a code reduction function addition to cam_xpt

[Brooks Davis]

On Mon, Nov 20, 2006 at 11:18:43PM +0100, Attilio Rao wrote:
> 2006/11/20, Brooks Davis <brooks at one-eyed-alien.net>:
> >On Mon, Nov 20, 2006 at 01:31:01AM +0100, Attilio Rao wrote:
> >> 2006/11/20, mjacob at freebsd.org <mjacob at freebsd.org>:
> >> >There are *far* too many:
> >> >
> >> >        xpt_print_path(path);
> >> >        printf("foo\n");
> >> >
> >> >constructs. How about we just join them?
> >> >
> >> >==== //depot/projects/newisp/cam/cam_xpt.c#12 -
> >> >/home/FreeBSD/p4/newisp/cam/cam_xpt.c ====
> >> >@@ -63,6 +63,7 @@
> >> >  #include <cam/scsi/scsi_all.h>
> >> >  #include <cam/scsi/scsi_message.h>
> >> >  #include <cam/scsi/scsi_pass.h>
> >> >+#include <machine/stdarg.h>    /* for xpt_print below */
> >> >  #include "opt_cam.h"
> >> >
> >> >  /* Datastructures internal to the xpt layer */
> >> >@@ -4160,6 +4161,16 @@
> >> >        }
> >> >  }
> >> >
> >> >+void
> >> >+xpt_print(struct cam_path *path, const char *fmt, ...)
> >> >+{
> >> >+       va_list ap;
> >> >+       xpt_print_path(path);
> >> >+       va_start(ap, fmt);
> >> >+       vprintf(fmt, ap);
> >> >+       va_end(ap);
> >> >+}
> >> >+
> >> >==== //depot/projects/newisp/cam/cam_xpt.h#1 -
> >> >/home/FreeBSD/p4/newisp/cam/cam_xpt.h ====
> >> >@@ -62,6 +62,7 @@
> >> >  int                   xpt_path_comp(struct cam_path *path1,
> >> >                                      struct cam_path *path2);
> >> >  void                  xpt_print_path(struct cam_path *path);
> >> >+void                   xpt_print(struct cam_path *path, const char 
> >*fmt,
> >> >...);
> >> >  int                   xpt_path_string(struct cam_path *path, char 
> >*str,
> >> >                                        size_t str_len);
> >> >  path_id_t             xpt_path_path_id(struct cam_path *path);
> >>
> >> Would not be better a preprocessing stub?
> >>
> >> something like:
> >>
> >> #define XPT_PRINT(path, fmt, ...) do {
> >>            \
> >>              xpt_print_path(path);
> >>                      \
> >>              printf(fmt, __VA_ARGS__);
> >>                  \
> >> } while (0)
> >
> >Why?  What is gained?  FWIW, when I added if_printif it reduced kernel
> >size by several KB.  If there's a similar effect here we should take
> >advantage of it.
> 
> It is simply faster (one function calling less), even if probabilly
> this could be mitigated with -fomit-frame-pointer (IMHO, this is not
> as over used as if_printf...).

There's not possibly way you could measure a meaningful difference in
performance except in a case where the system was unusable because it
spent all its time blocked waiting for the console to update.

-- Brooks
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