preload-index.c

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