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From "Henrik Stahl" <hst...@bea.com>
Subject RE: [DRLVM] 64-bit support with compressed pointer
Date Fri, 02 Feb 2007 08:59:34 GMT

http://e-docs.bea.com/jrockit/jrdocs/refman/optionXX.html#wp1021022

Though the docs are misleading, it is only enabled by default if -Xmx is
4 gb or less. I'll have this fixed.

-- Henrik

> -----Original Message-----
> From: Xiao-Feng Li [mailto:xiaofeng.li@gmail.com] 
> Sent: Friday, February 02, 2007 9:55 AM
> To: dev@harmony.apache.org
> Subject: Re: [DRLVM] 64-bit support with compressed pointer
> 
> 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#wp
> > 10
> > 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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