Mailinglist Archive: opensuse (1256 mails)

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Re: [opensuse] Is 40 dropped packets out of 300,000 high? This is wired cat5 LAN.
  • From: Per Jessen <per@xxxxxxxxxxxx>
  • Date: Fri, 02 Jun 2017 07:46:56 +0200
  • Message-id: <ogqu4g$cjg$4@saturn.local.net>
Carlos E. R. wrote:

On 2017-06-01 14:22, Per Jessen wrote:
Carlos E. R. wrote:

On 2017-06-01 08:31, Per Jessen wrote:

Some more examples -

on machines with uptimes between 30 and 60 days, depending on their
load, I see drop rates of up to 1%. 0.99% on a xen guest, fairly
busy.

On a mirror+squid, uptime 45days, I see 7% drop on one interface.

On four xen guests, not the most potent host machine, each has
10-11% dropped rx packages ...

two webservers, uptime 1600 days and 92 days, 0 rx drops.

The only possible pattern here might be the xen guests which
exhibit
somewhat higher rates than physical machines. My guess is that a
machine dropping packages is simply busy - too much incoming
traffic or too busy to process the interrupts.

Question.

The network "hardware" in the xen guest, is real or emulated?

They're virtual network devices, bridged with the physical device.

Because if it is emulated or virtual, not real hardware, it depends
on the host CPU having time to attend it at the precise instant it
is
needed. A real network card will have some internal memory and
processing power, and probably interrupts the machine only when the
data chunk is ready. Perhaps even moves the chunk to main ram via
dma, thus no cpu load.

The physical card still works the way it always has, but there is
obvioulsy more code to be executed to get a network interrupt
serviced
in a guest. Something like that.

I have to wonder at how/if the card can write to ram that belongs to
the guest. :-? :-o

It can't and it doesn't. At that level, the Dom0 (xen host) is in
charge. In this case, the dom0 has been up for 140days, and shows a
drop rate of 0.004%. The packages are dropped in the guests. I am
sure I could reduce the drop rate by running just one guest for
instance, but I need four to emulate a production setup.


--
Per Jessen, Zürich (18.9°C)
http://www.cloudsuisse.com/ - your owncloud, hosted in Switzerland.


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