transport-helper: drop read/write errno checks
[git.git] / name-hash.c
blob623ca6923a9ec78b9bb7d7cc899af72057d101d3
1 /*
2 * name-hash.c
4 * Hashing names in the index state
6 * Copyright (C) 2008 Linus Torvalds
7 */
8 #define NO_THE_INDEX_COMPATIBILITY_MACROS
9 #include "cache.h"
10 #include "thread-utils.h"
12 struct dir_entry {
13 struct hashmap_entry ent;
14 struct dir_entry *parent;
15 int nr;
16 unsigned int namelen;
17 char name[FLEX_ARRAY];
20 static int dir_entry_cmp(const void *unused_cmp_data,
21 const void *entry,
22 const void *entry_or_key,
23 const void *keydata)
25 const struct dir_entry *e1 = entry;
26 const struct dir_entry *e2 = entry_or_key;
27 const char *name = keydata;
29 return e1->namelen != e2->namelen || strncasecmp(e1->name,
30 name ? name : e2->name, e1->namelen);
33 static struct dir_entry *find_dir_entry__hash(struct index_state *istate,
34 const char *name, unsigned int namelen, unsigned int hash)
36 struct dir_entry key;
37 hashmap_entry_init(&key, hash);
38 key.namelen = namelen;
39 return hashmap_get(&istate->dir_hash, &key, name);
42 static struct dir_entry *find_dir_entry(struct index_state *istate,
43 const char *name, unsigned int namelen)
45 return find_dir_entry__hash(istate, name, namelen, memihash(name, namelen));
48 static struct dir_entry *hash_dir_entry(struct index_state *istate,
49 struct cache_entry *ce, int namelen)
52 * Throw each directory component in the hash for quick lookup
53 * during a git status. Directory components are stored without their
54 * closing slash. Despite submodules being a directory, they never
55 * reach this point, because they are stored
56 * in index_state.name_hash (as ordinary cache_entries).
58 struct dir_entry *dir;
60 /* get length of parent directory */
61 while (namelen > 0 && !is_dir_sep(ce->name[namelen - 1]))
62 namelen--;
63 if (namelen <= 0)
64 return NULL;
65 namelen--;
67 /* lookup existing entry for that directory */
68 dir = find_dir_entry(istate, ce->name, namelen);
69 if (!dir) {
70 /* not found, create it and add to hash table */
71 FLEX_ALLOC_MEM(dir, name, ce->name, namelen);
72 hashmap_entry_init(dir, memihash(ce->name, namelen));
73 dir->namelen = namelen;
74 hashmap_add(&istate->dir_hash, dir);
76 /* recursively add missing parent directories */
77 dir->parent = hash_dir_entry(istate, ce, namelen);
79 return dir;
82 static void add_dir_entry(struct index_state *istate, struct cache_entry *ce)
84 /* Add reference to the directory entry (and parents if 0). */
85 struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
86 while (dir && !(dir->nr++))
87 dir = dir->parent;
90 static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)
93 * Release reference to the directory entry. If 0, remove and continue
94 * with parent directory.
96 struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
97 while (dir && !(--dir->nr)) {
98 struct dir_entry *parent = dir->parent;
99 hashmap_remove(&istate->dir_hash, dir, NULL);
100 free(dir);
101 dir = parent;
105 static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
107 if (ce->ce_flags & CE_HASHED)
108 return;
109 ce->ce_flags |= CE_HASHED;
110 hashmap_entry_init(ce, memihash(ce->name, ce_namelen(ce)));
111 hashmap_add(&istate->name_hash, ce);
113 if (ignore_case)
114 add_dir_entry(istate, ce);
117 static int cache_entry_cmp(const void *unused_cmp_data,
118 const void *entry,
119 const void *entry_or_key,
120 const void *remove)
122 const struct cache_entry *ce1 = entry;
123 const struct cache_entry *ce2 = entry_or_key;
125 * For remove_name_hash, find the exact entry (pointer equality); for
126 * index_file_exists, find all entries with matching hash code and
127 * decide whether the entry matches in same_name.
129 return remove ? !(ce1 == ce2) : 0;
132 static int lazy_try_threaded = 1;
133 static int lazy_nr_dir_threads;
136 * Set a minimum number of cache_entries that we will handle per
137 * thread and use that to decide how many threads to run (upto
138 * the number on the system).
140 * For guidance setting the lower per-thread bound, see:
141 * t/helper/test-lazy-init-name-hash --analyze
143 #define LAZY_THREAD_COST (2000)
146 * We use n mutexes to guard n partitions of the "istate->dir_hash"
147 * hashtable. Since "find" and "insert" operations will hash to a
148 * particular bucket and modify/search a single chain, we can say
149 * that "all chains mod n" are guarded by the same mutex -- rather
150 * than having a single mutex to guard the entire table. (This does
151 * require that we disable "rehashing" on the hashtable.)
153 * So, a larger value here decreases the probability of a collision
154 * and the time that each thread must wait for the mutex.
156 #define LAZY_MAX_MUTEX (32)
158 static pthread_mutex_t *lazy_dir_mutex_array;
161 * An array of lazy_entry items is used by the n threads in
162 * the directory parse (first) phase to (lock-free) store the
163 * intermediate results. These values are then referenced by
164 * the 2 threads in the second phase.
166 struct lazy_entry {
167 struct dir_entry *dir;
168 unsigned int hash_dir;
169 unsigned int hash_name;
173 * Decide if we want to use threads (if available) to load
174 * the hash tables. We set "lazy_nr_dir_threads" to zero when
175 * it is not worth it.
177 static int lookup_lazy_params(struct index_state *istate)
179 int nr_cpus;
181 lazy_nr_dir_threads = 0;
183 if (!lazy_try_threaded)
184 return 0;
187 * If we are respecting case, just use the original
188 * code to build the "istate->name_hash". We don't
189 * need the complexity here.
191 if (!ignore_case)
192 return 0;
194 nr_cpus = online_cpus();
195 if (nr_cpus < 2)
196 return 0;
198 if (istate->cache_nr < 2 * LAZY_THREAD_COST)
199 return 0;
201 if (istate->cache_nr < nr_cpus * LAZY_THREAD_COST)
202 nr_cpus = istate->cache_nr / LAZY_THREAD_COST;
203 lazy_nr_dir_threads = nr_cpus;
204 return lazy_nr_dir_threads;
208 * Initialize n mutexes for use when searching and inserting
209 * into "istate->dir_hash". All "dir" threads are trying
210 * to insert partial pathnames into the hash as they iterate
211 * over their portions of the index, so lock contention is
212 * high.
214 * However, the hashmap is going to put items into bucket
215 * chains based on their hash values. Use that to create n
216 * mutexes and lock on mutex[bucket(hash) % n]. This will
217 * decrease the collision rate by (hopefully) by a factor of n.
219 static void init_dir_mutex(void)
221 int j;
223 lazy_dir_mutex_array = xcalloc(LAZY_MAX_MUTEX, sizeof(pthread_mutex_t));
225 for (j = 0; j < LAZY_MAX_MUTEX; j++)
226 init_recursive_mutex(&lazy_dir_mutex_array[j]);
229 static void cleanup_dir_mutex(void)
231 int j;
233 for (j = 0; j < LAZY_MAX_MUTEX; j++)
234 pthread_mutex_destroy(&lazy_dir_mutex_array[j]);
236 free(lazy_dir_mutex_array);
239 static void lock_dir_mutex(int j)
241 pthread_mutex_lock(&lazy_dir_mutex_array[j]);
244 static void unlock_dir_mutex(int j)
246 pthread_mutex_unlock(&lazy_dir_mutex_array[j]);
249 static inline int compute_dir_lock_nr(
250 const struct hashmap *map,
251 unsigned int hash)
253 return hashmap_bucket(map, hash) % LAZY_MAX_MUTEX;
256 static struct dir_entry *hash_dir_entry_with_parent_and_prefix(
257 struct index_state *istate,
258 struct dir_entry *parent,
259 struct strbuf *prefix)
261 struct dir_entry *dir;
262 unsigned int hash;
263 int lock_nr;
266 * Either we have a parent directory and path with slash(es)
267 * or the directory is an immediate child of the root directory.
269 assert((parent != NULL) ^ (strchr(prefix->buf, '/') == NULL));
271 if (parent)
272 hash = memihash_cont(parent->ent.hash,
273 prefix->buf + parent->namelen,
274 prefix->len - parent->namelen);
275 else
276 hash = memihash(prefix->buf, prefix->len);
278 lock_nr = compute_dir_lock_nr(&istate->dir_hash, hash);
279 lock_dir_mutex(lock_nr);
281 dir = find_dir_entry__hash(istate, prefix->buf, prefix->len, hash);
282 if (!dir) {
283 FLEX_ALLOC_MEM(dir, name, prefix->buf, prefix->len);
284 hashmap_entry_init(dir, hash);
285 dir->namelen = prefix->len;
286 dir->parent = parent;
287 hashmap_add(&istate->dir_hash, dir);
289 if (parent) {
290 unlock_dir_mutex(lock_nr);
292 /* All I really need here is an InterlockedIncrement(&(parent->nr)) */
293 lock_nr = compute_dir_lock_nr(&istate->dir_hash, parent->ent.hash);
294 lock_dir_mutex(lock_nr);
295 parent->nr++;
299 unlock_dir_mutex(lock_nr);
301 return dir;
305 * handle_range_1() and handle_range_dir() are derived from
306 * clear_ce_flags_1() and clear_ce_flags_dir() in unpack-trees.c
307 * and handle the iteration over the entire array of index entries.
308 * They use recursion for adjacent entries in the same parent
309 * directory.
311 static int handle_range_1(
312 struct index_state *istate,
313 int k_start,
314 int k_end,
315 struct dir_entry *parent,
316 struct strbuf *prefix,
317 struct lazy_entry *lazy_entries);
319 static int handle_range_dir(
320 struct index_state *istate,
321 int k_start,
322 int k_end,
323 struct dir_entry *parent,
324 struct strbuf *prefix,
325 struct lazy_entry *lazy_entries,
326 struct dir_entry **dir_new_out)
328 int rc, k;
329 int input_prefix_len = prefix->len;
330 struct dir_entry *dir_new;
332 dir_new = hash_dir_entry_with_parent_and_prefix(istate, parent, prefix);
334 strbuf_addch(prefix, '/');
337 * Scan forward in the index array for index entries having the same
338 * path prefix (that are also in this directory).
340 if (k_start + 1 >= k_end)
341 k = k_end;
342 else if (strncmp(istate->cache[k_start + 1]->name, prefix->buf, prefix->len) > 0)
343 k = k_start + 1;
344 else if (strncmp(istate->cache[k_end - 1]->name, prefix->buf, prefix->len) == 0)
345 k = k_end;
346 else {
347 int begin = k_start;
348 int end = k_end;
349 while (begin < end) {
350 int mid = (begin + end) >> 1;
351 int cmp = strncmp(istate->cache[mid]->name, prefix->buf, prefix->len);
352 if (cmp == 0) /* mid has same prefix; look in second part */
353 begin = mid + 1;
354 else if (cmp > 0) /* mid is past group; look in first part */
355 end = mid;
356 else
357 die("cache entry out of order");
359 k = begin;
363 * Recurse and process what we can of this subset [k_start, k).
365 rc = handle_range_1(istate, k_start, k, dir_new, prefix, lazy_entries);
367 strbuf_setlen(prefix, input_prefix_len);
369 *dir_new_out = dir_new;
370 return rc;
373 static int handle_range_1(
374 struct index_state *istate,
375 int k_start,
376 int k_end,
377 struct dir_entry *parent,
378 struct strbuf *prefix,
379 struct lazy_entry *lazy_entries)
381 int input_prefix_len = prefix->len;
382 int k = k_start;
384 while (k < k_end) {
385 struct cache_entry *ce_k = istate->cache[k];
386 const char *name, *slash;
388 if (prefix->len && strncmp(ce_k->name, prefix->buf, prefix->len))
389 break;
391 name = ce_k->name + prefix->len;
392 slash = strchr(name, '/');
394 if (slash) {
395 int len = slash - name;
396 int processed;
397 struct dir_entry *dir_new;
399 strbuf_add(prefix, name, len);
400 processed = handle_range_dir(istate, k, k_end, parent, prefix, lazy_entries, &dir_new);
401 if (processed) {
402 k += processed;
403 strbuf_setlen(prefix, input_prefix_len);
404 continue;
407 strbuf_addch(prefix, '/');
408 processed = handle_range_1(istate, k, k_end, dir_new, prefix, lazy_entries);
409 k += processed;
410 strbuf_setlen(prefix, input_prefix_len);
411 continue;
415 * It is too expensive to take a lock to insert "ce_k"
416 * into "istate->name_hash" and increment the ref-count
417 * on the "parent" dir. So we defer actually updating
418 * permanent data structures until phase 2 (where we
419 * can change the locking requirements) and simply
420 * accumulate our current results into the lazy_entries
421 * data array).
423 * We do not need to lock the lazy_entries array because
424 * we have exclusive access to the cells in the range
425 * [k_start,k_end) that this thread was given.
427 lazy_entries[k].dir = parent;
428 if (parent) {
429 lazy_entries[k].hash_name = memihash_cont(
430 parent->ent.hash,
431 ce_k->name + parent->namelen,
432 ce_namelen(ce_k) - parent->namelen);
433 lazy_entries[k].hash_dir = parent->ent.hash;
434 } else {
435 lazy_entries[k].hash_name = memihash(ce_k->name, ce_namelen(ce_k));
438 k++;
441 return k - k_start;
444 struct lazy_dir_thread_data {
445 pthread_t pthread;
446 struct index_state *istate;
447 struct lazy_entry *lazy_entries;
448 int k_start;
449 int k_end;
452 static void *lazy_dir_thread_proc(void *_data)
454 struct lazy_dir_thread_data *d = _data;
455 struct strbuf prefix = STRBUF_INIT;
456 handle_range_1(d->istate, d->k_start, d->k_end, NULL, &prefix, d->lazy_entries);
457 strbuf_release(&prefix);
458 return NULL;
461 struct lazy_name_thread_data {
462 pthread_t pthread;
463 struct index_state *istate;
464 struct lazy_entry *lazy_entries;
467 static void *lazy_name_thread_proc(void *_data)
469 struct lazy_name_thread_data *d = _data;
470 int k;
472 for (k = 0; k < d->istate->cache_nr; k++) {
473 struct cache_entry *ce_k = d->istate->cache[k];
474 ce_k->ce_flags |= CE_HASHED;
475 hashmap_entry_init(ce_k, d->lazy_entries[k].hash_name);
476 hashmap_add(&d->istate->name_hash, ce_k);
479 return NULL;
482 static inline void lazy_update_dir_ref_counts(
483 struct index_state *istate,
484 struct lazy_entry *lazy_entries)
486 int k;
488 for (k = 0; k < istate->cache_nr; k++) {
489 if (lazy_entries[k].dir)
490 lazy_entries[k].dir->nr++;
494 static void threaded_lazy_init_name_hash(
495 struct index_state *istate)
497 int err;
498 int nr_each;
499 int k_start;
500 int t;
501 struct lazy_entry *lazy_entries;
502 struct lazy_dir_thread_data *td_dir;
503 struct lazy_name_thread_data *td_name;
505 if (!HAVE_THREADS)
506 return;
508 k_start = 0;
509 nr_each = DIV_ROUND_UP(istate->cache_nr, lazy_nr_dir_threads);
511 lazy_entries = xcalloc(istate->cache_nr, sizeof(struct lazy_entry));
512 td_dir = xcalloc(lazy_nr_dir_threads, sizeof(struct lazy_dir_thread_data));
513 td_name = xcalloc(1, sizeof(struct lazy_name_thread_data));
515 init_dir_mutex();
518 * Phase 1:
519 * Build "istate->dir_hash" using n "dir" threads (and a read-only index).
521 for (t = 0; t < lazy_nr_dir_threads; t++) {
522 struct lazy_dir_thread_data *td_dir_t = td_dir + t;
523 td_dir_t->istate = istate;
524 td_dir_t->lazy_entries = lazy_entries;
525 td_dir_t->k_start = k_start;
526 k_start += nr_each;
527 if (k_start > istate->cache_nr)
528 k_start = istate->cache_nr;
529 td_dir_t->k_end = k_start;
530 err = pthread_create(&td_dir_t->pthread, NULL, lazy_dir_thread_proc, td_dir_t);
531 if (err)
532 die(_("unable to create lazy_dir thread: %s"), strerror(err));
534 for (t = 0; t < lazy_nr_dir_threads; t++) {
535 struct lazy_dir_thread_data *td_dir_t = td_dir + t;
536 if (pthread_join(td_dir_t->pthread, NULL))
537 die("unable to join lazy_dir_thread");
541 * Phase 2:
542 * Iterate over all index entries and add them to the "istate->name_hash"
543 * using a single "name" background thread.
544 * (Testing showed it wasn't worth running more than 1 thread for this.)
546 * Meanwhile, finish updating the parent directory ref-counts for each
547 * index entry using the current thread. (This step is very fast and
548 * doesn't need threading.)
550 td_name->istate = istate;
551 td_name->lazy_entries = lazy_entries;
552 err = pthread_create(&td_name->pthread, NULL, lazy_name_thread_proc, td_name);
553 if (err)
554 die(_("unable to create lazy_name thread: %s"), strerror(err));
556 lazy_update_dir_ref_counts(istate, lazy_entries);
558 err = pthread_join(td_name->pthread, NULL);
559 if (err)
560 die(_("unable to join lazy_name thread: %s"), strerror(err));
562 cleanup_dir_mutex();
564 free(td_name);
565 free(td_dir);
566 free(lazy_entries);
569 static void lazy_init_name_hash(struct index_state *istate)
572 if (istate->name_hash_initialized)
573 return;
574 trace_performance_enter();
575 hashmap_init(&istate->name_hash, cache_entry_cmp, NULL, istate->cache_nr);
576 hashmap_init(&istate->dir_hash, dir_entry_cmp, NULL, istate->cache_nr);
578 if (lookup_lazy_params(istate)) {
580 * Disable item counting and automatic rehashing because
581 * we do per-chain (mod n) locking rather than whole hashmap
582 * locking and we need to prevent the table-size from changing
583 * and bucket items from being redistributed.
585 hashmap_disable_item_counting(&istate->dir_hash);
586 threaded_lazy_init_name_hash(istate);
587 hashmap_enable_item_counting(&istate->dir_hash);
588 } else {
589 int nr;
590 for (nr = 0; nr < istate->cache_nr; nr++)
591 hash_index_entry(istate, istate->cache[nr]);
594 istate->name_hash_initialized = 1;
595 trace_performance_leave("initialize name hash");
599 * A test routine for t/helper/ sources.
601 * Returns the number of threads used or 0 when
602 * the non-threaded code path was used.
604 * Requesting threading WILL NOT override guards
605 * in lookup_lazy_params().
607 int test_lazy_init_name_hash(struct index_state *istate, int try_threaded)
609 lazy_nr_dir_threads = 0;
610 lazy_try_threaded = try_threaded;
612 lazy_init_name_hash(istate);
614 return lazy_nr_dir_threads;
617 void add_name_hash(struct index_state *istate, struct cache_entry *ce)
619 if (istate->name_hash_initialized)
620 hash_index_entry(istate, ce);
623 void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
625 if (!istate->name_hash_initialized || !(ce->ce_flags & CE_HASHED))
626 return;
627 ce->ce_flags &= ~CE_HASHED;
628 hashmap_remove(&istate->name_hash, ce, ce);
630 if (ignore_case)
631 remove_dir_entry(istate, ce);
634 static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
636 if (len1 != len2)
637 return 0;
639 while (len1) {
640 unsigned char c1 = *name1++;
641 unsigned char c2 = *name2++;
642 len1--;
643 if (c1 != c2) {
644 c1 = toupper(c1);
645 c2 = toupper(c2);
646 if (c1 != c2)
647 return 0;
650 return 1;
653 static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
655 int len = ce_namelen(ce);
658 * Always do exact compare, even if we want a case-ignoring comparison;
659 * we do the quick exact one first, because it will be the common case.
661 if (len == namelen && !memcmp(name, ce->name, len))
662 return 1;
664 if (!icase)
665 return 0;
667 return slow_same_name(name, namelen, ce->name, len);
670 int index_dir_exists(struct index_state *istate, const char *name, int namelen)
672 struct dir_entry *dir;
674 lazy_init_name_hash(istate);
675 dir = find_dir_entry(istate, name, namelen);
676 return dir && dir->nr;
679 void adjust_dirname_case(struct index_state *istate, char *name)
681 const char *startPtr = name;
682 const char *ptr = startPtr;
684 lazy_init_name_hash(istate);
685 while (*ptr) {
686 while (*ptr && *ptr != '/')
687 ptr++;
689 if (*ptr == '/') {
690 struct dir_entry *dir;
692 dir = find_dir_entry(istate, name, ptr - name);
693 if (dir) {
694 memcpy((void *)startPtr, dir->name + (startPtr - name), ptr - startPtr);
695 startPtr = ptr + 1;
697 ptr++;
702 struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
704 struct cache_entry *ce;
706 lazy_init_name_hash(istate);
708 ce = hashmap_get_from_hash(&istate->name_hash,
709 memihash(name, namelen), NULL);
710 while (ce) {
711 if (same_name(ce, name, namelen, icase))
712 return ce;
713 ce = hashmap_get_next(&istate->name_hash, ce);
715 return NULL;
718 void free_name_hash(struct index_state *istate)
720 if (!istate->name_hash_initialized)
721 return;
722 istate->name_hash_initialized = 0;
724 hashmap_free(&istate->name_hash, 0);
725 hashmap_free(&istate->dir_hash, 1);