Re: Forth dictionary implementation and performance

From	anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups	comp.lang.forth
Subject	Re: Forth dictionary implementation and performance
Date	2016-02-01 11:13 +0000
Organization	Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID	<2016Feb1.121340@mips.complang.tuwien.ac.at> (permalink)
References	(1 earlier) <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> <87twlsq0ks.fsf@jester.gateway.pace.com>

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Paul Rubin <no.email@nospam.invalid> writes:
>anton@mips.complang.tuwien.ac.at (Anton Ertl) writes:
>> 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.

What kind of optimization do you have in mind?

>The copying might still be slower than the
>extra context switches and potentially extra disk operations.

It's also possible to optimize mmap() to avoid context switches in
many by mapping the buffers that are already in memory and contain the
file data when mmap() is called into the user space eagerly instead of
demand-paging these pages into user space.  I have no idea if that is
done, however.

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
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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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