[ovs-build] Broken: ovsrobot/ovs#3525 (series_228959 - 8d4b0c0)

[Travis CI]

Build Update for ovsrobot/ovs
-------------------------------------

Build: #3525
Status: Broken

Duration: 20 mins and 12 secs
Commit: 8d4b0c0 (series_228959)
Author: Gaetan Rivet
Message: dpif-netdev: Use lockless queue to manage offloads

The dataplane threads (PMDs) send offloading commands to a dedicated
offload management thread. The current implementation uses a lock
and benchmarks show a high contention on the queue in some cases.

With high-contention, the mutex will more often lead to the locking
thread yielding in wait, using a syscall. This should be avoided in
a userland dataplane.

The mpsc-queue can be used instead. It uses less cycles and has
lower latency. Benchmarks show better behavior as multiple
revalidators and one or multiple PMDs writes to a single queue
while another thread polls it.

One trade-off with the new scheme however is to be forced to poll
the queue from the offload thread. Without mutex, a cond_wait
cannot be used for signaling. The offload thread is implementing
an exponential backoff and will sleep in short increments when no
data is available. This makes the thread yield, at the price of
some latency to manage offloads after an inactivity period.

Signed-off-by: Gaetan Rivet <grive at u256.net>
Reviewed-by: Eli Britstein <elibr at nvidia.com>
Signed-off-by: 0-day Robot <robot at bytheb.org>

View the changeset: https://github.com/ovsrobot/ovs/compare/93f0699340e3...8d4b0c071374

View the full build log and details: https://travis-ci.com/github/ovsrobot/ovs/builds/216707774?utm_medium=notification&utm_source=email


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