Re: [Xen-users] XEN 4.3.1 network performance issue

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Dec 27, 2013 at 05:00:16PM +0200, NiX wrote:
> > On Fri, Dec 27, 2013 at 02:17:19PM +0200, NiX wrote:
> >> > On Tue, Dec 24, 2013 at 05:06:37PM +0200, NiX wrote:
> >> >> Hi. I am running a XEN VM in PV mode. This VM has four cores enabled.
> >> VM
> >> >> network config is as follows:
> >> >>
> >> >> vif = ["ip=127.0.0.1,mac=XX:XX:XX:XX:XX:XX,bridge=br0,rate=100Mb/s"]
> >> >>
> >> >> Dom0 is dual XEON X5450 with 16GB of RAM.
> >> >>
> >> >> I can barely zmap at 10mbps ~ 12k packets/second on this VM
> >> >>
> >> >
> >> > My google-fu tells me that zmap sends out gigantic amount of TCP SYN
> >> > packets in its default configuration. It is possible the ring size
> >> > between frontend and backend is the bottleneck. Data copying from
> >> > frontend to backend might also be a problem.
> >> >
> >> > You can probably patch your Dom0 and DomU kernel with multi-page ring
> >> > support to see if it makes it better.
> >> >
> >> > Wei.
> >> >
> >>
> >> I was not able neither to exceed 10k packets/second with a lightweight
> >> equivalent software and netback/0 fully utilized one 3GHz core.
> >>
> >
> > Hmm... You're using kthread-based netback. In your use case frontend is
> > likely to create interrupt storm for backend. Do you have breakdown of
> > CPU usage (sy, si etc)?
> 
> I am using Linux nix 3.2.53-grsec #1 SMP and the server is pretty much
> idle expect when I attempt to zmap.Load average: 0.09 0.06 0.13
> 
> ps aux | grep netback
> root      1411  2.6  0.0      0     0 ?        S    Dec09 696:17 [netback/0]
> root      1412  0.0  0.0      0     0 ?        S    Dec09   2:44 [netback/1]
> root      1413  1.1  0.0      0     0 ?        S    Dec09 312:39 [netback/2]
> root      1414  0.0  0.0      0     0 ?        S    Dec09   0:00 [netback/3]
> root      1415  0.0  0.0      0     0 ?        S    Dec09   8:22 [netback/4]
> root      1416  0.0  0.0      0     0 ?        S    Dec09   2:54 [netback/5]
> root      1417  0.0  0.0      0     0 ?        S    Dec09   0:00 [netback/6]
> root      1418  0.0  0.0      0     0 ?        S    Dec09   0:00 [netback/7]
> 
> It seems to only fully utilize netback/0 when I attempt to zmap and takes
> one 3GHz core ... Maybe there's something to look at in terms of
> optimizing?
> 

That's expected, because only one netback thread is necessary to serve
that VIF.

Could you run 'top' then press 1 and copy the summary area in your
email?

It should look like this:

top - 15:49:09 up 27 days,  6:14, 16 users,  load average: 5.00, 5.02, 5.08
Tasks: 259 total,   2 running, 257 sleeping,   0 stopped,   0 zombie
%Cpu0  :  1.0 us,  1.3 sy, 97.7 ni,  0.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu1  :  0.0 us,  0.3 sy, 99.7 ni,  0.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu2  :  4.0 us, 53.5 sy, 42.5 ni,  0.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu3  :  1.7 us, 40.2 sy, 58.1 ni,  0.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem:   8132308 total,  7385188 used,   747120 free,   160348 buffers
KiB Swap:        0 total,        0 used,        0 free,  3283276 cached

  PID USER      PR  NI  VIRT  RES  SHR S  %CPU %MEM    TIME+  COMMAND
 3378 colord    20   0  284m 110m 2484 R  98.0  1.4  15502:29 colord-sane
25531 weil      20   0 24788 3268 1436 S   2.0  0.0 165:58.78 htop
22448 weil      20   0 1010m  97m  24m S   0.7  1.2   4:57.67 chrome

Wei.

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