Re: Advice Required - for avoiding conflict betwen qmail-smtpd, rblsmtpd loaded as shared objects in tcpserver

On 2 April 2017 at 20:47, Charles Cazabon
<[email protected]> wrote:
> Manvendra Bhangui <[email protected]> wrote:
>> On 1 April 2017 at 22:36, Charles Cazabon wrote:
>>
>> > reasonable operating systems and even vaguely-modern hardware.  Do you
>> > actually have data showing that this minimal overhead is a bottleneck in
>> > your situation?  If not, why are you trying to eliminate it?
>>
>> I do have a situation where I open around 23 control files in the
>> qmail-smtpd process. I want to move this to the main() of the
>> tcpserver process and avoid loading it again and again.
> [...]
>> No I do not have any data. It is definitely not a bottleneck. It's
>> just that the idea of loading the control files just once does look
>> good.
>
> I'm afraid you're fooling yourself.  Any control files that are opened and
> read regularly - i.e. if you're getting at least a few SMTP connections every
> minute - will be satisfied from the cache.  And qmail's reading of those files
> doesn't use a lot of CPU time or other resources.
>
> So you aren't really saving CPU, or anything else for that matter.   You've
> just introduced complexity, and probably security problems, for no real
> benefit.
>
> 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.

Would want to try this. I have heard about smtp-source and smtp-sink
but never used them. Any recommendations?