On 12/6/06, Weldon Washburn <[EMAIL PROTECTED]> wrote:
On 12/5/06, Mikhail Fursov <[EMAIL PROTECTED]> wrote:
>
> Xiao-Feng,
> I have finished all inlining tasks planned for this week and now can start
> WB inlining task.
> I'm going to use your patch with allocation helper as basis (
> http://issues.apache.org/jira/browse/HARMONY-2398), and I will be able to
> post my patch (get the diff) only after H2398 is applied.
>
I hope I'll WB in a day or two. The only thing I need to know: what is the
state of gc_gen? Which specs does it run? What can I use to test stability
and performance of my changes?
Mikhail, thanks. GCv5 can run the SPEC benchmarks without problem. So
I guess SPECJBB2005 is good enough for your code test in both
performance and stability. I will work with you closely for any
support you may need. Well my observation is you are smart enough to
deal with it. ;-) (There are a couple of configurations for GCv5 for
performance tuning, but I guess the default setting can already
exhibit the performance improvement.)
I just committed 2398. Let me know when you have the WB patch ready and I
will try to commit it.
Thanks, Weldon.
On 12/5/06, Ivan Volosyuk <[EMAIL PROTECTED]> wrote:
> >
> > On 12/5/06, Xiao-Feng Li <[EMAIL PROTECTED]> wrote:
> > > On 12/4/06, Robin Garner <[EMAIL PROTECTED]> wrote:
> > > > > On 11/30/06, Robin Garner <[EMAIL PROTECTED]> wrote:
> > > > >> Xiao-Feng Li wrote:
> > > > >> >
> > > > >> > /* If the slot is in NOS or the target is not in NOS, we
> > simply
> > > > >> > return*/
> > > > >> > if( p_slot.GE( NOS_BOUNDARY) || p_target.LT(
> NOS_BOUNDARY)
> > )
> > > > >> > return;
> > > > >> >
> > > > >> > /* Otherwise, we need remember it in native code. */
> > > > >> > VMHelper.WriteBarrierSlotRem(p_slot, p_target);
> > > > >>
> > > > >> Shouldn't this be
> > > > >> if( p_slot.LT( NOS_BOUNDARY) && p_target.GE(
> NOS_BOUNDARY)
> > )
> > > > >> VMHelper.WriteBarrierSlotRem(p_slot, p_target);
> > > > >>
> > > > >> ?? Ie we're recording old-to-new pointers.
> > > > >
> > > > > Robin, aren't they the same but exchanging the two branches of
> > > > > condition checking? :-)
> > > >
> > > > Yes, of course. Doh. !(A|B) = !A&!B.
> > > >
> > > > I do think the second is clearer though :)
> > >
> > > Since I somehow am not a branch predictor fun, I am used to put the
> > > common TRUE case in the branch condition so that the fast path can be
> > > scheduled as fall-through branch automatically by the JIT. This might
> > > be very old and obsolete C programming wisdom. :-)
> >
Actually, in modern compilers this may not work. I like approach used
in linux kernel:
if (unlikely(expr)) {
}
where 'unlikely' is highly compiler specific and defined something like:
#define likely(x) __builtin_expect(!!(x), 1)
#define unlikely(x) __builtin_expect(!!(x), 0)
Ivan, yes, that is the only way that really works without profiling
support. Some processors also take the hint from compiler for branch
prediction.
Thanks,
xiaofeng
> > --
> > Ivan
> >
>
>
>
> --
> Mikhail Fursov
>
>
--
Weldon Washburn
Intel Enterprise Solutions Software Division
