statistics for GC

[Dave Love]

[Sorry if this is a duplicate -- I've had trouble sending out over the
weekend.]

I'd like to include something like this to allow measuring the GC
component when timing code.  I can't think it's controversial unless
the names of the new variables aren't right.

I have benchmarking utilities that use it.  It's probably useful for
ELP too, but I haven't looked at using it there.

Index: alloc.c
===================================================================
RCS file: /cvsroot/emacs/emacs/src/alloc.c,v
retrieving revision 1.290
diff -u -p -c -r1.290 alloc.c
cvs server: conflicting specifications of output style
*** alloc.c     24 Jan 2003 12:24:13 -0000      1.290
--- alloc.c     26 Jan 2003 18:53:46 -0000
*************** Lisp_Object Qgc_cons_threshold, Qchar_ta
*** 256,261 ****
--- 256,264 ----
  
  Lisp_Object Vpost_gc_hook, Qpost_gc_hook;
  
+ Lisp_Object Vgc_elapsed;      /* accumulated elapsed time in GC  */
+ EMACS_INT gcs_done;           /* accumulated GCs  */
+ 
  static void mark_buffer P_ ((Lisp_Object));
  static void mark_kboards P_ ((void));
  static void gc_sweep P_ ((void));
*************** Garbage collection happens automatically
*** 4085,4090 ****
--- 4088,4096 ----
    int message_p;
    Lisp_Object total[8];
    int count = SPECPDL_INDEX ();
+   EMACS_TIME t1, t2, t3;
+ 
+   EMACS_GET_TIME (t1);
  
    /* Can't GC if pure storage overflowed because we can't determine
       if something is a pure object or not.  */
*************** Garbage collection happens automatically
*** 4370,4376 ****
        safe_run_hooks (Qpost_gc_hook);
        unbind_to (count, Qnil);
      }
!   
    return Flist (sizeof total / sizeof *total, total);
  }
  
--- 4376,4391 ----
        safe_run_hooks (Qpost_gc_hook);
        unbind_to (count, Qnil);
      }
! 
!   /* Accumulate statistics.  */
!   EMACS_GET_TIME (t2);
!   EMACS_SUB_TIME (t3, t2, t1);
!   if (FLOATP (Vgc_elapsed))
!     XSETFLOAT (Vgc_elapsed, make_float (XFLOAT_DATA (Vgc_elapsed) +
!                                       EMACS_SECS (t3) +
!                                       EMACS_USECS (t3) * 1.0e-6));
!   gcs_done++;
! 
    return Flist (sizeof total / sizeof *total, total);
  }
  
*************** init_alloc ()
*** 5525,5530 ****
--- 5540,5547 ----
    setjmp_tested_p = longjmps_done = 0;
  #endif
  #endif
+   Vgc_elapsed = make_float (0.0);
+   gcs_done = 0;
  }
  
  void
*************** which includes both saved text and other
*** 5613,5618 ****
--- 5630,5643 ----
  
    staticpro (&Qchar_table_extra_slots);
    Qchar_table_extra_slots = intern ("char-table-extra-slots");
+ 
+   DEFVAR_LISP ("gc-elapsed", &Vgc_elapsed,
+              doc: /* Accumulated time elapsed in garbage collections.
+ The time is in seconds as a floating point value.
+ Programs may reset this to get statistics in a specific period.  */);
+   DEFVAR_INT ("gcs-done", &gcs_done,
+             doc: /* Accumulated number of garbage collections done.
+ Programs may reset this to get statistics in a specific period.  */);
  
    defsubr (&Scons);
    defsubr (&Slist);