OpenCL - why are there any pointers at all?

Article: Introduction to OpenCL
By: Richard Cownie (tich.delete@this.pobox.com), December 18, 2010 2:39 pm
Room: Moderated Discussions
BorisG (borisgin@yahoo.com) on 12/18/10 wrote:
---------------------------
>The major issue, which heavily limits application of OpenCL(GPGPU), is inability
>to share virtual memory (pointers) between CPU and GPU. The second one is lack of
>malloc (and system call in general) on GPU.

malloc() isn't a system call. It's a normal procedure call
(usually, but not necessarily, to a shared library).
If it were a system call, it would be painfully slow for
allocating tens of millions of small blocks.

Typically malloc grabs memory from the OS in relatively
large chunks, using either sbrk() or mmap(). But it doesn't
pay the overhead of a system call on each malloc() call -
that would be a disaster.

I've used other systems (networks of transputers, with no
shared memory) where system services have to accessed by
passing messages to some other machine that has the IO
capability, rather than just by doing a system call.
It's certainly a pain in the ass, but not necessarily a
showstopper, depending on the compute/IO ratio of your
problem.

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TopicPosted ByDate
OpenCL article onlineDavid Kanter2010/12/09 02:44 AM
  OpenCL article onlineXN2010/12/09 06:33 AM
    OpenCL article onlineDavid Kanter2010/12/09 01:54 PM
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    OpenCL article onlineDavid Kanter2010/12/09 02:38 PM
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  Performance portabilityBryan Catanzaro2010/12/10 12:43 PM
    Performance portabilityltcommander.data2010/12/10 07:11 PM
      It is difficult to runtime optimize away the difference between a CPU and GPUMark Roulo2010/12/10 07:50 PM
        It is difficult to runtime optimize away the difference between a CPU and GPUhobold2010/12/11 03:35 AM
          It is difficult to runtime optimize away the difference between a CPU and GPUMark Roulo2010/12/12 01:20 PM
            It is difficult to runtime optimize away the difference between a CPU and GPUhobold2010/12/12 03:31 PM
              It is difficult to runtime optimize away the difference between a CPU and GPUanon2010/12/12 04:24 PM
                It is difficult to runtime optimize away the difference between a CPU and GPUhobold2010/12/13 03:44 AM
        Specially when the language provides almost no hardware abstraction (NT)EduardoS2010/12/11 10:53 AM
    Performance portabilityWainwright2010/12/11 03:44 PM
      Performance portabilityEduardoS2010/12/11 03:57 PM
        Performance portabilityWainwright2010/12/11 04:02 PM
          Performance portabilityEduardoS2010/12/11 08:20 PM
            Performance portabilityWainwright2010/12/12 02:22 AM
      Performance portabilityDavid Kanter2010/12/11 05:53 PM
        Performance portabilityEduardoS2010/12/11 08:23 PM
          Performance portabilityDavid Kanter2010/12/11 09:06 PM
            Performance portabilityWainwright2010/12/12 02:26 AM
            Performance portabilityEduardoS2010/12/12 09:04 AM
  OpenCL article onlineAlan Commike2010/12/14 01:01 PM
  OpenCL - why are there any pointers at all?Rob Thorpe2010/12/16 03:45 AM
    OpenCL - why are there any pointers at all?EduardoS2010/12/16 01:51 PM
      OpenCL - why are there any pointers at all?Rob Thorpe2010/12/17 03:19 AM
        OpenCL - why are there any pointers at all?Richard Cownie2010/12/17 07:02 AM
          OpenCL - why are there any pointers at all?Rob Thorpe2010/12/17 08:29 AM
            OpenCL - why are there any pointers at all?Richard Cownie2010/12/17 09:13 AM
              OpenCL - why are there any pointers at all?Rob Thorpe2010/12/17 10:03 AM
                OpenCL - why are there any pointers at all?Richard Cownie2010/12/17 10:53 AM
                  OpenCL - why are there any pointers at all?Rob Thorpe2010/12/17 11:19 AM
                    OpenCL - why are there any pointers at all?Richard Cownie2010/12/17 11:51 AM
                OpenCL - why are there any pointers at all?hobold2010/12/17 11:06 AM
          OpenCL - why are there any pointers at all?EduardoS2010/12/18 07:58 AM
            OpenCL - why are there any pointers at all?anon2010/12/18 10:27 AM
            OpenCL - why are there any pointers at all?BorisG2010/12/18 10:33 AM
              OpenCL - why are there any pointers at all?Richard Cownie2010/12/18 02:39 PM
  OpenCL article onlineEmil Briggs2010/12/19 06:40 AM
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