Hi all,
I am using Sarge on AMD64 (dual Opteron). I noticed recently that there
were some issues with the stock version of Perl - "v5.8.4 built for
x86_64-linux-thread-multi". Messages were appearing in my apache error
log every time a child process terminated, to the effect that "2 or more
threads are running". I wasn't starting multiple threads, so this always
mystified me. At the same time, I was noticing that at times of higher
webserver load, the CPU "system" load and fork rates were spiking
unreasonably (going to over 120 forks per second). I had a suspicion
about the multithreaded perl, as I had never seen this before on my
previous servers, which had the same software setup (2.6 kernel, apache
1.3.x), except that they had had non-multi-threaded Perl installed.
I am no expert on debian packages, and I couldn't find any references on
the Web for either getting pre-built non-threaded Perl, or how to build
a debian package for it. The process for getting Perl 5.8.8 from
unstable or testing scared me, because it seemed that the package had
dependencies that would mean a whole lot of other stuff might need to
also be upgraded. Also, I assume that the newer versions would also be
multithreaded, which wouldn't help all that much if threading is the
problem. I don't really fancy upgrading a lot of core packages to
testing or unstable on my production server, which is unfortunately the
only AMD64 (or debian for that matter) box I have access to. My
workstation is slackware.
So I decided to try building my own non-threaded Perl, from source. I
got the source for 5.8.8 from perl.org, and it built ok as non-threaded,
and I was able to get apache with mod_perl built using it. I also had to
re-build all my perl modules, but that was ok. The thread error messages
disappeared from the apache logs, and munin now shows that the CPU
spikes have all but disappeared (you can still see a rise in CPU usage
and forkrate when the web traffic increases, but it is nothing like the
spikes we had before). So I guess this helped fix the problem, for
whatever reason.
However I quickly discovered that by replacing the Debian Perl with my
own, it broke a bunch of stuff, such as apt-get. I got all kinds of
errors because things like deb-conf appeared to now be broken with the
new perl. I couldn't find out easily what was missing - no reference to
deb-conf or the other stuff that was missing on CPAN, and Debian itself
seemed to be very confused because it thought its Perl should be there,
but it wasn't.
I tried removing the Debian version of Perl, to make it cleaner so that
the new one was the only version lying around, but quickly discovered
that dozens of other packages depend on it - I would end up also
removing all manner of essential utilities. So I obviously have to leave
the Debian Perl in place.
I ended up building apache with my new perl, but then afterward
re-instated the /usr/bin/perl with the old version. This appeared to
make everything work again with apt-get, but my apache is still using
the newer version. I don't like this, it seems very kludgy and rickety -
when I need to build apache again, I'll have to remember to temporarily
re-instate my new version during the build.
Obviously there are issues with building your own perl, but I'm sure it
must be possible to do it using the "official Debian way". Can anyone
give me a step-by-step instructions on how you're supposed to build your
own Perl on a Debian system, while still keeping everything happy?
Thanks!
/Neil
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- Building my own Perl on Sarge AMD64 Neil Gunton
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