Add a FAQ categorry "Performance Problems". So far the only entry addresses the issue with using a new kernel module with an older (pre-megaflows) userspace.
Signed-off-by: Jarno Rajahalme <[email protected]> --- FAQ | 24 ++++++++++++++++++++++++ NEWS | 5 +++++ 2 files changed, 29 insertions(+) diff --git a/FAQ b/FAQ index cd3241a..a085bec 100644 --- a/FAQ +++ b/FAQ @@ -468,6 +468,30 @@ A: Open vSwitch uses different kinds of flows for different purposes: regardless of the type. +Performance Problems +-------------------- + +Q: I just upgraded and I see a performance drop. Why? + +A: Sometimes support for new protocol fields is added to OVS. If a + new OVS kernel module is paired with an older (pre 1.11) OVS + userspace, there may be a preformance drop. In particular, when + the new fields concern existing and widely used protocols, old + implementations may face a drop in performance. Since OVS release + 1.11, which added kernel wildcarding, this should be less of an + issue, as any new fields not understood by the userspace remain + automatically wildcarded. + + For example, OVS release 2.1 added support for TCP flags matching. + Pairing a new OVS kernel module with OVS userspace without kernel + wildcarding, each TCP flags combination for each TCP connection + appears as a separate flow miss for the OVS userspace, multiplying + the required flow setups in most (TCP-heavy) workloads. + + Upgrading the OVS userspace components will resolve these + performance issues. + + Configuration Problems ---------------------- diff --git a/NEWS b/NEWS index 43a2079..09c2fda 100644 --- a/NEWS +++ b/NEWS @@ -1,5 +1,10 @@ Post-v2.0.0 --------------------- + - TCP flags matching: OVS now supports matching of TCP flags. This + has an adverse performance impact when using OVS userspace older + than 1.11 (i.e., the ones without megaflows support) together + with a new OVS kernel module. It is recommended that the kernel + and userspace modules both are upgraded at the same time. - The default OpenFlow and OVSDB ports will change to IANA-assigned numbers in a future release. Consider updating your installations to specify port numbers instead of using the -- 1.7.10.4 _______________________________________________ dev mailing list [email protected] http://openvswitch.org/mailman/listinfo/dev
