Re: PATCH: java: suppress java.lang.Object constructor

[Jeff Sturm <jsturm at one-point dot com>]

On 18 Jul 2001, Tom Tromey wrote:
> Jeff> I see a disproportionate number of cache misses in
> Jeff> _Jv_AllocObject, ostensibly due to the finalizer check
> Jeff> (java.lang.Object's vtable is seldom used otherwise).
> 
> That's interesting.  How do you measure cache misses?

With hardware event counters on the Alpha CPU, and a user-mode tool
called iprobe.  Below is a sample report for dcache accesses/misses on
GCBench.

Only the top 6 functions are reported.  Note that _Jv_AllocObject
single-handedly generates more dcache traffic than the entire gcbench
image.  The other results seem normal.

Jeff


+----------------------------------------+
| Profile Report | Event = Dcache Access |
+----------------------------------------+

    * One sample = 65536 events *

                                          Sample Image Total
Name                                       Count   Pct   Pct
----                                       -----   ---   ---
/home/jsturm/Boehm/gcbench                  4385        19.2
  _ZN7GCBench8PopulateEiP4Node              2224  50.7   9.7
  _ZN7GCBench8MakeTreeEi                    2133  48.6   9.3
/opt/gcc/lib/libgcjgc.so.1.0.1             11534        50.5
  GC_allochblk_nth                          1094   9.5   4.8
  GC_gcj_malloc                             6663  57.8  29.2
  GC_mark_from                              2403  20.8  10.5
/opt/gcc/lib/libgcj.so.2.0.0                4807        21.0
  _Jv_AllocObject                           4777  99.4  20.9

+--------------------------------------+
| Profile Report | Event = Dcache Miss |
+--------------------------------------+

    * One sample = 16384 events *

                                          Sample Image Total
Name                                       Count   Pct   Pct
----                                       -----   ---   ---
/home/jsturm/Boehm/gcbench                   607        13.3
  _ZN7GCBench8PopulateEiP4Node               376  61.9   8.2
  _ZN7GCBench8MakeTreeEi                     225  37.1   4.9
/opt/gcc/lib/libgcjgc.so.1.0.1              3336        73.1
  GC_allochblk_nth                           164   4.9   3.6
  GC_gcj_malloc                             1722  51.6  37.7
  GC_mark_from                               910  27.3  19.9
/opt/gcc/lib/libgcj.so.2.0.0                 401         8.8
  _Jv_AllocObject                            398  99.3   8.7