Re: Max thread/session timeouts

2005-08-11 Thread Michael Kleinhenz
Peddireddy,

how about your project? I have finally found a solution here ;-) If the
database handles requests faster, the load on my Tomcat(s) are lower,
because of the lower count of active threads. This does not resolve the
problem induced by the apparent connection limit on Windows 2003
Standard Edition, especially in peak situations with ~3000 active
Threads. I've got the computing centre to install Red Hat Enterprise 4
on one of the servers and voila, the errors are gone!

Admittedly, it seems that Linux is a bit slower when getting into a high
thread count, it's sufficiently fast for my project. Also, it seems
faster on low thread counts (500). A simple servlet building a XML tree
(without any database access or other 3rd party access) runs about 30%
faster on Linux than on Windows on the same machine.

I think the slower response of Linux with high thread counts is induced
by a slower thread handling. An engineer from Red Hat will try to
optimize that tomorrow..

-- Michael


On Fri, Jul 22, 2005 at 11:23:24AM +0200, Michael Kleinhenz wrote:
 Peddireddy,
 
  your mail is very informative.
  we have a very similar set up (4 Xeon processors 3.5 GB Ram and
  WIn2003 Standard edition) and hardpart is that we cant change this
  setup and switch to Linux. 
 
 same problem over here. The computing centre of our client can't provide
 Linux servers. I'm struggling with this problem for 3 weeks now.
 
  I heard about clustering on diferent boxes. Is the process of running
  multiple tomcats on a single machine will be same??
 
 My experience was that with a single Tomcat on a large machine, you'll
 never use that box fully. Besides that you can't get the Sun JVM to
 accept a large amount of threads while giving them enough memory, Tomcat
 seems to have performance problems with 3000+ threads busy at the same
 time. The BEA JVM (JRockit) performs better in terms of memory and
 threads but is slower than the Sun JVM. If you have rather complex
 database operations performed by your webapp, this will get you into
 trouble, because if there is a single bottleneck in the whole system,
 the requests will pile up in the server, it hits its thread limit, and
 ceases operation.
 
 So, I have made good experiences with 4 Tomcats on a 2xXeon with 4GB.
 The server's load is somewhere between 70% and 100% while running with
 high load and can handle more concurrent requests than a single Tomcat.
 
  You talked about some workarounds using esoteric registry keys, can
  you eloborate on this or tell me where I can get details about it and
  the details about limitations placed by windows2003  on a single
  process in terms of number of threads, memory etc.
 
 We use 2003 Standard Edition and get the following limitations:
 
  . Windows only provides 2GB memory to all applications running,
regardless of how much memory you have. All other memory is used for
Windows itself. With a registry key, you can extend this to 3GB. I
don't have the key handy, but it can be found in MSDN.
 
  . The somewhat larger problem is the crappy TCP stack on Windows. A
single Tomcat easily handles 1000 concurrent connections, but if I start
4 Tomcats, I get a WSAENOBUFS error (An operation on a socket could not
be performed because the system lacked sufficient buffer space or
because a queue was full) at about 3300 concurrent connections.
Because each Tomcat runs with his own instance of the JVM, I suppose
the problem is Windows, the network or anything else that is used by all
Tomcats at the same time. Even worse, after such a crash, there is a
10% chance, the Tomcats not resuming normal operation but crashes
completely.
 
  . Windows has a default limit of 5000 ephemeral ports that can be used 
fo outgoing connections. This can be changed with the MaxUserPorts
registry key. Also, the TcpTimedWaitDelay key is relevant for network
performance. Both are described here:
 

 http://msdn.microsoft.com/library/en-us/randz/protocol/tcp_time-wait_delay.asp
 
 I'm now really irritated by this problem. I need a capacity of about
 15000 concurrent connections for my project. I also have 3 2xXeon
 servers here, but windows (or anything else) doesn't allow more than
 ~8000 connections until it dies.
 
 -- Michael
 
 -- 
 Dipl.-Technoinform. Michael Kleinhenz
 tarent GmbH . Bahnhofstr. 13 . 53123 Bonn
 fon +49 (228) / 52 67 5-0 . fax +49 (228) / 52 67 5-25

-- 
Michael Kleinhenz
tarent GmbH . Bahnhofstr. 13 . 53123 Bonn
fon +49 (228) / 52 67 5-0 . fax +49 (228) / 52 67 5-25

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Re: Max thread/session timeouts

2005-07-22 Thread Peddireddy Srikanth
Michael,

your mail is very informative.
we have a very similar set up (4 Xeon processors 3.5 GB Ram and
WIn2003 Standard edition) and hardpart is that we cant change this
setup and switch to Linux. So what you told Tomcat on Windows doesn't
scale well is bothering me

I heard about clustering on diferent boxes. Is the process of running
multiple tomcats on a single machine will be same??
You talked about some workarounds using esoteric registry keys, can
you eloborate on this or tell me where I can get details about it and
the details about limitations placed by windows2003  on a single
process in terms of number of threads, memory etc.

Thanks in advance.

With regards
Srikanth.P

On 7/22/05, Michael Kleinhenz [EMAIL PROTECTED] wrote:
 
   We're running an application on Tomcat that often hits the limit of
  150 threads.  Can someone with experience changing this value give me
  advice on it?  How big can you make this number?  How much extra memory
  do I need if I say change it to, say, 500?  Thanks.
 
 just a few facts on threads in Tomcat:
 
  . you'll need (Xss*max_threads)+Xmx+x memory in your box, where x is
the memory needed by the basic JVM tasks besides the thread space
(say, 100MB).
 
  . on ia32/Windows, you can only assign 1.6GB (Xmx-)memory to a single
JVM. A value above it will break the 2GB barrier and will not run.
 
  . you need to find the balance between max_threads and Xmx. A lower Xmx
gives you a higher max_threads and vice versa.
 
  . Tomcat on Windows doesn't scale well. Use multiple Tomcat instances
on one box if you have a large box. In my setup, I run 4 Tomcats on a
2xXeon system with 4GB memory. Each Tomcat gets 1000 threads and
512MB. This is _much_ faster than a single Tomcat with all
memory and 4000 threads.
 
  . Windows 2003 Server, at least the Standard Edition has major
limitations in both TCP connections and memory. There are some
workarounds using esoteric registry keys, but none of them works
well. Windows is a crippled desktop os that wants to be on the
server. If you want really high performance on large boxes, use
Linux (Kernel 2.6!). You even get a better administration
interface. Hate this inefficient administration-by-clicking ;-)
 
 -- Michael
 
 --
 Dipl.-Technoinform Michael Kleinhenz
 tarent GmbH . Bahnhofstraße 13 . 53123 Bonn
 fon: +49 (228) / 52 67 5-0
 fax: +49 (228) / 52 67 5-25
 
 
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 To unsubscribe, e-mail: [EMAIL PROTECTED]
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Re: Max thread/session timeouts

2005-07-22 Thread Michael Kleinhenz
Peddireddy,

 your mail is very informative.
 we have a very similar set up (4 Xeon processors 3.5 GB Ram and
 WIn2003 Standard edition) and hardpart is that we cant change this
 setup and switch to Linux. 

same problem over here. The computing centre of our client can't provide
Linux servers. I'm struggling with this problem for 3 weeks now.

 I heard about clustering on diferent boxes. Is the process of running
 multiple tomcats on a single machine will be same??

My experience was that with a single Tomcat on a large machine, you'll
never use that box fully. Besides that you can't get the Sun JVM to
accept a large amount of threads while giving them enough memory, Tomcat
seems to have performance problems with 3000+ threads busy at the same
time. The BEA JVM (JRockit) performs better in terms of memory and
threads but is slower than the Sun JVM. If you have rather complex
database operations performed by your webapp, this will get you into
trouble, because if there is a single bottleneck in the whole system,
the requests will pile up in the server, it hits its thread limit, and
ceases operation.

So, I have made good experiences with 4 Tomcats on a 2xXeon with 4GB.
The server's load is somewhere between 70% and 100% while running with
high load and can handle more concurrent requests than a single Tomcat.

 You talked about some workarounds using esoteric registry keys, can
 you eloborate on this or tell me where I can get details about it and
 the details about limitations placed by windows2003  on a single
 process in terms of number of threads, memory etc.

We use 2003 Standard Edition and get the following limitations:

 . Windows only provides 2GB memory to all applications running,
   regardless of how much memory you have. All other memory is used for
   Windows itself. With a registry key, you can extend this to 3GB. I
   don't have the key handy, but it can be found in MSDN.

 . The somewhat larger problem is the crappy TCP stack on Windows. A
   single Tomcat easily handles 1000 concurrent connections, but if I start
   4 Tomcats, I get a WSAENOBUFS error (An operation on a socket could not
   be performed because the system lacked sufficient buffer space or
   because a queue was full) at about 3300 concurrent connections.
   Because each Tomcat runs with his own instance of the JVM, I suppose
   the problem is Windows, the network or anything else that is used by all
   Tomcats at the same time. Even worse, after such a crash, there is a
   10% chance, the Tomcats not resuming normal operation but crashes
   completely.

 . Windows has a default limit of 5000 ephemeral ports that can be used 
   fo outgoing connections. This can be changed with the MaxUserPorts
   registry key. Also, the TcpTimedWaitDelay key is relevant for network
   performance. Both are described here:

   
http://msdn.microsoft.com/library/en-us/randz/protocol/tcp_time-wait_delay.asp

I'm now really irritated by this problem. I need a capacity of about
15000 concurrent connections for my project. I also have 3 2xXeon
servers here, but windows (or anything else) doesn't allow more than
~8000 connections until it dies.

-- Michael

-- 
Dipl.-Technoinform. Michael Kleinhenz
tarent GmbH . Bahnhofstr. 13 . 53123 Bonn
fon +49 (228) / 52 67 5-0 . fax +49 (228) / 52 67 5-25

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Re: Max thread/session timeouts

2005-07-22 Thread Peddireddy Srikanth
Hi Michael,
Thanks for the information.
I will try to further study this problem and let you know if I found
anything useful.
Mean while can you let me know about any JVM options that you are
using for running your tomcat and that you think will be useful in
server performance and scalability. So that I can check whether any
one of them are applicable in our context.

regards
Srikanth Peddireddy. 

On 7/22/05, Michael Kleinhenz [EMAIL PROTECTED] wrote:
 Peddireddy,
 
  your mail is very informative.
  we have a very similar set up (4 Xeon processors 3.5 GB Ram and
  WIn2003 Standard edition) and hardpart is that we cant change this
  setup and switch to Linux.
 
 same problem over here. The computing centre of our client can't provide
 Linux servers. I'm struggling with this problem for 3 weeks now.
 
  I heard about clustering on diferent boxes. Is the process of running
  multiple tomcats on a single machine will be same??
 
 My experience was that with a single Tomcat on a large machine, you'll
 never use that box fully. Besides that you can't get the Sun JVM to
 accept a large amount of threads while giving them enough memory, Tomcat
 seems to have performance problems with 3000+ threads busy at the same
 time. The BEA JVM (JRockit) performs better in terms of memory and
 threads but is slower than the Sun JVM. If you have rather complex
 database operations performed by your webapp, this will get you into
 trouble, because if there is a single bottleneck in the whole system,
 the requests will pile up in the server, it hits its thread limit, and
 ceases operation.
 
 So, I have made good experiences with 4 Tomcats on a 2xXeon with 4GB.
 The server's load is somewhere between 70% and 100% while running with
 high load and can handle more concurrent requests than a single Tomcat.
 
  You talked about some workarounds using esoteric registry keys, can
  you eloborate on this or tell me where I can get details about it and
  the details about limitations placed by windows2003  on a single
  process in terms of number of threads, memory etc.
 
 We use 2003 Standard Edition and get the following limitations:
 
  . Windows only provides 2GB memory to all applications running,
   regardless of how much memory you have. All other memory is used for
   Windows itself. With a registry key, you can extend this to 3GB. I
   don't have the key handy, but it can be found in MSDN.
 
  . The somewhat larger problem is the crappy TCP stack on Windows. A
   single Tomcat easily handles 1000 concurrent connections, but if I start
   4 Tomcats, I get a WSAENOBUFS error (An operation on a socket could not
   be performed because the system lacked sufficient buffer space or
   because a queue was full) at about 3300 concurrent connections.
   Because each Tomcat runs with his own instance of the JVM, I suppose
   the problem is Windows, the network or anything else that is used by all
   Tomcats at the same time. Even worse, after such a crash, there is a
   10% chance, the Tomcats not resuming normal operation but crashes
   completely.
 
  . Windows has a default limit of 5000 ephemeral ports that can be used
   fo outgoing connections. This can be changed with the MaxUserPorts
   registry key. Also, the TcpTimedWaitDelay key is relevant for network
   performance. Both are described here:
 
   
 http://msdn.microsoft.com/library/en-us/randz/protocol/tcp_time-wait_delay.asp
 
 I'm now really irritated by this problem. I need a capacity of about
 15000 concurrent connections for my project. I also have 3 2xXeon
 servers here, but windows (or anything else) doesn't allow more than
 ~8000 connections until it dies.
 
 -- Michael
 
 --
 Dipl.-Technoinform. Michael Kleinhenz
 tarent GmbH . Bahnhofstr. 13 . 53123 Bonn
 fon +49 (228) / 52 67 5-0 . fax +49 (228) / 52 67 5-25
 
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RE: Max thread/session timeouts

2005-07-22 Thread Darek Czarkowski
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Max thread/session timeouts

2005-07-21 Thread Kenneth Litwak
  We're running an application on Tomcat that often hits the limit of
150 threads.  Can someone with experience changing this value give me
advice on it?  How big can you make this number?  How much extra memory
do I need if I say change it to, say, 500?  Thanks.

 

Ken



Re: Max thread/session timeouts

2005-07-21 Thread Darryl L. Miles

Kenneth Litwak wrote:


 We're running an application on Tomcat that often hits the limit of
150 threads.  Can someone with experience changing this value give me
advice on it?  How big can you make this number?  How much extra memory
do I need if I say change it to, say, 500?  Thanks.
 

I take it you know the 150 is the default limt in the config/server.xml 
and this can be upped towards you operating system platform maximum.


A ball park of your applications memory needs @150 threads is better 
chcked by simply looking at the paged in size while under that load (the 
RSS size in ps uaxw under Unix).  You can't expect us to guess exactly 
how much more memory you need from the information you've given, I mean 
you've not told us if you already have 8Gb of RAM installed or just 32Mb 
for us to at least take a guess at the answer.


Maybe the Java VM -Xss is a useful option to look at, but I think 
providing you are not hitting your upper limit on a single process 
memory usage (into the 3/4Gb realm on 32bit) for a high number of 
threads then it will make little difference.  As I believe stack space 
just like other application memory is paged in as its used and reducing 
the stack space to a lower limit than your application need will just 
make it crash.


--
Darryl L. Miles



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Re: Max thread/session timeouts

2005-07-21 Thread J. Ryan Earl
As a reference, in conf/server.xml I set my thread limit to 1 max 
threads, 1000 max idle threads, and 100 on startup.  I've seen my as 
many as 7K threads busy within my application.  This is on a 32bit 2.6 
Linux kernel with 2GB of RAM (-Xmx1500m).  On the 2.4 kernel I found 
practical limitations in how many threads the kernel could multiplex 
between, saw frequent system hangs under high load where the whole 
server would become unusable.


On either linux kernel, you probably want to increase your maximum 
number of file descriptors in /etc/security/limits.conf for your Tomcat 
user account(s).  16K nofile as default works great for me.


How much more memory you need really depends on your application.  500 
threads isn't that much memory overhead, but if each thread goes off and 
creates a bunch of objects while it's working you'll need to assure 
heapspace is available accordingly.  The short answer is: try it out, 
play with it.  500 threads isn't a whole lot.


-ryan

Kenneth Litwak wrote:


 We're running an application on Tomcat that often hits the limit of
150 threads.  Can someone with experience changing this value give me
advice on it?  How big can you make this number?  How much extra memory
do I need if I say change it to, say, 500?  Thanks.



Ken
 



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Re: Max thread/session timeouts

2005-07-21 Thread Michael Kleinhenz

  We're running an application on Tomcat that often hits the limit of
 150 threads.  Can someone with experience changing this value give me
 advice on it?  How big can you make this number?  How much extra memory
 do I need if I say change it to, say, 500?  Thanks.

just a few facts on threads in Tomcat:

  . you'll need (Xss*max_threads)+Xmx+x memory in your box, where x is
the memory needed by the basic JVM tasks besides the thread space
(say, 100MB).

  . on ia32/Windows, you can only assign 1.6GB (Xmx-)memory to a single
JVM. A value above it will break the 2GB barrier and will not run.

  . you need to find the balance between max_threads and Xmx. A lower Xmx
gives you a higher max_threads and vice versa.

  . Tomcat on Windows doesn't scale well. Use multiple Tomcat instances
on one box if you have a large box. In my setup, I run 4 Tomcats on a
2xXeon system with 4GB memory. Each Tomcat gets 1000 threads and
512MB. This is _much_ faster than a single Tomcat with all
memory and 4000 threads.

  . Windows 2003 Server, at least the Standard Edition has major
limitations in both TCP connections and memory. There are some
workarounds using esoteric registry keys, but none of them works
well. Windows is a crippled desktop os that wants to be on the
server. If you want really high performance on large boxes, use
Linux (Kernel 2.6!). You even get a better administration
interface. Hate this inefficient administration-by-clicking ;-)

-- Michael

-- 
Dipl.-Technoinform Michael Kleinhenz
tarent GmbH . Bahnhofstraße 13 . 53123 Bonn
fon: +49 (228) / 52 67 5-0
fax: +49 (228) / 52 67 5-25


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Re: Max thread/session timeouts

2005-07-21 Thread Andrew Miehs
Ouch! Thats a LOT of threads - I can't believe your box still performs 
well with this many threads - or have you enabled keep-alives?


The number of threads really depends on your application. I have max 
threads set to 750, or our 32bit 2.6 Linux systems. Our thread count 
normally doesn't go over 200. When the servers need to wait for the 
backend, and the requests start to queue (heading towards 1000) - you 
will end up with a huge problem anyway, as it is probably unlikely that 
your backend servers/ database, etc, will be able to catch up  with the 
requests, but as I said, that depends how and what your application does.


Andrew

J. Ryan Earl wrote:

As a reference, in conf/server.xml I set my thread limit to 1 max 
threads, 1000 max idle threads, and 100 on startup.  I've seen my as 
many as 7K threads busy within my application.  This is on a 32bit 2.6 
Linux kernel with 2GB of RAM (-Xmx1500m).  On the 2.4 kernel I found 
practical limitations in how many threads the kernel could multiplex 
between, saw frequent system hangs under high load where the whole 
server would become unusable.


On either linux kernel, you probably want to increase your maximum 
number of file descriptors in /etc/security/limits.conf for your 
Tomcat user account(s).  16K nofile as default works great for me.


How much more memory you need really depends on your application.  500 
threads isn't that much memory overhead, but if each thread goes off 
and creates a bunch of objects while it's working you'll need to 
assure heapspace is available accordingly.  The short answer is: try 
it out, play with it.  500 threads isn't a whole lot.





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RE: Max thread/session timeouts

2005-07-21 Thread Warren Taylor
Take me off this fucking list.

WARREN TAYLOR
Sunbelt Business Advisors
Sunbelt Business Brokers of MS
www.sunbeltnetwork.com

-Original Message-
From: Andrew Miehs [mailto:[EMAIL PROTECTED] 
Sent: Thursday, July 21, 2005 5:00 PM
To: Tomcat Users List
Subject: Re: Max thread/session timeouts

Ouch! Thats a LOT of threads - I can't believe your box still performs 
well with this many threads - or have you enabled keep-alives?

The number of threads really depends on your application. I have max 
threads set to 750, or our 32bit 2.6 Linux systems. Our thread count 
normally doesn't go over 200. When the servers need to wait for the 
backend, and the requests start to queue (heading towards 1000) - you 
will end up with a huge problem anyway, as it is probably unlikely that 
your backend servers/ database, etc, will be able to catch up  with the 
requests, but as I said, that depends how and what your application does.

Andrew

J. Ryan Earl wrote:

 As a reference, in conf/server.xml I set my thread limit to 1 max 
 threads, 1000 max idle threads, and 100 on startup.  I've seen my as 
 many as 7K threads busy within my application.  This is on a 32bit 2.6 
 Linux kernel with 2GB of RAM (-Xmx1500m).  On the 2.4 kernel I found 
 practical limitations in how many threads the kernel could multiplex 
 between, saw frequent system hangs under high load where the whole 
 server would become unusable.

 On either linux kernel, you probably want to increase your maximum 
 number of file descriptors in /etc/security/limits.conf for your 
 Tomcat user account(s).  16K nofile as default works great for me.

 How much more memory you need really depends on your application.  500 
 threads isn't that much memory overhead, but if each thread goes off 
 and creates a bunch of objects while it's working you'll need to 
 assure heapspace is available accordingly.  The short answer is: try 
 it out, play with it.  500 threads isn't a whole lot.



-
To unsubscribe, e-mail: [EMAIL PROTECTED]
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RE: Max thread/session timeouts

2005-07-21 Thread pacea
Mr. Taylor,
 Not sure how you got on this list.  To remove yourself, scroll to the 
bottom of any one of the messages to which you've replied and click on the 
unsubscribe link.
Warren Pace


 Take me off this fucking list.
 
 WARREN TAYLOR
 Sunbelt Business Advisors
 Sunbelt Business Brokers of MS
 www.sunbeltnetwork.com
 
 -Original Message-
 From: Andrew Miehs [mailto:[EMAIL PROTECTED] 
 Sent: Thursday, July 21, 2005 5:00 PM
 To: Tomcat Users List
 Subject: Re: Max thread/session timeouts
 
 Ouch! Thats a LOT of threads - I can't believe your box still performs 
 well with this many threads - or have you enabled keep-alives?
 
 The number of threads really depends on your application. I have max 
 threads set to 750, or our 32bit 2.6 Linux systems. Our thread count 
 normally doesn't go over 200. When the servers need to wait for the 
 backend, and the requests start to queue (heading towards 1000) - you 
 will end up with a huge problem anyway, as it is probably unlikely that 
 your backend servers/ database, etc, will be able to catch up  with the 
 requests, but as I said, that depends how and what your application does.
 
 Andrew
 
 J. Ryan Earl wrote:
 
  As a reference, in conf/server.xml I set my thread limit to 1 max 
  threads, 1000 max idle threads, and 100 on startup.  I've seen my as 
  many as 7K threads busy within my application.  This is on a 32bit 2.6 
  Linux kernel with 2GB of RAM (-Xmx1500m).  On the 2.4 kernel I found 
  practical limitations in how many threads the kernel could multiplex 
  between, saw frequent system hangs under high load where the whole 
  server would become unusable.
 
  On either linux kernel, you probably want to increase your maximum 
  number of file descriptors in /etc/security/limits.conf for your 
  Tomcat user account(s).  16K nofile as default works great for me.
 
  How much more memory you need really depends on your application.  500 
  threads isn't that much memory overhead, but if each thread goes off 
  and creates a bunch of objects while it's working you'll need to 
  assure heapspace is available accordingly.  The short answer is: try 
  it out, play with it.  500 threads isn't a whole lot.
 
 
 
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 To unsubscribe, e-mail: [EMAIL PROTECTED]
 For additional commands, e-mail: [EMAIL PROTECTED]
 
 
 
 
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 To unsubscribe, e-mail: [EMAIL PROTECTED]
 For additional commands, e-mail: [EMAIL PROTECTED]
 

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Re: Max thread/session timeouts

2005-07-21 Thread Larry Meadors
Whoa! Someone forgot to take their meds today...

To unsubscribe, e-mail:
[EMAIL PROTECTED]http://a.apache.org

Larry


On 7/21/05, Warren Taylor [EMAIL PROTECTED] wrote:
 To unsubscribe, e-mail: [EMAIL PROTECTED]


RE: Max thread/session timeouts

2005-07-21 Thread Warren Taylor
There is no unsubscribe link.

WARREN TAYLOR
Sunbelt Business Advisors
Sunbelt Business Brokers of MS
www.sunbeltnetwork.com

-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] 
Sent: Thursday, July 21, 2005 5:06 PM
To: Tomcat Users List
Subject: RE: Max thread/session timeouts

Mr. Taylor,
 Not sure how you got on this list.  To remove yourself, scroll to the
bottom of any one of the messages to which you've replied and click on the
unsubscribe link.
Warren Pace


 Take me off this fucking list.
 
 WARREN TAYLOR
 Sunbelt Business Advisors
 Sunbelt Business Brokers of MS
 www.sunbeltnetwork.com
 
 -Original Message-
 From: Andrew Miehs [mailto:[EMAIL PROTECTED] 
 Sent: Thursday, July 21, 2005 5:00 PM
 To: Tomcat Users List
 Subject: Re: Max thread/session timeouts
 
 Ouch! Thats a LOT of threads - I can't believe your box still performs 
 well with this many threads - or have you enabled keep-alives?
 
 The number of threads really depends on your application. I have max 
 threads set to 750, or our 32bit 2.6 Linux systems. Our thread count 
 normally doesn't go over 200. When the servers need to wait for the 
 backend, and the requests start to queue (heading towards 1000) - you 
 will end up with a huge problem anyway, as it is probably unlikely that 
 your backend servers/ database, etc, will be able to catch up  with the 
 requests, but as I said, that depends how and what your application does.
 
 Andrew
 
 J. Ryan Earl wrote:
 
  As a reference, in conf/server.xml I set my thread limit to 1 max 
  threads, 1000 max idle threads, and 100 on startup.  I've seen my as 
  many as 7K threads busy within my application.  This is on a 32bit 2.6 
  Linux kernel with 2GB of RAM (-Xmx1500m).  On the 2.4 kernel I found 
  practical limitations in how many threads the kernel could multiplex 
  between, saw frequent system hangs under high load where the whole 
  server would become unusable.
 
  On either linux kernel, you probably want to increase your maximum 
  number of file descriptors in /etc/security/limits.conf for your 
  Tomcat user account(s).  16K nofile as default works great for me.
 
  How much more memory you need really depends on your application.  500 
  threads isn't that much memory overhead, but if each thread goes off 
  and creates a bunch of objects while it's working you'll need to 
  assure heapspace is available accordingly.  The short answer is: try 
  it out, play with it.  500 threads isn't a whole lot.
 
 
 
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