lock on mutex[bucket(hash) % n].  This will
+ * decrease the collision rate by (hopefully) by a factor of n.
+ */
+static void init_dir_mutex(void)
+{
+	int j;
+
+	lazy_dir_mutex_array = xcalloc(LAZY_MAX_MUTEX, sizeof(pthread_mutex_t));
+
+	for (j = 0; j < LAZY_MAX_MUTEX; j++)
+		init_recursive_mutex(&lazy_dir_mutex_array[j]);
+}
+
+static void cleanup_dir_mutex(void)
+{
+	int j;
+
+	for (j = 0; j < LAZY_MAX_MUTEX; j++)
+		pthread_mutex_destroy(&lazy_dir_mutex_array[j]);
+
+	free(lazy_dir_mutex_array);
+}
+
+static void lock_dir_mutex(int j)
+{
+	pthread_mutex_lock(&lazy_dir_mutex_array[j]);
+}
+
+static void unlock_dir_mutex(int j)
+{
+	pthread_mutex_unlock(&lazy_dir_mutex_array[j]);
+}
+
+static inline int compute_dir_lock_nr(
+	const struct hashmap *map,
+	unsigned int hash)
+{
+	return hashmap_bucket(map, hash) % LAZY_MAX_MUTEX;
+}
+
+static struct dir_entry *hash_dir_entry_with_parent_and_prefix(
+	struct index_state *istate,
+	struct dir_entry *parent,
+	struct strbuf *prefix)
+{
+	struct dir_entry *dir;
+	unsigned int hash;
+	int lock_nr;
+
+	/*
+	 * Either we have a parent directory and path with slash(es)
+	 * or the directory is an immediate child of the root directory.
+	 */
+	assert((parent != NULL) ^ (strchr(prefix->buf, '/') == NULL));
+
+	if (parent)
+		hash = memihash_cont(parent->ent.hash,
+			prefix->buf + parent->namelen,
+			prefix->len - parent->namelen);
+	else
+		hash = memihash(prefix->buf, prefix->len);
+
+	lock_nr = compute_dir_lock_nr(&istate->dir_hash, hash);
+	lock_dir_mutex(lock_nr);
+
+	dir = find_dir_entry__hash(istate, prefix->buf, prefix->len, hash);
+	if (!dir) {
+		FLEX_ALLOC_MEM(dir, name, prefix->buf, prefix->len);
+		hashmap_entry_init(dir, hash);
+		dir->namelen = prefix->len;
+		dir->parent = parent;
+		hashmap_add(&istate->dir_hash, dir);
+
+		if (parent) {
+			unlock_dir_mutex(lock_nr);
+
+			/* All I really need here is an InterlockedIncrement(&(parent->nr)) */
+			lock_nr = compute_dir_lock_nr(&istate->dir_hash, parent->ent.hash);
+			lock_dir_mutex(lock_nr);
+			parent->nr++;
+		}
+	}
+
+	unlock_dir_mutex(lock_nr);
 
+	return dir;
+}
+
+/*
+ * handle_range_1() and handle_range_dir() are derived from
+ * clear_ce_flags_1() and clear_ce_flags_dir() in unpack-trees.c
+ * and handle the iteration over the entire array of index entries.
+ * They use recursion for adjacent entries in the same parent
+ * directory.
+ */
+static int handle_range_1(
+	struct index_state *istate,
+	int k_start,
+	int k_end,
+	struct dir_entry *parent,
+	struct strbuf *prefix,
+	struct lazy_entry *lazy_entries);
+
+static int handle_range_dir(
+	struct index_state *istate,
+	int k_start,
+	int k_end,
+	struct dir_entry *parent,
+	struct strbuf *prefix,
+	struct lazy_entry *lazy_entries,
+	struct dir_entry **dir_new_out)
+{
+	int rc, k;
+	int input_prefix_len = prefix->len;
+	struct dir_entry *dir_new;
+
+	dir_new = hash_dir_entry_with_parent_and_prefix(istate, parent, prefix);
+
+	strbuf_addch(prefix, '/');
+
+	/*
+	 * Scan forward in the index array for index entries having the same
+	 * path prefix (that are also in this directory).
+	 */
+	if (k_start + 1 >= k_end)
+		k = k_end;
+	else if (strncmp(istate->cache[k_start + 1]->name, prefix->buf, prefix->len) > 0)
+		k = k_start + 1;
+	else if (strncmp(istate->cache[k_end - 1]->name, prefix->buf, prefix->len) == 0)
+		k = k_end;
+	else {
+		int begin = k_start;
+		int end = k_end;
+		while (begin < end) {
+			int mid = (begin + end) >> 1;
+			int cmp = strncmp(istate->cache[mid]->name, prefix->buf, prefix->len);
+			if (cmp == 0) /* mid has same prefix; look in second part */
+				begin = mid + 1;
+			else if (cmp > 0) /* mid is past group; look in first part */
+				end = mid;
+			else
+				die("cache entry out of order");
+		}
+		k = begin;
+	}
+
+	/*
+	 * Recurse and process what we can of this subset [k_start, k).
+	 */
+	rc = handle_range_1(istate, k_start, k, dir_new, prefix, lazy_entries);
+
+	strbuf_setlen(prefix, input_prefix_len);
+
+	*dir_new_out = dir_new;
+	return rc;
+}
+
+static int handle_range_1(
+	struct index_state *istate,
+	int k_start,
+	int k_end,
+	struct dir_entry *parent,
+	struct strbuf *prefix,
+	struct lazy_entry *lazy_entries)
+{
+	int input_prefix_len = prefix->len;
+	int k = k_start;
+
+	while (k < k_end) {
+		struct cache_entry *ce_k = istate->cache[k];
+		const char *name, *slash;
+
+		if (prefix->len && strncmp(ce_k->name, prefix->buf, prefix->len))
+			break;
+
+		name = ce_k->name + prefix->len;
+		slash = strchr(name, '/');
+
+		if (slash) {
+			int len = slash - name;
+			int processed;
+			struct dir_entry *dir_new;
+
+			strbuf_add(prefix, name, len);
+			processed = handle_range_dir(istate, k, k_end, parent, prefix, lazy_entries, &dir_new);
+			if (processed) {
+				k += processed;
+				strbuf_setlen(prefix, input_prefix_len);
+				continue;
+			}
+
+			strbuf_addch(prefix, '/');
+			processed = handle_range_1(istate, k, k_end, dir_new, prefix, lazy_entries);
+			k += processed;
+			strbuf_setlen(prefix, input_prefix_len);
+			continue;
+		}
+
+		/*
+		 * It is too expensive to take a lock to insert "ce_k"
+		 * into "istate->name_hash" and increment the ref-count
+		 * on the "parent" dir.  So we defer actually updating
+		 * permanent data structures until phase 2 (where we
+		 * can change the locking requirements) and simply
+		 * accumulate our current results into the lazy_entries
+		 * data array).
+		 *
+		 * We do not need to lock the lazy_entries array because
+		 * we have exclusive access to the cells in the range
+		 * [k_start,k_end) that this thread was given.
+		 */
+		lazy_entries[k].dir = parent;
+		if (parent) {
+			lazy_entries[k].hash_name = memihash_cont(
+				parent->ent.hash,
+				ce_k->name + parent->namelen,
+				ce_namelen(ce_k) - parent->namelen);
+			lazy_entries[k].hash_dir = parent->ent.hash;
+		} else {
+			lazy_entries[k].hash_name = memihash(ce_k->name, ce_namelen(ce_k));
+		}
+
+		k++;
+	}
+
+	return k - k_start;
+}
+
+struct lazy_dir_thread_data {
+	pthread_t pthread;
+	struct index_state *istate;
+	struct lazy_entry *lazy_entries;
+	int k_start;
+	int k_end;
+};
+
+static void *lazy_dir_thread_proc(void *_data)
+{
+	struct lazy_dir_thread_data *d = _data;
+	struct strbuf prefix = STRBUF_INIT;
+	handle_range_1(d->istate, d->k_start, d->k_end, NULL, &prefix, d->lazy_entries);
+	strbuf_release(&prefix);
+	return NULL;
+}
+
+struct lazy_name_thread_data {
+	pthread_t pthread;
+	struct index_state *istate;
+	struct lazy_entry *lazy_entries;
+};
+
+static void *lazy_name_thread_proc(void *_data)
+{
+	struct lazy_name_thread_data *d = _data;
+	int k;
+
+	for (k = 0; k < d->istate->cache_nr; k++) {
+		struct cache_entry *ce_k = d->istate->cache[k];
+		ce_k->ce_flags |= CE_HASHED;
+		hashmap_entry_init(ce_k, d->lazy_entries[k].hash_name);
+		hashmap_add(&d->istate->name_hash, ce_k);
+	}
+
+	return NULL;
+}
+
+static inline void lazy_update_dir_ref_counts(
+	struct index_state *istate,
+	struct lazy_entry *lazy_entries)
+{
+	int k;
+
+	for (k = 0; k < istate->cache_nr; k++) {
+		if (lazy_entries[k].dir)
+			lazy_entries[k].dir->nr++;
+	}
+}
+
+static void threaded_lazy_init_name_hash(
+	struct index_state *istate)
+{
+	int nr_each;
+	int k_start;
+	int t;
+	struct lazy_entry *lazy_entries;
+	struct lazy_dir_thread_data *td_dir;
+	struct lazy_name_thread_data *td_name;
+
+	k_start = 0;
+	nr_each = DIV_ROUND_UP(istate->cache_nr, lazy_nr_dir_threads);
+
+	lazy_entries = xcalloc(istate->cache_nr, sizeof(struct lazy_entry));
+	td_dir = xcalloc(lazy_nr_dir_threads, sizeof(struct lazy_dir_thread_data));
+	td_name = xcalloc(1, sizeof(struct lazy_name_thread_data));
+
+	init_dir_mutex();
+
+	/*
+	 * Phase 1:
+	 * Build "istate->dir_hash" using n "dir" threads (and a read-only index).
+	 */
+	for (t = 0; t < lazy_nr_dir_threads; t++) {
+		struct lazy_dir_thread_data *td_dir_t = td_dir + t;
+		td_dir_t->istate = istate;
+		td_dir_t->lazy_entries = lazy_entries;
+		td_dir_t->k_start = k_start;
+		k_start += nr_each;
+		if (k_start > istate->cache_nr)
+			k_start = istate->cache_nr;
+		td_dir_t->k_end = k_start;
+		if (pthread_create(&td_dir_t->pthread, NULL, lazy_dir_thread_proc, td_dir_t))
+			die("unable to create lazy_dir_thread");
+	}
+	for (t = 0; t < lazy_nr_dir_threads; t++) {
+		struct lazy_dir_thread_data *td_dir_t = td_dir + t;
+		if (pthread_join(td_dir_t->pthread, NULL))
+			die("unable to join lazy_dir_thread");
+	}
+
+	/*
+	 * Phase 2:
+	 * Iterate over all index entries and add them to the "istate->name_hash"
+	 * using a single "name" background thread.
+	 * (Testing showed it wasn't worth running more than 1 thread for this.)
+	 *
+	 * Meanwhile, finish updating the parent directory ref-counts for each
+	 * index entry using the current thread.  (This step is very fast and
+	 * doesn't need threading.)
+	 */
+	td_name->istate = istate;
+	td_name->lazy_entries = lazy_entries;
+	if (pthread_create(&td_name->pthread, NULL, lazy_name_thread_proc, td_name))
+		die("unable to create lazy_name_thread");
+
+	lazy_update_dir_ref_counts(istate, lazy_entries);
+
+	if (pthread_join(td_name->pthread, NULL))
+		die("unable to join lazy_name_thread");
+
+	cleanup_dir_mutex();
+
+	free(td_name);
+	free(td_dir);
+	free(lazy_entries);
+}
+
+#endif
+
+static void lazy_init_name_hash(struct index_state *istate)
+{
 	if (istate->name_hash_initialized)
 		return;
 	hashmap_init(&istate->name_hash, (hashmap_cmp_fn) cache_entry_cmp,
 			istate->cache_nr);
-	hashmap_init(&istate->dir_hash, (hashmap_cmp_fn) dir_entry_cmp, 0);
-	for (nr = 0; nr < istate->cache_nr; nr++)
-		hash_index_entry(istate, istate->cache[nr]);
+	hashmap_init(&istate->dir_hash, (hashmap_cmp_fn) dir_entry_cmp,
+			istate->cache_nr);
+
+	if (lookup_lazy_params(istate)) {
+		hashmap_disallow_rehash(&istate->dir_hash, 1);
+		threaded_lazy_init_name_hash(istate);
+		hashmap_disallow_rehash(&istate->dir_hash, 0);
+	} else {
+		int nr;
+		for (nr = 0; nr < istate->cache_nr; nr++)
+			hash_index_entry(istate, istate->cache[nr]);
+	}
+
 	istate->name_hash_initialized = 1;
 }
 
+/*
+ * A test routine for t/helper/ sources.
+ *
+ * Returns the number of threads used or 0 when
+ * the non-threaded code path was used.
+ *
+ * Requesting threading WILL NOT override guards
+ * in lookup_lazy_params().
+ */
+int test_lazy_init_name_hash(struct index_state *istate, int try_threaded)
+{
+	lazy_nr_dir_threads = 0;
+	lazy_try_threaded = try_threaded;
+
+	lazy_init_name_hash(istate);
+
+	return lazy_nr_dir_threads;
+}
+
 void add_name_hash(struct index_state *istate, struct cache_entry *ce)
 {
 	if (istate->name_hash_initialized)