preload-index.c

   1 /*
   2  * Copyright (C) 2008 Linus Torvalds
   3  */
   4 #include "cache.h"
   5 #include <pthread.h>
   6
   7 /*
   8  * Mostly randomly chosen maximum thread counts: we
   9  * cap the parallelism to 20 threads, and we want
  10  * to have at least 500 lstat's per thread for it to
  11  * be worth starting a thread.
  12  */
  13 #define MAX_PARALLEL (20)
  14 #define THREAD_COST (500)
  15
  16 struct thread_data {
  17         pthread_t pthread;
  18         struct index_state *index;
  19         const char **pathspec;
  20         int offset, nr;
  21 };
  22
  23 static void *preload_thread(void *_data)
  24 {
  25         int nr;
  26         struct thread_data *p = _data;
  27         struct index_state *index = p->index;
  28         struct cache_entry **cep = index->cache + p->offset;
  29
  30         nr = p->nr;
  31         if (nr + p->offset > index->cache_nr)
  32                 nr = index->cache_nr - p->offset;
  33
  34         do {
  35                 struct cache_entry *ce = *cep++;
  36                 struct stat st;
  37
  38                 if (ce_stage(ce))
  39                         continue;
  40                 if (ce_uptodate(ce))
  41                         continue;
  42                 if (!ce_path_match(ce, p->pathspec))
  43                         continue;
  44                 if (lstat(ce->name, &st))
  45                         continue;
  46                 if (ie_match_stat(index, ce, &st, CE_MATCH_RACY_IS_DIRTY))
  47                         continue;
  48                 ce_mark_uptodate(ce);
  49         } while (--nr > 0);
  50         return NULL;
  51 }
  52
  53 static void preload_index(struct index_state *index, const char **pathspec)
  54 {
  55         int threads, i, work, offset;
  56         struct thread_data data[MAX_PARALLEL];
  57
  58         if (!core_preload_index)
  59                 return;
  60
  61         threads = index->cache_nr / THREAD_COST;
  62         if (threads < 2)
  63                 return;
  64         if (threads > MAX_PARALLEL)
  65                 threads = MAX_PARALLEL;
  66         offset = 0;
  67         work = (index->cache_nr + threads - 1) / threads;
  68         for (i = 0; i < threads; i++) {
  69                 struct thread_data *p = data+i;
  70                 p->index = index;
  71                 p->pathspec = pathspec;
  72                 p->offset = offset;
  73                 p->nr = work;
  74                 offset += work;
  75                 if (pthread_create(&p->pthread, NULL, preload_thread, p))
  76                         die("unable to create threaded lstat");
  77         }
  78         for (i = 0; i < threads; i++) {
  79                 struct thread_data *p = data+i;
  80                 if (pthread_join(p->pthread, NULL))
  81                         die("unable to join threaded lstat");
  82         }
  83 }
  84
  85 int read_index_preload(struct index_state *index, const char **pathspec)
  86 {
  87         int retval = read_index(index);
  88
  89         preload_index(index, pathspec);
  90         return retval;
  91 }