------- Comment #14 from jvdelisle at gcc dot gnu dot org 2007-12-01 04:22
-------
This is embarrassing and good at the same time:
Index: unix.c
===================================================================
--- unix.c (revision 130547)
+++ unix.c (working copy)
@@ -669,11 +669,8 @@ fd_seek (unix_stream * s, gfc_offset off
if (s->file_length == -1)
return SUCCESS;
- if (s->physical_offset == offset) /* Are we lucky and avoid syscall? */
- {
- s->logical_offset = offset;
- return SUCCESS;
- }
+ if (s->logical_offset == offset) /* Are we lucky and avoid syscall? */
+ return SUCCESS;
if (lseek (s->fd, offset, SEEK_SET) >= 0)
{
According to the comment we have been unlucky for a long time. :) With this
simple change alone, my sequential read benchmark goes from 23 seconds to .5
seconds. There is a regression in backspace_6.f90 which implies we need to fix
back space and leave the above fix in place if possible. The read test I am
using is reading a 36 megabyte unformatted file with ACCESS="stream". This is
impressive!
My write test with same file goes from about 6 seconds to about .5 seconds as
well.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33985
