preload-index.c

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