[ovs-dev] [PATCH v8] dpif-netlink: distribute polling to discreet handlers
Flavio Leitner
fbl at sysclose.org
Thu Sep 10 13:23:06 UTC 2020
On Wed, Sep 09, 2020 at 06:08:21PM +0100, Mark Gray wrote:
> From: Aaron Conole <aconole at redhat.com>
>
> Currently, the channel handlers are polled globally. On some
> systems, this causes a thundering herd issue where multiple
> handler threads become active, only to do no work and immediately
> sleep.
>
> The approach here is to push the netlink socket channels to discreet
> handler threads to process, rather than polling on every thread.
> This will eliminate the need to wake multiple threads.
>
> To check:
>
> ip netns add left
> ip netns add right
> ip link add center-left type veth peer name left0 netns left
> ip link add center-right type veth peer name right0 netns right
> ip link set center-left up
> ip link set center-right up
> ip -n left ip link set left0 up
> ip -n left ip addr add 172.31.110.10/24 dev left0
> ip -n right ip link set right0 up
> ip -n right ip addr add 172.31.110.11/24 dev right0
>
> ovs-vsctl add-br br0
> ovs-vsctl add-port br0 center-right
> ovs-vsctl add-port br0 center-left
>
> # in one terminal
> perf record -e sched:sched_wakeup,irq:softirq_entry -ag
>
> # in a separate terminal
> ip netns exec left arping -I left0 -c 1 172.31.110.11
>
> # in the perf terminal after exiting
> perf script
>
> Look for the number of 'handler' threads which were made active.
>
> Suggested-by: Ben Pfaff <blp at ovn.org>
> Co-authored-by: Mark Gray <mark.d.gray at redhat.com>
> Reported-by: David Ahern <dsahern at gmail.com>
> Reported-at: https://mail.openvswitch.org/pipermail/ovs-dev/2019-December/365857.html
> Cc: Matteo Croce <technoboy85 at gmail.com>
> Cc: Flavio Leitner <fbl at sysclose.org>
> Fixes: 69c51582f ("dpif-netlink: don't allocate per thread netlink sockets")
> Signed-off-by: Aaron Conole <aconole at redhat.com>
> Signed-off-by: Mark Gray <mark.d.gray at redhat.com>
> ---
Acked-by: Flavio Leitner <fbl at sysclose.org>
Thanks Aaron and Mark!
fbl
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