Date: Sat, 7 Mar 2009 13:08:56 -0800 (PST) From: Martin Badie <martinbadie@yahoo.com> To: freebsd-hackers@freebsd.org Subject: select.h FD_SETSIZE and Qmail-Postfix test Message-ID: <67469.69113.qm@web59906.mail.ac4.yahoo.com>
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Hi,
There is a test that I am doing with FreeBSD and Linux. This test involves qmail and postfix comparison. Both FreeBSD and Linux seems to have 1024 File Descriptor limit. (FD_SETSIZE in select.h in FreeBSD) .
To have a better concurrency in qmail on smtp level. I have used a patch named big-todo patch also used big-concurrency patch. These patches helps me to increase concurrency in operating system. I set concurrent connection to 500(tcpserver -c 500). There is no problem until around 400-500 active smtp connection. But if the total smtp connection exceeds 500, load average increases to ~40-50 but cpu system time arises to %50-60. The strange issue is that, this load increases when the connection is limited to accept 500 connections but the tool I use is configured to 700 (more than 500) connections. Normally ucspi-tcp software limits connection to 500 ( -c 500) I suspect it is something to do with Operating system level.
Additionally I have also patched FreeBSD kernel with 4096 FD_SETSIZE in select.h in kernel and booted with that kernel. I have also compiled qmail from scratch to accept 2040 connections (in conf-spawn) but there is no change I mean I still can't get more than decent 500 connections with acceptable load average.
I have also used postfix on both Linux FreeBSD:
default_process_limit = 500
smtpd_client_connection_count_limit = 500
but I still get strange load when connection raises more than 500
I suspect something is missing or need to be configured on the operating system level (both Linux and FreeBSD)
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