Re: Forth dictionary implementation and performance

From	Paul Rubin <no.email@nospam.invalid>
Newsgroups	comp.lang.forth
Subject	Re: Forth dictionary implementation and performance
Date	2016-02-01 00:47 -0800
Organization	A noiseless patient Spider
Message-ID	<87twlsq0ks.fsf@jester.gateway.pace.com> (permalink)
References	<2016Jan29.184253@mips.complang.tuwien.ac.at> <87k2mrrk95.fsf@jester.gateway.pace.com> <2016Jan30.145442@mips.complang.tuwien.ac.at> <8737tdr075.fsf@jester.gateway.pace.com> <2016Feb1.074719@mips.complang.tuwien.ac.at>

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anton@mips.complang.tuwien.ac.at (Anton Ertl) writes:
> <http://pubs.opengroup.org/onlinepubs/9699919799/functions/mmap.html>:
> |If PROT_WRITE is specified, the application shall ensure that it has
> |opened the file descriptor fildes with write permission unless
> |MAP_PRIVATE is specified in the flags parameter as described below.

Ah, ok, that clears things up nicely, thanks.

> My expectation is that read first causes the disk contents to be
> loaded into kernel buffers, and then copies the data to user space,
> while mmap() maps the OS buffers into user space without copying
> (except the copy-on-write when I write to it).

That's possible, though read() might be optimized in the case that the
user buffer is page aligned.  The copying might still be slower than the
extra context switches and potentially extra disk operations.

Thread

Forth dictionary implementation and performance anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-29 17:42 +0000
  Re: Forth dictionary implementation and performance Paul Rubin <no.email@nospam.invalid> - 2016-01-29 16:20 -0800
    Re: Forth dictionary implementation and performance anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-30 13:54 +0000
      Re: Forth dictionary implementation and performance Paul Rubin <no.email@nospam.invalid> - 2016-01-31 11:57 -0800
        Re: Forth dictionary implementation and performance anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-02-01 06:47 +0000
          Re: Forth dictionary implementation and performance Paul Rubin <no.email@nospam.invalid> - 2016-02-01 00:47 -0800
            Re: Forth dictionary implementation and performance anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-02-01 11:13 +0000
  Re: Forth dictionary implementation and performance Bernd Paysan <bernd.paysan@gmx.de> - 2016-01-30 01:57 +0100
    Re: Forth dictionary implementation and performance anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-30 17:18 +0000
      Re: Forth dictionary implementation and performance anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-30 17:51 +0000
  Re: Forth dictionary implementation and performance Paul Rubin <no.email@nospam.invalid> - 2016-01-29 18:01 -0800
    Re: Forth dictionary implementation and performance anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-30 13:59 +0000
      Re: Forth dictionary implementation and performance anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-01-30 17:38 +0000
        Re: Forth dictionary implementation and performance Paul Rubin <no.email@nospam.invalid> - 2016-01-31 12:05 -0800
          Re: Forth dictionary implementation and performance Albert van der Horst <albert@spenarnc.xs4all.nl> - 2016-02-01 03:01 +0000
          Re: Forth dictionary implementation and performance anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-02-01 06:17 +0000
            Re: Forth dictionary implementation and performance "Elizabeth D. Rather" <erather@forth.com> - 2016-01-31 21:27 -1000
  Re: Forth dictionary implementation and performance hughaguilar96@gmail.com - 2016-01-30 15:42 -0800

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