77 * Portions Copyright (c) 1994, Regents of the University of California
88 *
99 * IDENTIFICATION
10- * $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.118 2005/07/04 04:51:48 tgl Exp $
10+ * $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.119 2005/08/07 18:47:19 tgl Exp $
1111 *
1212 * NOTES:
1313 *
@@ -300,10 +300,16 @@ pg_fdatasync(int fd)
300300 * count_usable_fds --- count how many FDs the system will let us open,
301301 *and estimate how many are already open.
302302 *
303+ * We stop counting if usable_fds reaches max_to_probe. Note: a small
304+ * value of max_to_probe might result in an underestimate of already_open;
305+ * we must fill in any "gaps" in the set of used FDs before the calculation
306+ * of already_open will give the right answer. In practice, max_to_probe
307+ * of a couple of dozen should be enough to ensure good results.
308+ *
303309 * We assume stdin (FD 0) is available for dup'ing
304310 */
305311static void
306- count_usable_fds (int * usable_fds ,int * already_open )
312+ count_usable_fds (int max_to_probe , int * usable_fds ,int * already_open )
307313{
308314int * fd ;
309315int size ;
@@ -314,7 +320,7 @@ count_usable_fds(int *usable_fds, int *already_open)
314320size = 1024 ;
315321fd = (int * )palloc (size * sizeof (int ));
316322
317- /* dup until failure... */
323+ /* dup until failureor probe limit reached */
318324for (;;)
319325{
320326int thisfd ;
@@ -337,6 +343,9 @@ count_usable_fds(int *usable_fds, int *already_open)
337343
338344if (highestfd < thisfd )
339345highestfd = thisfd ;
346+
347+ if (used >=max_to_probe )
348+ break ;
340349}
341350
342351/* release the files we opened */
@@ -364,14 +373,16 @@ set_max_safe_fds(void)
364373int usable_fds ;
365374int already_open ;
366375
367- /*
368- * We want to set max_safe_fds to MIN(usable_fds,
369- * max_files_per_process - already_open) less the slop factor for
370- * files that are opened without consulting fd.c. This ensures that
371- * we won't exceed either max_files_per_process or the
372- * experimentally-determined EMFILE limit.
376+ /*----------
377+ * We want to set max_safe_fds to
378+ *MIN(usable_fds, max_files_per_process - already_open)
379+ * less the slop factor for files that are opened without consulting
380+ * fd.c. This ensures that we won't exceed either max_files_per_process
381+ * or the experimentally-determined EMFILE limit.
382+ *----------
373383 */
374- count_usable_fds (& usable_fds ,& already_open );
384+ count_usable_fds (max_files_per_process ,
385+ & usable_fds ,& already_open );
375386
376387max_safe_fds = Min (usable_fds ,max_files_per_process - already_open );
377388