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From "Xiao-Feng Li" <xiaofeng...@gmail.com>
Subject Re: [DRLVM] 64-bit support with compressed pointer
Date Fri, 02 Feb 2007 08:55:04 GMT
Henrik, thanks for the link. I knew you guys got great number with
compressed refs.

I assume the figure 2 in that page shows performance of same
configurations except for the processor bits. Probably the real power
of 64bit is with large heap size.

Henrik, does JRockit turn on the compressed pointer by default in
64bit platform? (if it's not confidential). Thanks,

-xiaofeng

On 2/2/07, Henrik Stahl <hstahl@bea.com> wrote:
>
> We have this in 64-bit versions of BEA JRockit. See here for one
> performance proof point:
> http://e-docs.bea.com/jrockit/releases/5026x/relnotes/relnotes.html#wp10
> 79760
>
> I guess the 13% number is close to the mark. It is app dependent,
> though.
>
> -- Henrik
>
> > -----Original Message-----
> > From: Aleksey Ignatenko [mailto:aleksey.ignatenko@gmail.com]
> > Sent: Friday, February 02, 2007 9:08 AM
> > To: dev@harmony.apache.org
> > Subject: Re: [DRLVM] 64-bit support with compressed pointer
> >
> > I suppose there is no easy way to do that, but one can scan
> > all places where
> >
> > #ifdef _EM64T_ appears and change appropriate places to
> > something like #ifdef _COMPRESSED_MODE. Plus scan such places
> > like gc_types.h in gc_cc, there is object header:
> >     VT32 vt_raw;
> >     unsigned info;
> > You need to have VT64 vt_raw;  for 64 bit mode.
> >
> > p.s. In some of discussions I read that compressed mode
> > (comparing to uncompressed one) improved performance on about
> > 13% on em64t.
> >
> > On 2/2/07, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> >
> > > Yes, that's exactly my question. I couldn't find an easy
> > way to turn
> > > off this compressed-ptr optimization. It's a little bit
> > surprising me.
> > > :-)
> > >
> > > Thanks,
> > > xiaofeng
> > >
> > > On 2/2/07, Aleksey Ignatenko <aleksey.ignatenko@gmail.com> wrote:
> > > > Did you check that it works on 64 bit mode with
> > uncomressed references.
> > > > I remember some time ago there were issues like hard coded
> > > > compressed references used in JIT (or probably somewhere
> > else) in 64bit mode.
> > > >
> > > > Best regards,
> > > > Aleksey.
> > > >
> > > > On 2/2/07, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> > > > >
> > > > > Hi, current 64bit support uses compressed reference pointer by
> > > > > default, i.e., a 64bit reference is stored as a 32bit
> > value plus a
> > > > > (global) base address. This can reduce the footprint of working
> > > > > set and at the same time improve cache locality. But
> > this has max
> > > > > heap size limitation.
> > > > >
> > > > > I wonder why not use non-compressed pointer as by
> > default, and the
> > > > > compressed pointer is only an optimization that can be applied
> > > > > when desirable. Comments?
> > > > >
> > > > > Thanks,
> > > > > xiaofeng
> > > > >
> > > >
> > > >
> > >
> >
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