[lvs-users] Kernel Tuning for LVS

Simon Horman horms at verge.net.au
Sat Aug 7 00:42:30 BST 2010

On Fri, Aug 06, 2010 at 02:16:25PM -0400, Neal B wrote:
> Hello,
> Over the past day I have been searching the net for the definitive answer
> for the recommended tweaks to the kernel for ipvs.  If you are doing this
> then change this, but that does not exist.  :)
> I see suggestions on the net for changing all of the following:
> /proc/sys/net/core/wmem_max
> /proc/sys/net/core/wmem_default
> /proc/sys/net/core/rmem_max
> /proc/sys/net/core/rmem_default
> /proc/sys/fs/filemax
> /proc/sys/net/ipv4/tcp_tw_recycle
> /proc/sys/net/ipv4/tcp_tw_reuse
> /proc/sys/net/ipv4/tcp_max_tw_buckets
> /proc/sys/net/ipv4/tcp_fin_timeout
> /proc/sys/net/ipv4/tcp_max_syn_backlog
> /proc/sys/net/ipv4/tcp_syncookies
> /proc/sys/net/ipv4/ip_local_port_range
> /proc/sys/net/core/netdev_max_backlog
> I assume that these values are very specific to the desired goal your load
> balancer is trying to achieve.
> I am currently seeing on our lvs active/passive pair a drop in connections
> every 10 minutes undder high load.  Turning off the ipvs_sync daemon caused
> this 10 minute spikes in failures to disappear.  The 10 min spike in
> failures is gone however now failures seem to be following the number of
> connections.  High connection = Higher error.  We have a full GIGE internet
> connection and pass TBs of traffic per day in an LVS-NAT setup.  Changing
> the magic parameter above in the kernel is going to increase the maximum
> allowed connections.
> We do see this error:
> IPVS: ip_vs_send_async error
> Checking out prior posts this will help and we can implement:
> http://www.mail-archive.com/lvs-users@linuxvirtualserver.org/msg04479.html
> Can a few experts on this list suggest which of the values above to target
> tuning first?

Hi Neal,

I don't have an answer for that question. But I am interested in
changing ip_vs_sync.c such that it uses a dynamic "sleep" to avoid
this problem from that end.

Out of interest, which kernel are you using, and more specifically,
what is the argument to msleep_interruptible() in ip_vs_sync.c ?
What I am interested to know is if you are seeing the error with

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