From: aaron_watters at my-dejanews.com (aaron_watters at my-dejanews.com)
Date: Mon, 19 Apr 1999 19:50:52 GMT
Subject: Memory and swapping question
References: <371B5ED8.A9C82170@appliedbiometrics.com>
Message-ID: <7fg1ep$t5s$1@nnrp1.dejanews.com>
Content-Length: 1487
X-UID: 557                                                  

In article <371B5ED8.A9C82170 at appliedbiometrics.com>,
  Christian Tismer <tismer at appliedbiometrics.com> wrote:
> due to a question which came up in the tutor list, I'd like
> to ask if somebody can explain the following:....

<chomp><chomp>timings on making huge lists of integers...

> On my system, creation takes about 10 times as for big/2,
> this is ok. But the del takes at least three times as long.
> Besides the fact that integers are never really disposed but
> build up a freelist, why is deletion so much slower now?

Could be wrong, but this may be a case of a famous database
problem.  The OS (typically) swaps out pages by picking the "least recently
used" page, but when you are decreffing (scanning) a HUGE list of sequentially
allocated objects this guarantees that the page you need next will
be swapped out by the time you get to it. Yikes! Allocation is faster
because you are really only "paging things out" (the first time)
and the write to the disk can be buffered until the disk is
ready, allowing the program to proceed (?I think?).

This is one reason why Oracle and Sybase, etc, like to do their own
memory and disk management ("gimme them sectors -- don't need no
g.d. filesystem, thanks!").  Just a guess, but a not completely
uneducated one.
   -- Aaron Watters
===
stop procrastinating tomorrow.


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