summaryrefslogtreecommitdiff
path: root/preload-index.c
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2008-11-14 00:36:30 (GMT)
committerJunio C Hamano <gitster@pobox.com>2008-11-15 03:11:49 (GMT)
commit671c9b7e315db89081cc69f83a8f405e4aca37bc (patch)
tree0410fb1af855fc65a7d96dd15410db16e41cbc9f /preload-index.c
parenta0d3ab9c277f1a198ec8e29432c0127d4cf719d2 (diff)
downloadgit-671c9b7e315db89081cc69f83a8f405e4aca37bc.zip
git-671c9b7e315db89081cc69f83a8f405e4aca37bc.tar.gz
git-671c9b7e315db89081cc69f83a8f405e4aca37bc.tar.bz2
Add cache preload facility
This can do the lstat() storm in parallel, giving potentially much improved performance for cold-cache cases or things like NFS that have weak metadata caching. Just use "read_cache_preload()" instead of "read_cache()" to force an optimistic preload of the index stat data. The function takes a pathspec as its argument, allowing us to preload only the relevant portion of the index. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'preload-index.c')
-rw-r--r--preload-index.c91
1 files changed, 91 insertions, 0 deletions
diff --git a/preload-index.c b/preload-index.c
new file mode 100644
index 0000000..6253578
--- /dev/null
+++ b/preload-index.c
@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2008 Linus Torvalds
+ */
+#include "cache.h"
+#include <pthread.h>
+
+/*
+ * Mostly randomly chosen maximum thread counts: we
+ * cap the parallelism to 20 threads, and we want
+ * to have at least 500 lstat's per thread for it to
+ * be worth starting a thread.
+ */
+#define MAX_PARALLEL (20)
+#define THREAD_COST (500)
+
+struct thread_data {
+ pthread_t pthread;
+ struct index_state *index;
+ const char **pathspec;
+ int offset, nr;
+};
+
+static void *preload_thread(void *_data)
+{
+ int nr;
+ struct thread_data *p = _data;
+ struct index_state *index = p->index;
+ struct cache_entry **cep = index->cache + p->offset;
+
+ nr = p->nr;
+ if (nr + p->offset > index->cache_nr)
+ nr = index->cache_nr - p->offset;
+
+ do {
+ struct cache_entry *ce = *cep++;
+ struct stat st;
+
+ if (ce_stage(ce))
+ continue;
+ if (ce_uptodate(ce))
+ continue;
+ if (!ce_path_match(ce, p->pathspec))
+ continue;
+ if (lstat(ce->name, &st))
+ continue;
+ if (ie_match_stat(index, ce, &st, 0))
+ continue;
+ ce_mark_uptodate(ce);
+ } while (--nr > 0);
+ return NULL;
+}
+
+static void preload_index(struct index_state *index, const char **pathspec)
+{
+ int threads, i, work, offset;
+ struct thread_data data[MAX_PARALLEL];
+
+ if (!core_preload_index)
+ return;
+
+ threads = index->cache_nr / THREAD_COST;
+ if (threads < 2)
+ return;
+ if (threads > MAX_PARALLEL)
+ threads = MAX_PARALLEL;
+ offset = 0;
+ work = (index->cache_nr + threads - 1) / threads;
+ for (i = 0; i < threads; i++) {
+ struct thread_data *p = data+i;
+ p->index = index;
+ p->pathspec = pathspec;
+ p->offset = offset;
+ p->nr = work;
+ offset += work;
+ if (pthread_create(&p->pthread, NULL, preload_thread, p))
+ die("unable to create threaded lstat");
+ }
+ for (i = 0; i < threads; i++) {
+ struct thread_data *p = data+i;
+ if (pthread_join(p->pthread, NULL))
+ die("unable to join threaded lstat");
+ }
+}
+
+int read_index_preload(struct index_state *index, const char **pathspec)
+{
+ int retval = read_index(index);
+
+ preload_index(index, pathspec);
+ return retval;
+}