Re: Memory management and custom allocator

From	Keith Thompson <kst-u@mib.org>
Newsgroups	comp.lang.c
Subject	Re: Memory management and custom allocator
Date	2012-01-02 13:42 -0800
Organization	None to speak of
Message-ID	<lnzke56at9.fsf@nuthaus.mib.org> (permalink)
References	(3 earlier) <jdpp3r$8h3$1@dont-email.me> <jdqjtf$bqd$1@reader1.panix.com> <jdsact$nr6$1@dont-email.me> <CTiMq.187959$WC5.163670@newsfe09.ams2> <jdsg2h$mkb$1@dont-email.me>

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Eric Sosman <esosman@ieee-dot-org.invalid> writes:
[...]
>> This is where you redesign your struct to use only 32 bytes, or find a
>> good use for another 20 bytes to make 64.
[...]
>> Such structs are easier to index in arrays.
>
>      Nonsense.  The `[]' operator works with equal ease on arrays
> of any element size at all.
[...]

It's certainly possible that `[]' on an array of 64-bytes elements
will be faster than `[]' on an array with 44-byte elements.
(It's also possible that it could have the same or even slower
performance.)

But padding a structure to make it 64 bytes for the purpose of making
array indexing faster is a classic case of micro-optimization, to
be attempted only if measurements show that it makes a significant
difference.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
    Will write code for food.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

Thread

[Slightly OT] Memory management and custom allocator FtM <fmassei@gmail.com> - 2011-12-31 06:56 -0800
  Re: [Slightly OT] Memory management and custom allocator Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-12-31 11:08 -0500
    Re: Memory management and custom allocator FtM <fmassei@gmail.com> - 2011-12-31 08:28 -0800
  Re: [Slightly OT] Memory management and custom allocator Johann Klammer <klammerr@NOSPAM.aon.at> - 2011-12-31 17:39 +0100
    Re: Memory management and custom allocator FtM <fmassei@gmail.com> - 2011-12-31 08:55 -0800
      Re: Memory management and custom allocator Johann Klammer <klammerr@NOSPAM.aon.at> - 2011-12-31 19:01 +0100
        Re: Memory management and custom allocator Kaz Kylheku <kaz@kylheku.com> - 2011-12-31 18:31 +0000
  Re: [Slightly OT] Memory management and custom allocator Kaz Kylheku <kaz@kylheku.com> - 2011-12-31 17:24 +0000
    Re: Memory management and custom allocator FtM <fmassei@gmail.com> - 2011-12-31 09:52 -0800
      Re: Memory management and custom allocator Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-12-31 14:30 -0500
      Re: Memory management and custom allocator Markus Wichmann <nullplan@gmx.net> - 2012-01-01 12:21 +0100
        Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-01 12:54 +0000
          Re: Memory management and custom allocator Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-01 09:03 -0500
            Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-01 16:23 +0000
            Re: Memory management and custom allocator jgk@panix.com (Joe keane) - 2012-01-01 21:41 +0000
              Re: Memory management and custom allocator Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-02 08:10 -0500
                Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-02 14:07 +0000
                Re: Memory management and custom allocator Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-02 09:47 -0500
                Re: Memory management and custom allocator FtM <fmassei@gmail.com> - 2012-01-02 08:36 -0800
                Re: Memory management and custom allocator Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-02 13:43 -0500
                Re: Memory management and custom allocator FtM <fmassei@gmail.com> - 2012-01-02 11:38 -0800
                Re: Memory management and custom allocator jgk@panix.com (Joe keane) - 2012-01-03 13:14 +0000
                Re: Memory management and custom allocator 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-03 06:07 -0800
                Re: Memory management and custom allocator 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-05 17:06 -0800
                Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-02 21:36 +0000
                Re: Memory management and custom allocator Kaz Kylheku <kaz@kylheku.com> - 2012-01-02 21:44 +0000
                Re: Memory management and custom allocator 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-02 23:10 -0800
                Re: Memory management and custom allocator Keith Thompson <kst-u@mib.org> - 2012-01-02 13:42 -0800
                Re: Memory management and custom allocator Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-02 17:38 -0500
                Re: Memory management and custom allocator jgk@panix.com (Joe keane) - 2012-01-02 21:45 +0000
                Re: Memory management and custom allocator Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-02 18:19 -0500
                Re: Memory management and custom allocator Keith Thompson <kst-u@mib.org> - 2012-01-02 15:42 -0800
                Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-02 23:59 +0000
                Re: Memory management and custom allocator Kleuske <kleuske@nowhere.net> - 2012-01-03 11:38 +0000
                Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-03 12:49 +0000
                Re: Memory management and custom allocator jgk@panix.com (Joe keane) - 2012-01-04 23:42 +0000
                Re: Memory management and custom allocator Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-04 20:23 -0500
                Re: Memory management and custom allocator Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-01-05 23:31 +0200
                Re: Memory management and custom allocator jgk@panix.com (Joe keane) - 2012-01-04 21:52 +0000
                Re: Memory management and custom allocator Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-04 20:31 -0500
                Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-05 01:45 +0000
                Re: Memory management and custom allocator Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-01-07 05:55 +0200
                Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-07 12:02 +0000
          Re: Memory management and custom allocator Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-01-01 09:08 -0500
            Re: Memory management and custom allocator FtM <fmassei@gmail.com> - 2012-01-01 10:08 -0800
              Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-01 23:34 +0000
                Re: Memory management and custom allocator FtM <fmassei@gmail.com> - 2012-01-02 02:18 -0800
                Re: Memory management and custom allocator 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-02 02:34 -0800
                Re: Memory management and custom allocator FtM <fmassei@gmail.com> - 2012-01-02 02:43 -0800
                Re: Memory management and custom allocator 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-02 03:11 -0800
                Re: Memory management and custom allocator FtM <fmassei@gmail.com> - 2012-01-02 08:17 -0800
                Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-02 11:40 +0000
                Re: Memory management and custom allocator FtM <fmassei@gmail.com> - 2012-01-02 08:27 -0800
          Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-01 23:26 +0000
            Re: Memory management and custom allocator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-01 23:54 +0000
              Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-02 00:32 +0000
          Re: Memory management and custom allocator Kaz Kylheku <kaz@kylheku.com> - 2012-01-02 02:46 +0000
            Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-02 11:53 +0000
              Re: Memory management and custom allocator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-02 15:18 +0000
          Re: Memory management and custom allocator jgk@panix.com (Joe keane) - 2012-01-03 12:21 +0000
          Re: Memory management and custom allocator Karl Malbrain <malbrain@yahoo.com> - 2012-01-04 16:48 -0800
            Re: Memory management and custom allocator "BartC" <bc@freeuk.com> - 2012-01-05 01:36 +0000
  Re: [Slightly OT] Memory management and custom allocator "io_x" <a@b.c.invalid> - 2012-01-01 17:02 +0100
  Re: [Slightly OT] Memory management and custom allocator jgk@panix.com (Joe keane) - 2012-01-01 21:21 +0000
  Re: [Slightly OT] Memory management and custom allocator 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-01 21:01 -0800
  Re: [Slightly OT] Memory management and custom allocator 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-07 05:20 -0800

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