Super!
On Tue, 3 Feb 2009, Gilad Ben-Yossef wrote:
Date: Tue, 03 Feb 2009 10:25:14 +0200
From: Gilad Ben-Yossef <gi...@codefidence.com>
To: Jonathan Ben Avraham <y...@tkos.co.il>
Cc: m...@swiftouch.com, ILUG <linux-il@cs.huji.ac.il>
Subject: Re: [YBA] TCP connection rate
Jonathan Ben Avraham wrote:
Hi Marc,
The .NET client has a bug that prevents use of persistent MySQL
connections. The application is already cached up the wazoo.
Where would I look in the kernel to see if it is rejecting the connections
as opposed to MySQL? Or is this just unlikely given that the hardware is
fairly robust?
I don't know of a way to get the statistics from the kernel for that, but
maybe this will help:
"The duration that affects the rate at which new connections are accepted is
the time spent on the queue of pending incoming connections. This duration is
equal to the round trip time for the SYN|ACK message and its ACK response
plus the time taken for the client to process the SYN|ACK message plus the
delay for the server to process the ACK and call *accept()*.
The rate at which new connections can be accepted is equal to the number of
entries which can fit on the listen queue divided by the average length of
time each entry spends on the queue. Therefore, the larger the queue, the
greater the rate at which new connection requests can be accepted."
http://www.linuxjournal.com/files/linuxjournal.com/linuxjournal/articles/023/2333/2333s2.html
Thanks,
- yba
On Mon, 2 Feb 2009, m...@swiftouch.com wrote:
Date: Mon, 2 Feb 2009 18:28:21 +0200 (IST)
From: m...@swiftouch.com
To: Jonathan Ben Avraham <y...@tkos.co.il>
Cc: Gilad Ben-Yossef <gi...@codefidence.com>, ILUG
<linux-il@cs.huji.ac.il>
Subject: Re: [YBA] TCP connection rate
Hi all
Without delving into the stack behaviour, I would try the (potentially)
cheaper route - is there a possibility of amalgamating queries to the
database, thereby reducing the per second metric? Or - perish the thought
(caveat emptor, I am not acquainted with the app) - caching replies at the
client?
I am not sure the netstat trick can work in this case - both since (as YBA
noted) the connexions are brief and because netstat deals with connections
very late in their lifecycle. I am not sure how connexions pending on the
stack would show up.
M
---MAV
Marc. Volovic
+972-54-467-6764
m...@swiftouch.com
Sent from my iPhone
On Feb 2, 2009, at 5:06 PM, Jonathan Ben Avraham <y...@tkos.co.il> wrote:
Hi Gilad,
Thanks. The problem is that the connections are exceedingly short-lived.
By the time I type in "netstat -na" already 1000 of them have come and
gone.
- yba
On Mon, 2 Feb 2009, Gilad Ben-Yossef wrote:
Date: Mon, 02 Feb 2009 16:29:23 +0200
From: Gilad Ben-Yossef <gi...@codefidence.com>
To: Jonathan Ben Avraham <y...@tkos.co.il>
Cc: ILUG <linux-il@cs.huji.ac.il>
Subject: Re: [YBA] TCP connection rate
Jonathan Ben Avraham wrote:
Dear list members,
What limits the rate that the Linux kernel TCP stack can accept new
connections? How is that rate related to the rate that the application
listening on a port can handle the connections? That is, if I try to
connect and get ECONNREFUSED is there a way for me to know if I got it
because the kernel could not handle the connection rate or if I got it
because I had more connection attempts than the backlog parameter of my
listen() call? In other words, do I need to tune the kernel or the
application (MySQL) for the desired high connection rate and how would
I know?
Just check what the value of the backlog parameter is and then use
netstat to watch the application connections when you get ECONNREFUSED
error. If the number of connections in netstat is equal (or at least
very close to) the backlog parameter then it's the backlog parameter,
otherwise it's something else.
Gilad
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