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