[Lxc-users] Help troubleshooting declining performance / high %SI CPU when running 9 Ubuntu 10.04 LXCs

[Serge E. Hallyn]

In addition to needing info Iliyan mentioned - what kernel are you running?
Is it a standard backport kernel?  Do you know if a kernel update coincides
with the performance degredation showing up?

Quoting Iliyan Stoyanov (ilf at ilf.me):
> Hi Ivan,
> 
> you should probably do a monitoring with iostat and vmstat also. On the
> top of my head I can think of at least 3 or 4 reasons why this might be
> happening. I have similar problems with a simple laptop machine without
> LXC containers on it (and don't have such on a server with a bunch of
> containers on it). In my experience with bad SI everything always come
> back to be RAM related. Also check your filesystem performance. Most of
> the FSes nowadays keep a ton of the journalling info in RAM. I know my
> response is not exactly an answer to your specific question but I hope
> it might give you some pointers for better monitoring of the situation.
> 
> BR,
> 
> --ilf
> 
> On Thu, 2011-09-15 at 09:12 -0600, Ivan Fetch wrote:
> 
> > Hello,
> > 
> > I've inherited a Sun 4540 (thumper) machine running 9 LXC containers. During the past few weeks we've been troubleshooting a decline in performance, which ends up in high %SI (software interrupt) CPU usage. I'm hoping someone here can help troubleshoot and narrow down what the real issue is - this one really has me stumped.
> > 
> > THis box has 48 disks, 5 RAID6 which are in a RAID0, using md. Two NICs are bonded together, and a bridge is used for the box's IP, and the LXC network interfaces.
> > 
> > Linux is Ubuntu 10.04, LXC 0.6.3 , containers are also 10.04. Containers run Apache, some custom image processing, gaussian, and FTP server...
> > 
> > The box performs well after a reboot, with all containers back online. After ~5 days, we notice that the box is sluggish, and backup jobs (Netbackup) get less than 1Mb/sec over the network. CPU eventually reaches 61% SI. OTher processes (I am looking at ps -ax -o pcpu ..... |sort -n) begin taking much higher percent CPU than they should need, I imagine because the high %SI is taking cycles; E.G. I'll briefly see ps or sort or a shell using 6% CPU. Top shows %sy between 5-20, %wa under 5.
> > Memory (32Gb) is mostly used for cache, and there is no swapping.
> > 
> > I know next-to-nothing about tracking down the cause for high %SI CPU usage.
> > 
> > 
> > Thanks for any help looking at this with a clear head,
> > 
> > - Ivan
> > 
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> > .
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> ------------------------------------------------------------------------------
> Doing More with Less: The Next Generation Virtual Desktop 
> What are the key obstacles that have prevented many mid-market businesses
> from deploying virtual desktops?   How do next-generation virtual desktops
> provide companies an easier-to-deploy, easier-to-manage and more affordable
> virtual desktop model.http://www.accelacomm.com/jaw/sfnl/114/51426474/

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