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Re: [Xen-users] Serious performance problems - is Xen not ready for prod

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Serious performance problems - is Xen not ready for production use?
From: Patrick Hess <posi@xxxxxxx>
Date: Thu, 14 Jul 2005 17:38:46 +0200
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Hello again,

I just had some time to check some more things...

If that doesn't help:
* what sort of workload are you imposing in your tests?

I just used thunderbird to access my IMAP folders and used a single browser to access squirrel webmail (also using same IMAP).

* do you know where the CPU time is going in the domain?

No idea :) An "xm list" on the dom0 didn't showed much seconds for the "slow" machine as I expected when I saw this load avg.

* does the output of top and vmstat look weird?

Yes :) See below...

* anything strange in the dmesg output (try comparing to the dmesg from a native boot)?

No, that seems to be fine.
vmstat does not work:

root@pbone:~# vmstat
Unknown HZ value! (39) Assume 100.
procs memory swap io system cpu r b w swpd free buff cache si so bi bo in cs us sy id
Segmentation fault

...and top looks like this after a minute running all services:

 19:25:10 up 1 day,  6:10,  1 user,  load average: 14.41, 5.82, 2.75
137 processes: 135 sleeping, 2 running, 0 zombie, 0 stopped
CPU states:   0.8% user,  99.2% system,   0.0% nice,   0.0% idle
Mem:    257488K total,   255368K used,     2120K free,      128K buffers
Swap:        0K total,        0K used,        0K free,     2440K cached
  PID USER     PRI  NI  SIZE  RSS SHARE STAT %CPU %MEM   TIME COMMAND
 2567 list      18   0  3716 1004    72 D     0.3  0.3   0:00 python
 2582 root      18   0  1824  400   144 R     0.3  0.1   0:00 top
 2567 list      18   0  3664 1284   392 D     0.4  0.4   0:00 python
    8 root      15   0     0    0     0 DW    0.2  0.0   0:00 kswapd0
 2576 root      18   0 87092 5520   324 D     0.2  2.1   0:00 apache
 2577 root      18   0 87092 5520   324 D     0.2  2.1   0:00 apache
 2578 root      18   0 87092 5520   324 D     0.2  2.1   0:00 apache
 2580 root      18   0 87092 5520   324 D     0.2  2.1   0:00 apache
 2583 root      17   0  1760  656   524 D     0.2  0.2   0:00 cron


When I had a closer look to the mem line:
Mem:    257488K total,   255368K used,     2120K free,      128K buffers

...it looked strange to me. I checked and found my config file for this domain looking like this:

...
memory = 128
extra = "mem=268435456"
...

This was left over from my tries to get the "xm balloon" working. I removed the extra line from the config file - and voila, it works... Is this config above wrong at all or is the strange behaviour I found related to the bugs with balloon feature..?

Regards,
  Patrick

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