Re: ipvs_syncmaster brings cpu to 100%

[trimmed Cc to avoid spamming...]

Ok, just to summarize the long thread from the beginning:

The goal: setting up a Local Director with IPVS with state
synchronization, failover and failback.

The hardware: 1 CPU Intel Xeon 3,4 Ghz - HP DL380G4 on 2 identical boxes

The problems (please note that all kernel versions are *Debian* kernels):
1. Kernel 2.6.8: got a system lock of the standby node when simulating
a failover. The load average as reported from "top" or "w" is always
0.00.

2. Kernel 2.6.11 and Kernel 2.6.12: failover and failback works fine,
but the load average as reported from "top" or "w" is always
systematically at 2.00 or more with both sync thread started
(ipvs_syncmaster and ipvs_syncbackup). Load average from top is 1.00
or mroe with only one thread (i.e. ipvs_syncmaster). Horms reported
that he was not able to reproduce this on a non-Xeon system.

That's all, let me know if you need more info.
Regards,
Luca


On 26/09/05, Nishanth Aravamudan [off-list ref] wrote:

On 26.09.2005 [15:52:02 +0200], Luca Maranzano wrote:

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On 26/09/05, Nishanth Aravamudan [off-list ref] wrote:

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On 26.09.2005 [17:12:32 +0900], Horms wrote:

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On Mon, Sep 26, 2005 at 05:05:10PM +0900, Horms wrote:

[snip]

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Furthermore, if I make an "rgrep" in the source tree of kernel 2.6.12
the function schedule_timeout() is more used than the ssleep() (517
occurrencies vs. 43), so why in ip_vs_sync.c there was this change?

The other oddity is that Horms reported on this list that on non Xeon
CPU the same version of kernel of mine does not present the problem.

I'm getting crazy :-)

I've prepared a patch, which reverts the change which was introduced
by Nishanth Aravamudan in February.

Was the 100% cpu utilization only occurring on Xeon processors?

That seems to be the only case where were this problem has been
observed. I don't have such a processor myself, so I haven't actually
been able to produce the problem locally.

One reason I posted this issue to netdev was to get some more
eyes on the problem as it is puzzling to say the least.

quoted

Care to try to use msleep_interruptible() instead of ssleep(), as
opposed to schedule_timeout()?

I will send a version that does that shortly, Luca, can
you plase check that too?

Here is that version of the patch. Nishanth, I take it that I do not
need to set TASK_INTERRUPTABLE before calling msleep_interruptible(),
please let me know if I am wrong.

Yes, exactly. I'm just trying to narrow it down to see if it's the task
state that's causing the issue (which, to be honest, doesn't make a lot
of sense to me -- with ssleep() your load average will go up as the task
will be UNINTERRUPTIBLE state, but I am not sure why utilisation would
rise, as you are still sleeping...)

[trimmed lvs-users from my reply, as it is a closed list]

quoted

Just to add more info, please note the output of "ps":

debld1:~# ps aux|grep ipvs
root      3748  0.0  0.0      0     0 ?        D    12:09   0:00
[ipvs_syncmaster]
root      3757  0.0  0.0      0     0 ?        D    12:09   0:00
[ipvs_syncbackup]

Note the D status, i.e. (from ps(1) man page): Uninterruptible sleep
(usually IO)

The msleep_interruptible() change should fix that.

But that does not show 100% CPU utilisation at all, it shows 0. Did you
mean to say your load increases?

I'm still unclear what the problem is. Horms initial Cc trimmed some
important information. It would be very useful to "start over" -- at
least from the perspective of what the problem actually is.

quoted

I hope to have a Xeon machine to make some more tests in the next
days, in the mean time I'll try to reproduce my setup on a couple of
VMWare Workstation machines.

Please don't top-most. It makes it really hard to write sane replies...

Thanks,
Nish