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 (ce_uptodate(ce))
  51                         continue;
  52                 if (!ce_path_match(ce, p->pathspec))
  53                         continue;
  54                 if (threaded_has_symlink_leading_path(&cache, ce->name, ce_namelen(ce)))
  55                         continue;
  56                 if (lstat(ce->name, &st))
  57                         continue;
  58                 if (ie_match_stat(index, ce, &st, CE_MATCH_RACY_IS_DIRTY))
  59                         continue;
  60                 ce_mark_uptodate(ce);
  61         } while (--nr > 0);
  62         return NULL;
  63 }
  64
  65 static void preload_index(struct index_state *index, const char **pathspec)
  66 {
  67         int threads, i, work, offset;
  68         struct thread_data data[MAX_PARALLEL];
  69
  70         if (!core_preload_index)
  71                 return;
  72
  73         threads = index->cache_nr / THREAD_COST;
  74         if (threads < 2)
  75                 return;
  76         if (threads > MAX_PARALLEL)
  77                 threads = MAX_PARALLEL;
  78         offset = 0;
  79         work = DIV_ROUND_UP(index->cache_nr, threads);
  80         for (i = 0; i < threads; i++) {
  81                 struct thread_data *p = data+i;
  82                 p->index = index;
  83                 p->pathspec = pathspec;
  84                 p->offset = offset;
  85                 p->nr = work;
  86                 offset += work;
  87                 if (pthread_create(&p->pthread, NULL, preload_thread, p))
  88                         die("unable to create threaded lstat");
  89         }
  90         for (i = 0; i < threads; i++) {
  91                 struct thread_data *p = data+i;
  92                 if (pthread_join(p->pthread, NULL))
  93                         die("unable to join threaded lstat");
  94         }
  95 }
  96 #endif
  97
  98 int read_index_preload(struct index_state *index, const char **pathspec)
  99 {
 100         int retval = read_index(index);
 101
 102         preload_index(index, pathspec);
 103         return retval;
 104 }