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From "Weldon Washburn" <weldon...@gmail.com>
Subject Re: question about support for compressed StringBuffers
Date Fri, 22 Sep 2006 15:33:22 GMT
On 9/22/06, Craig Zilles <zilles@cs.uiuc.edu> wrote:
>
>
>        Okay, I'm going to be playing around with this code and other
> approaches for "[C" compression.
>
> Weldon -
>
>        you say:
>
> > historically things like string compression make a difference to
> > heap footprint and cache miss performance
>
>        do you know of other VMs that do this optimizations and if so if
> there is any public documentation?


Actually, I intentionally do not know about other VM implementations.  Its a
clean room thing.  In the past, I worked on ORP which morphed into DRLVM.  I
do remember some experiments on compressing [C.  From what I recall, it had
benefit.  The unused code you see in the source base is probably from these
experiments.



> - Craig
>
>
> On Sep 22, 2006, at 7:32 AM, Weldon Washburn wrote:
> > hmm... I tried to putting a standard  title on this email.  It
> > looks like we
> > all suffer from too much email.  So I repeat what I said earlier.
> >
> > All,
> > I took a look at this code.  I vote for keeping it.  The reason is
> > because
> > Java is string intensive and historically things like string
> > compression
> > make a difference to heap footprint and cache miss performance.
> > It looks
> > like a significant amount of work has already been put in this code.
> >
> > Craig,
> > It would be great if you can work on this code and get it going.  I
> > would be
> > happy to work with you to get the mods committed to Harmony svn.
> >
> >
> >
> >
> >
> > On 9/22/06, Alexey Varlamov <alexey.v.varlamov@gmail.com> wrote:
> >>
> >> Just a thought:
> >> DRLVM yet does not support 4-byte supplement characters of UTF8
> >> (6-bytes encoded in classfiles v49) - and this code may appear useful
> >> if/when we are going to fix that...
> >> --
> >> Alexey
> >>
> >> 2006/9/21, Geir Magnusson Jr. <geir@pobox.com>:
> >> > So do we fix it or scrap it?
> >> >
> >> > geir
> >> >
> >> > On Sep 20, 2006, at 10:23 AM, Ivan Volosyuk wrote:
> >> >
> >> > > This is an old code and it is unused for quite some time. Most
> >> likely
> >> > > it is broken.
> >> > > --
> >> > > Ivan
> >> > >
> >> > > On 9/20/06, Craig Zilles <zilles@cs.uiuc.edu> wrote:
> >> > >>
> >> > >>         I noticed in the file trunk/vm/vmcore/src/util/
> >> > >> vm_strings.cpp there
> >> > >> is some code to support the storage of strings in arrays of (8b)
> >> > >> bytes rather than arrays of (16b) unsigned shorts.  In the
> >> debugger,
> >> > >> I placed breakpoints in this code, and it was never active in
> >> my run.
> >> > >>
> >> > >>         Can someone tell me the current status of this code and,
> >> > >> if it is
> >> > >> active, how I can turn it on?  (From inspecting the source,
> >> it looked
> >> > >> inactive via hardcoding "false" on whether to compress the
> >> strings).
> >> > >> I might be interested in working on this code.
> >> > >
> >> > >
> >> ---------------------------------------------------------------------
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> >> >
> >> >
> >> >
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> >>
> >
> >
> > --
> > Weldon Washburn
> > Intel Middleware Products Division
>
>
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>


-- 
Weldon Washburn
Intel Middleware Products Division

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