[gthumb-list] [PATCH][RFC] Reduce cpu usage wit h many images in one directory

[Ibragimov Rinat <ibragimovrinat mail ru>]

Hello.

 I'm using GThumb as image viewer and it's a great app, but it is slow when number of
 images becomes very large. My typical workload -- more than 3000 images in one folder.
 When I open such folder, GThumb consumes 100% cpu for quite a long time. 
 I digged a bit and found that it actually has quadratic complexity. _gth_file_list_update_next_thumb function
 tries to create thumbnails for almost all images (N_CREATEAHEAD macro evaluates to 50000)
 and is called for _every_ image. I understand that patch below is a dirty hack, but when I measured
 user time on 20000-images-testcase it showed cpu time usage reduction from 10.5 minutes to
 10 seconds.

 diff --git a/gthumb/gth-file-list.c b/gthumb/gth-file-list.c
 index 3717273..5b4d5c9 100644
 --- a/gthumb/gth-file-list.c
 +++ b/gthumb/gth-file-list.c
 @@ -1525,7 +1525,6 @@ _gth_file_list_update_thumb (GthFileList *file_list,
                 }

                 if (job == NULL) {
 - file_list->priv->update_event = g_idle_add (restart_thumb_update_cb, file_list);
                         return;
                 }
         }


 There is another place with same problem. However it has lower performace effec (10sec -> 8sec)

 diff --git a/gthumb/gth-file-store.c b/gthumb/gth-file-store.c
 index ddb3075..29966c2 100644
 --- a/gthumb/gth-file-store.c
 +++ b/gthumb/gth-file-store.c
 @@ -779,6 +779,7 @@ _gth_file_store_update_visibility (GthFileStore *file_store,
   GthFileData *file;
   int j, k;
   gboolean row_deleted;
 + GHashTable *file_index;
  
  
  #ifdef DEBUG_FILE_STORE
 @@ -818,12 +819,14 @@ g_print ("UPDATE VISIBILITY\n");
   /* reorder and filter */
  
   _gth_file_store_sort (file_store, all_rows, all_rows_n);
 + file_index = g_hash_table_new (g_direct_hash, g_direct_equal);
  
   files = NULL;
   for (i = 0; i < all_rows_n; i++) {
   GthFileRow *row = all_rows[i];
  
   row->abs_pos = i;
 + g_hash_table_insert (file_index, row->file_data, GINT_TO_POINTER (i));
   files = g_list_prepend (files, g_object_ref (row->file_data));
   }
   files = g_list_reverse (files);
 @@ -831,21 +834,15 @@ g_print ("UPDATE VISIBILITY\n");
   new_rows_n = 0;
   gth_test_set_file_list (file_store->priv->filter, files);
   while ((file = gth_test_get_next (file_store->priv->filter)) != NULL) {
 - GthFileRow *row = NULL;
 -
 - for (i = 0; i < all_rows_n; i++) {
 - row = all_rows[i];
 - if (row->file_data == file)
 - break;
 - }
 -
 + i = GPOINTER_TO_INT (g_hash_table_lookup (file_index, file));
   g_assert (i < all_rows_n);
  
 - row->visible = TRUE;
 + all_rows[i]->visible = TRUE;
   new_rows_n++;
   }
  
   _g_object_list_unref (files);
 + g_hash_table_unref (file_index);
  
   /* create the new visible rows array */