Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.debian.kernel > #60073

Bug#888465: CPU usage reporting issues

Cross-posted to 2 groups.

Show all headers | View raw

(cleaned the post up for readability, sorry about that)

On 01/25/2018 05:40 PM, Hans van Kranenburg wrote:
> This means that your vcpus want to execute work but are not being
> scheduled on a physical cpu core. Either the physical machine gets too
> much work from all the virtual machines that are requesting cpu time, or
> other things are going on, like your virtual machine getting paused
> (e.g. when doing live migration there's a handover moment when it's
> shortly paused and then resumed, this is also visible as a short 100%
> steal spike).

After going over log files, it appears that the issue started when 
Amazon did a live migration of the VM, probably for the Meltdown patching.

> A patch to fix that cpu accounting breakage (picked from linux 4.15) was
> included in 4.9.65-3. So only for the 4.9.0-3 (which actual version?)
> you could be seeing that one happening.

The versions were both 4.9.30-2+deb9u2 and the latest, 4.9.65-3+deb9u2.  
So basically the kernel never recovered properly after being paused 
during a live migration.

> Because of the mentioned steal time fix that was included in a version
> in between the 2 versions you mention, my first suggestion would be to
> see if the symptoms on the old and new kernel are exactly the same, or
> if they are only similar but different.
>
> Hans

I already rebooted the system running the 4.9.65 kernel, and beforehand, 
the symptoms were the same.  The CPU usage stats went back to normal 
after the reboot.

-- 
Ryan Thoryk
ryan@thoryk.com
ryan@tliquest.net

Back to linux.debian.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Bug#888465: CPU usage reporting issues Ryan Thoryk <ryan@thoryk.com> - 2018-01-26 00:30 +0100
  Bug#888465: Additional example Ryan Thoryk <ryan@thoryk.com> - 2018-01-26 00:50 +0100
  Bug#888465: CPU usage reporting issues Hans van Kranenburg <hans@knorrie.org> - 2018-01-26 01:00 +0100
    Bug#888465: CPU usage reporting issues Ryan Thoryk <ryan@thoryk.com> - 2018-01-26 01:20 +0100
    Bug#888465: CPU usage reporting issues Ryan Thoryk <ryan@thoryk.com> - 2018-01-26 01:20 +0100

csiph-web