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From "Henrik Stahl" <hst...@bea.com>
Subject RE: [DRLVM] 64-bit support with compressed pointer
Date Fri, 02 Feb 2007 08:13:22 GMT

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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