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
  38         nr = p->nr;
  39         if (nr + p->offset > index->cache_nr)
  40                 nr = index->cache_nr - p->offset;
  41
  42         do {
  43                 struct cache_entry *ce = *cep++;
  44                 struct stat st;
  45
  46                 if (ce_stage(ce))
  47                         continue;
  48                 if (ce_uptodate(ce))
  49                         continue;
  50                 if (!ce_path_match(ce, p->pathspec))
  51                         continue;
  52                 if (lstat(ce->name, &st))
  53                         continue;
  54                 if (ie_match_stat(index, ce, &st, CE_MATCH_RACY_IS_DIRTY))
  55                         continue;
  56                 ce_mark_uptodate(ce);
  57         } while (--nr > 0);
  58         return NULL;
  59 }
  60
  61 static void preload_index(struct index_state *index, const char **pathspec)
  62 {
  63         int threads, i, work, offset;
  64         struct thread_data data[MAX_PARALLEL];
  65
  66         if (!core_preload_index)
  67                 return;
  68
  69         threads = index->cache_nr / THREAD_COST;
  70         if (threads < 2)
  71                 return;
  72         if (threads > MAX_PARALLEL)
  73                 threads = MAX_PARALLEL;
  74         offset = 0;
  75         work = (index->cache_nr + threads - 1) / threads;
  76         for (i = 0; i < threads; i++) {
  77                 struct thread_data *p = data+i;
  78                 p->index = index;
  79                 p->pathspec = pathspec;
  80                 p->offset = offset;
  81                 p->nr = work;
  82                 offset += work;
  83                 if (pthread_create(&p->pthread, NULL, preload_thread, p))
  84                         die("unable to create threaded lstat");
  85         }
  86         for (i = 0; i < threads; i++) {
  87                 struct thread_data *p = data+i;
  88                 if (pthread_join(p->pthread, NULL))
  89                         die("unable to join threaded lstat");
  90         }
  91 }
  92 #endif
  93
  94 int read_index_preload(struct index_state *index, const char **pathspec)
  95 {
  96         int retval = read_index(index);
  97
  98         preload_index(index, pathspec);
  99         return retval;
 100 }