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From Mark Eggers <its_toas...@yahoo.com>
Subject Re: Tomcat dies suddenly
Date Sun, 07 Feb 2010 02:46:46 GMT
--- On Fri, 2/5/10, Carl <carl@etrak-plus.com> wrote:

Carl,

> 1. The application runs fine on an older system. Do we have
> the glibc and kernel versions for all systems?
> 
> The old system: P4.  1GB memory, 1.3GB swap. 
> Uses swap on a regular basis.  kernel is 2.4.25. 
> Java is 1.5.0_01-b08.  Tomcat is 5.5.23.  Glibc is
> version 2.3..1.
> 
> New systems: Server A (Dell T110) is a Xeon 3440, sever B
> (Dell T105) is an AMD.  A has 4GB memory and 19GB swap
> which is never used.  B has 6GB memory and 10GB swap
> which is never used.  A and B both use kernel version
> 2.6.29.6, Java 1.6.0_18-b07 and Tomcat 6.0.24..  Glibc
> version is 4.3.3 for both A and B.

A couple of observations here:

Both the old new kernels end in odd numbers. From memory, I thought the odd kernel numbers
were experimental, while the even numbers were production or mainline. I don't remember when
this numbering system took place, but certainly by the time the 2.6 kernels were released.

From kernel.org, I didn't see a 2.6.29 release marked as stable.

The thread implementation has changed between the 2.4 and 2.6 kernels. You can see the thread
implementation change by running:

getconf GNU_LIBPTHREAD_VERSION

I'd be interested in knowing the result of that and

getconf GNU_LIBC_VERSION

on both systems, since I don't recognize 4.3.3 as a glibc version (latest stable is 2.11.1,
so I'm assuming 2.4.3.3?).

glibc has some thread bugs that were fixed, but not until 2.8 or 2.9. There was also a persistent
bug for 32-bit systems that bites Java applications (not your concern since you're running
64-bit) that wasn't fixed until 2.10.1.

So in short, I'm guessing this may be a glibc NPTL issue.

There are some observations that don't match, in that you're using Java 6 (most problems are
reported with Java 1.4 and Java 5), and that you've used OpenSuSE (kernel, glibc version?)
with the same Tomcat failure.

However:

For some of the earlier 2.6 kernels, you could get around NPTL problems by setting this environment
variable:

export LD_ASSUME_KERNEL=2.4.1

which forces the use of the old linuxthreads model. I don't know if that option is available
with the 2.6 kernel that you are using.

Another work-around has been posted on the Java bugs forum, albeit for a different threading
problem and Java 5:

-XX:ParallelGCThreads=1

sets GC to single threads. It's not fixed in the Java bugs database, because later versions
of RedHat Linux don't exhibit the SIGSEGV problem.

Some people report that single-threading GC solves their problems, while other people report
that it doesn't.

Some things to try I guess:

1. export LD_ASSUME_KERNEL=2.4.1 (maybe in startup.sh?) if your kernel supports this..

2. set -XX:ParallelGCThreads=1 in catalina.sh (JAVA_OPTS). This is an experimental switch,
not documented here: http://java.sun.com/javase/technologies/hotspot/vmoptions.jsp, but documented
here: http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html

3. Move to an even-numbered kernel with a glibc of 2.10.1 or better. 2.10 might be OK for
your environment since the bug fixed in 2.10.1 causes problems for 32-bit systems only.

just my two cents . . . .

/mde/


      


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