preload-index.c

   1 /*
   2  * Copyright (C) 2008 Linus Torvalds
   3  */
   4 #include "cache.h"
   5 #include "pathspec.h"
   6 #include "dir.h"
   7
   8 #ifdef NO_PTHREADS
   9 static void preload_index(struct index_state *index,
  10                           const struct pathspec *pathspec)
  11 {
  12         ; /* nothing */
  13 }
  14 #else
  15
  16 #include <pthread.h>
  17
  18 /*
  19  * Mostly randomly chosen maximum thread counts: we
  20  * cap the parallelism to 20 threads, and we want
  21  * to have at least 500 lstat's per thread for it to
  22  * be worth starting a thread.
  23  */
  24 #define MAX_PARALLEL (20)
  25 #define THREAD_COST (500)
  26
  27 struct thread_data {
  28         pthread_t pthread;
  29         struct index_state *index;
  30         struct pathspec pathspec;
  31         int offset, nr;
  32 };
  33
  34 static void *preload_thread(void *_data)
  35 {
  36         int nr;
  37         struct thread_data *p = _data;
  38         struct index_state *index = p->index;
  39         struct cache_entry **cep = index->cache + p->offset;
  40         struct cache_def cache = CACHE_DEF_INIT;
  41
  42         nr = p->nr;
  43         if (nr + p->offset > index->cache_nr)
  44                 nr = index->cache_nr - p->offset;
  45
  46         do {
  47                 struct cache_entry *ce = *cep++;
  48                 struct stat st;
  49
  50                 if (ce_stage(ce))
  51                         continue;
  52                 if (S_ISGITLINK(ce->ce_mode))
  53                         continue;
  54                 if (ce_uptodate(ce))
  55                         continue;
  56                 if (ce_skip_worktree(ce))
  57                         continue;
  58                 if (!ce_path_match(ce, &p->pathspec, NULL))
  59                         continue;
  60                 if (threaded_has_symlink_leading_path(&cache, ce->name, ce_namelen(ce)))
  61                         continue;
  62                 if (lstat(ce->name, &st))
  63                         continue;
  64                 if (ie_match_stat(index, ce, &st, CE_MATCH_RACY_IS_DIRTY))
  65                         continue;
  66                 ce_mark_uptodate(ce);
  67         } while (--nr > 0);
  68         cache_def_clear(&cache);
  69         return NULL;
  70 }
  71
  72 static void preload_index(struct index_state *index,
  73                           const struct pathspec *pathspec)
  74 {
  75         int threads, i, work, offset;
  76         struct thread_data data[MAX_PARALLEL];
  77
  78         if (!core_preload_index)
  79                 return;
  80
  81         threads = index->cache_nr / THREAD_COST;
  82         if (threads < 2)
  83                 return;
  84         if (threads > MAX_PARALLEL)
  85                 threads = MAX_PARALLEL;
  86         offset = 0;
  87         work = DIV_ROUND_UP(index->cache_nr, threads);
  88         memset(&data, 0, sizeof(data));
  89         for (i = 0; i < threads; i++) {
  90                 struct thread_data *p = data+i;
  91                 p->index = index;
  92                 if (pathspec)
  93                         copy_pathspec(&p->pathspec, pathspec);
  94                 p->offset = offset;
  95                 p->nr = work;
  96                 offset += work;
  97                 if (pthread_create(&p->pthread, NULL, preload_thread, p))
  98                         die("unable to create threaded lstat");
  99         }
 100         for (i = 0; i < threads; i++) {
 101                 struct thread_data *p = data+i;
 102                 if (pthread_join(p->pthread, NULL))
 103                         die("unable to join threaded lstat");
 104         }
 105 }
 106 #endif
 107
 108 int read_index_preload(struct index_state *index,
 109                        const struct pathspec *pathspec)
 110 {
 111         int retval = read_index(index);
 112
 113         preload_index(index, pathspec);
 114         return retval;
 115 }