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List:       postfix-users
Subject:    Re: postfix milter body chunk length
From:       Wietse Venema <wietse () porcupine ! org>
Date:       2019-08-19 11:10:27
Message-ID: 46BrnH6zW1zJrNs () spike ! porcupine ! org
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Matthias Schneider:
> Chris, can you tell me your postfix version/settings?
> 
> When i do a load-test on my milter application, i can also get 100mb in 
> about a second proceesed (with 65535 sized chunks).
> 
> But postfix (3.3.0 and 3.4.5) only sends about 24 body chunks per second 
> to my milter application. Its the only milter configured and the milter 
> is running on 127.0.0.1 (so no latency issues)

Obviously, Postfix can send faster than that, as witnessed by various
people on the mailing list. The Postfix Milter implementation has
not changed in years.

I suspect that the bottleneck is on the receiving side.

- Maybe the loopback stack does not like the 65535 block size. Try
using an ethernet interface address instead.

- Maybe the application "appends" the new content to the end of a
large string; that requires allocating and copying huge amounts of
memory each time. That alone may explain the difference in program
speed.

- Maybe the above program behavior triggers a worst case in the
malloc library as it needs to deal with copies of strings of
increasing length.

You can test that with a test program that does nothing with the
data, such as the test-milter program that is part of Postfix
source code.

	Wietse
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