root/preload-index.c

DEFINITIONS

1. preload_index
2. preload_thread
3. preload_index
4. read_index_preload

/*
 * Copyright (C) 2008 Linus Torvalds
 */
#include "cache.h"
#include "pathspec.h"
#include "dir.h"

#ifdef NO_PTHREADS
static void preload_index(struct index_state *index,
                          const struct pathspec *pathspec)
{
        ; /* nothing */
}
#else

#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;
        struct pathspec 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;
        struct cache_def cache = CACHE_DEF_INIT;

        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 (S_ISGITLINK(ce->ce_mode))
                        continue;
                if (ce_uptodate(ce))
                        continue;
                if (!ce_path_match(ce, &p->pathspec, NULL))
                        continue;
                if (threaded_has_symlink_leading_path(&cache, ce->name, ce_namelen(ce)))
                        continue;
                if (lstat(ce->name, &st))
                        continue;
                if (ie_match_stat(index, ce, &st, CE_MATCH_RACY_IS_DIRTY))
                        continue;
                ce_mark_uptodate(ce);
        } while (--nr > 0);
        cache_def_clear(&cache);
        return NULL;
}

static void preload_index(struct index_state *index,
                          const struct pathspec *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 = DIV_ROUND_UP(index->cache_nr, threads);
        memset(&data, 0, sizeof(data));
        for (i = 0; i < threads; i++) {
                struct thread_data *p = data+i;
                p->index = index;
                if (pathspec)
                        copy_pathspec(&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");
        }
}
#endif

int read_index_preload(struct index_state *index,
                       const struct pathspec *pathspec)
{
        int retval = read_index(index);

        preload_index(index, pathspec);
        return retval;
}