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

Erwin Hoffmann <[email protected]> Tue, 4 Apr 2017 21:09:04 +0200

Newsgroups	gmane.mail.qmail.general
Message-ID	<[email protected]>

Hi Manvendra,

> Am 04.04.2017 um 19:39 schrieb Charles Cazabon <[email protected]>:
> 
> 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.
> 

Absolutely ACK. And -- according to your list of control files -- at least some of them can be replaced by environment variables and can be merged into one control file (badmail*). This is the way Spamcontrol did it and s/qmail does it. See: http://fehcom.de/sqmail/man/qmail-smtpd.html

regards.
--eh.

PS: Apart from that: a 25K badmail file is ridiculous. Something is wrong with your mail architecture.




Dr. Erwin Hoffmann | FEHCom | http://www.fehcom.de | PGP Key-Id: EE00CF65

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