Re: Benchmarked tcpserver dlopen() -> qmail_smtpd() VS tcpserver --> fork() --> exec qmail-smtpd

Manvendra Bhangui <[email protected]> wrote:
> >
> > I *strongly* urge you to profile the performance of vanilla
> > qmail/tcpserver before you decide to "fix" something and try to make it
> > "look good".  I would bet dollars to doughnuts that you will find you are
> > trying to optimize something which is only responsible for 0.01% of the
> > program's work in the first place.
> >
> > As djb himself says, measure, don't speculate.
> 
> So finally I measured and now I have data, and it so consistent, that
> I too am surprised. Using dlopen() to load the control files in
> tcpserver gives a huge, huge gain

Unexpected.  Have you increased the size of the default buffer used for
reading those files?  IIRC it's 64 bytes, and many patches up it to some tens
of K.  I don't remember if we did that in netqmail.

> qmail-smtpd. In the extreme case where I have loaded a 25 Mib
> badmailfrom

You're Holding It Wrong.

qmail's control-file handling is absolutely, completely, and totally NOT
designed for multi-megabyte files, and is completely unsuited to be used as
such.  Given that, your numbers are completely invalid; you're not using the
correct tool for the job, so it isn't surprising that it doesn't work very
well.

If you need stupidly-large control files, you should be using one of the
patches that replaces the simple in-memory arrays with a CDB lookup.  Your
"overhead" loading these control files will disappear.

Charles
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