> On 4 Sep 2001 13:17:32 +0200, Matthias Andree <madt.e-technik.uni-dortmund.de> wrote:
>
> > Is the modular nature the cause for reduced memory use or rather the
> > "we don't interpret a ('binary') sendmail.cf file" and "we
> > reconsider common approaches and choose superior schemes"?
>
> I'd say the modular nature causes only code to be loaded into memory
> that's actually used instead of e.g. forking the whole sendmail binary.
>
Hmm, modern unix's do page-demand paging on executables, where pages are not
loaded from disk until they are needed. Also, all program data in memory is
COW after a fork. So forking is in either case just a matter of creating a
copy of a process' proc-table entry, that doen not change by makeing you code
more modulair (even better, one big program to do everything may be cheeper in
forking since you may be able to do the work with less forking that with a
more modulair setup like postfix).

> > I thought copy-on-write pages and similar approaches took care of
> > sendmail's memory use.
>
> Postfix would also benefit from that, so it's memory use would still
> be smaller.
>
Memory useage is primairely determined by the amout of data a process uses +
the code-pages actually used. On PC hardware it is important to have your
program to be as small as possible due to the tiny caches the intel-cpu's
have. On high-end CPU's the L2 cache is ofthen as big as 4MB or bigger and
performance is boosted more by loop-unroling than small footprint.

I leart that sendmail now uses multiple queues to do it's work, like postfix
has allways done. This is probably a performace-winner. Also, in sendmail you
could theoreticaly build your own header-rewriting rules, while the rewriting
in postfix is as good as fixed. Of cource sendmail's flexebility comes at a
price...

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> ralf.hildebrandtinnominate.com innominate AG
> Technical Consultant Don't be afraid of what you see -
> Diplom-Informatiker be afraid of what you don't see!
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>
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