By default many Linux network interface card drivers set their SMP affinity mask to either all zeroes or all ones (“ff” — the length of the mask depends on the number of CPUs on the system). The former results in all queues and interfaces running on CPU ID 0, which can become a performance bottleneck due to insufficient computing power. The latter results in all queues and interfaces being scheduled on multiple CPUs, which can become a performance bottleneck due to increased CPU memory cache misses. (more…)
If you have already upgraded to
jessie and have
init, you can switch back with these commands:
apt-get install -y sysvinit-core reboot apt-get purge -y systemd
sysvinit works better on my servers, as daemons have a chance of doing their own graceful shutdown before the network is brought down.
Before upgrading to
Package: systemd-sysv Pin: release o=Debian Pin-Priority: -1
See also: How to stay with sysvinit in Debian Jessie by Petter Reinholdtsen
I’m not sure what failed last night, but I’m guessing the cable Internet connection was down. Interestingly, unbound had stopped resolving even local zones configured with
stub-addr directives. This was unexpected: stub-zones are supposed to work “without referring to the public Internet” per the
unbound.conf manual page.
To mitigate the issue I wanted to have backup name servers in
resolv.conf (ones using a different Internet connection) even on the resolving name server hosts themselves. With resolvconf that boiled down to creating
/etc/default/resolvconf with the following setting in it:
This way name servers configured in
dns-nameservers directives) are included in
resolv.conf even when unbound has been started.
However, this is a poor workaround, as I don’t have multiple Internet connections at every site.
Debian 7.0 “wheezy” was officially released about a week ago. I’ve been running it on a couple of systems for a few months already because of the more recent software versions available on it. Today I upgraded one of the shell servers, a couple of days ahead of the originally posted schedule due to security updates to MySQL (DSA-2667). As usual for Debian, the upgrade process is well documented1 and robust. However, here are some notes for upgrading the next instance. (more…)
I just patched a couple of ESXi hosts to 4.0.0 build 256968 and found that VMware Tools were no longer loading after upgrading them. After some digging everything is more or less back to normal. (more…)
I’ve been observing a really strange problem on Ubuntu Server 8.04: processes are sitting in limbo not doing anything. I first observed this as phones losing their SIP registrations periodically (but at random intervals).
When debugging the issue, I saw that a
ping running on the system would often just sit there, not sending more packets, sometimes for seconds on end (I didn’t always wait to see if it would ever continue). Since hitting a key on the keyboard would immediately be echoed back, it wasn’t a problem with the terminal or ssh connection. Pinging the system from another would work without problems. Interrupting
ping would report no packet loss (which was true — you can’t lose replies to packets you didn’t send).
My best guess is that the alternative scheduler chosen by the Ubuntu developers for the server kernels doesn’t work as intended on AMD CPUs (or just the Athlon XP, or some other part of the hardware I’m using).
My “fix” was to switch to Debian 5.0 (lenny), which doesn’t exhibit this problem at all.
I could have tried with the desktop edition of Ubuntu, but can’t really spare the time right now. Especially since I now have something that works reliably again.
I did try with different network hardware, though. I was originally using an SMC card based on
ns83820 (but for some reason not reporting anything at all with
ethtool — works fine with the
gsip driver on NetBSD). I then switched to a Netwjork “brand” card based on
r8169 (well liked by
ethtool). No difference, but stayed with the latter (working
ethtool is always nice).
- Being on the road is a challenge to my music listening habits: no Squeezebox and no Spotify. I’ve managed ok with my iPods and Last.fm streaming. However, there’s been no good reason to miss Spotify, though, even when running Ubuntu on the laptop. Just follow the instructions to install and run Spotify under Wine.
- “Suddenly” Firefox had begun to pin the CPU at 100% even when not doing anything. I started to uninstall related recently added software. Looks like the culprit was
swfdec-mozilla, which I had added hoping to get Cooliris working (no such luck — didn’t work with
flashplugin-installereither). No flash now, but also no load when browsing the web. (And no burning sensation from the laptop.)
Just a short note on getting a minimal Asterisk environment installed on current versions of Debian and Ubuntu:
aptitude install asterisk m-a a-i zaptel modprobe ztdummy
/etc/modules so it gets loaded when the system starts.
m-a command is not found, install the