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Heavy Performance degradation on linux

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  • rmsanjiv
    Hi! When I build antlr with -fPIC options and create a shared library for my application and use that to parse expressions then there is tremendous slow down
    Message 1 of 4 , Dec 15, 2004
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      Hi!

      When I build antlr with -fPIC options and create a shared library for
      my application and use that to parse expressions then there is
      tremendous slow down ONLY on linux. It runs around 200X faster on sun
      machines. Is there any known issue in that regard.

      It would be of tremendous help if someone can tell me the cause or
      share the similar experience.

      Regards,
      Sanjiv
    • Ric Klaren
      ... This sounds like a linux kernel or a compiler problem, some more specs could be helpfull. I would recommend building statically if speed is an issue. It
      Message 2 of 4 , Dec 15, 2004
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        On Wed, 15 Dec 2004 22:42:25 -0000, rmsanjiv <rmsanjiv@...> wrote:
        > When I build antlr with -fPIC options and create a shared library for
        > my application and use that to parse expressions then there is
        > tremendous slow down ONLY on linux. It runs around 200X faster on sun
        > machines. Is there any known issue in that regard.

        This sounds like a linux kernel or a compiler problem, some more specs
        could be helpfull. I would recommend building statically if speed is
        an issue. It would be interesting to see the speed difference on linux
        between a shared and statically linked lib (for reference)

        Cheers,

        Ric
      • rmsanjiv
        ... Hi Ric, Statically linked library runs pretty fast similar to shared library on solaris. I wonder why this issue is specific to only shared library on
        Message 3 of 4 , Dec 15, 2004
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          --- In antlr-interest@yahoogroups.com, Ric Klaren <ric.klaren@g...> wrote:
          > On Wed, 15 Dec 2004 22:42:25 -0000, rmsanjiv <rmsanjiv@h...> wrote:
          > > When I build antlr with -fPIC options and create a shared library for
          > > my application and use that to parse expressions then there is
          > > tremendous slow down ONLY on linux. It runs around 200X faster on sun
          > > machines. Is there any known issue in that regard.
          >
          > This sounds like a linux kernel or a compiler problem, some more specs
          > could be helpfull. I would recommend building statically if speed is
          > an issue. It would be interesting to see the speed difference on linux
          > between a shared and statically linked lib (for reference)
          >
          > Cheers,
          >
          > Ric

          Hi Ric,

          Statically linked library runs pretty fast similar to shared library
          on solaris. I wonder why this issue is specific to only shared library
          on linux. Any clue?

          Regards,
          Sanjiv
        • Ric Klaren
          ... First there s the issue that for -fPIC usually a number of restrictions are put on the generated code to make it relocatable. For some architectures this
          Message 4 of 4 , Dec 16, 2004
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            On Thu, 16 Dec 2004 00:05:09 -0000, rmsanjiv <rmsanjiv@...> wrote:
            > Statically linked library runs pretty fast similar to shared library
            > on solaris. I wonder why this issue is specific to only shared library
            > on linux. Any clue?

            First there's the issue that for -fPIC usually a number of
            restrictions are put on the generated code to make it relocatable. For
            some architectures this is good, for some others it is bad. It could
            also be due to some custom patches on the kernel you use (SELinux
            maybe?) I'm personally not aware that these give a slowdown but I
            could suspect it.

            Without any more information on the compiler you use or the kernel I
            cannot say anything.

            Cheers,

            Ric
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