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[lvs-users] Slow LVS NAT with Debian Squeeze 6.0.3 kernel >2.6.32-38

 

 

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ext.gfi.sebastien.rohaut at sncf

Dec 2, 2011, 4:50 AM

Post #1 of 2 (1675 views)
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[lvs-users] Slow LVS NAT with Debian Squeeze 6.0.3 kernel >2.6.32-38

Hi,



I'm encountering a real problem with lastest Debian squeeze kernel.



With 2.6.32-31 kernel (Debian Squeeze 6.0.2) all is working OK.



When upgrading to Debian 6.0.3, LVS NAT started to be very slow. A single html page, 4KB, takes about 10-15 seconds to display (immediate on 2.6.32-31).

We tried with 2.6.32-38 and lastest 2.6.32-39, we have the problem with both. We tried to upgrade only the kernel from 6.0.2, so we are sure this is related to the kernel.



If we access the real server directly, there's no problem, and his IP Gateway is on the load balancer, so the IP forwardind seems to work correctly on the server. We tried with keepalived 1.1.20 and 1.2.2, It seems it's not related to keepalived. So, It must be NAT from IPVS layer.



The only modified kernel values are ipv6 disabling (tried with and without, same problem), and ipv4 forwarding.



We recompiled ipvsadm-1.26 (1.25 by default on Debian), and recompiled keepalived 1.2.2 on the platform with correct kernel headers, rebooted, same problem.



Has someone the same problem?



Sebastien ROHAUT



Message initially posted on keepalived-devel list.



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benjamin.von.mossner at insparx

Apr 5, 2012, 1:27 AM

Post #2 of 2 (1338 views)
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Re: [lvs-users] Slow LVS NAT with Debian Squeeze 6.0.3 kernel >2.6.32-38 [In reply to]

Hi,

Might be a bit late, but should be noted.
We had the same issue on our Testsystem, after upgrading to Debian squeeze.
A posting on http://blog.gmane.org/gmane.comp.linux.lvs.user/month=20111101 from Michael Schwartzkopff gave the right hint and led to the solution.
Looks like starting some when after kernel 2.6.26, generic-segmentation-offload was introduced and activated by default - at least our NIC - driver: tg3 on Debian squeeze.

So disabling it via ethtool solved the problem.
[snip]
# ethtool -K eth0 gro off
# ethtool -k eth0 | fgrep 'generic-receive-offload'
generic-receive-offload: off
[snap]

Hope this helps.

Benjamin von Mossner


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