-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Hi Joe
On 16/04/15 22:44, Joe Stringer wrote: > I had a lengthy discussion with someone in IRC last night who > observed some odd behaviour in OVS-2.3 userspace + module from > Linux-3.16. It seems like if OVS >= 2.3 is paired with OVS module > from Linux <= 3.16, then only one handler thread will handle > traffic even if multiple such threads exist. This limits the > performance of OVS particularly under high load. > > Prior to OVS-2.3 we had a dispatcher thread which distributed the > misses to multiple handler threads, but in 2.3 we shifted the > equivalent logic into the kernel. I understand that the requisite > patch for this functionality was merged in Linux-3.17: > https://github.com/torvalds/linux/commit/5cd667b0a4567048bb555927d6ee5 64f4e5620a9 > > For the most part, I don't think this is an issue because major > distros haven't shipped OVS-2.3 yet. Hopefully by the time they do > they will have recent kernels or will recommend dkms module. For > instance, Ubuntu 15.04 looks like it will have Linux-3.19. Using > the OVS module from this version should not exhibit this problem. Well that's good news.... > My main concern is whether this issue has been raised in OpenStack, > as it appears that the Kilo release (imminent) is expected to run > against Ubuntu 14.04, but there is no updated kernel or newer OVS > kernel module in Ubuntu Cloud Archive (launchpad summary of > packages below). If Ubuntu 14.04.3 hardware enablement stack is > required then this issue should not be present [as it would > presumably use the 15.04 kernel]. If an openvswitch-datapath-dkms > package for OVS-2.3 is distributed with the Ubuntu Cloud Archive, > then users can be recommended to use the dkms module. If users run > on a single-core machine, there'll be no problem ;-) Obviously not such good news; the 3.19 kernel will be made available on 14.04 - but not for a few weeks yet - and we intentionally dropped the dkms package in 2.3.x of ovs in Ubuntu - and we're backporting 2.3.1 as part of the OpenStack kilo cloud archive. > https://launchpad.net/~ubuntu-cloud-archive/+archive/ubuntu/kilo-stagi ng > > I reproduced this today using Ubuntu Cloud Archive paired with > Ubuntu 14.10, but it is equally applicable to Ubuntu 14.04 LTS. > > Steps to reproduce: - Install Ubuntu 14.04.2 - Add ubuntu cloud > archive for OpenStack Kilo[url below] - Install openvswitch-switch > - Add bridge, interface - ovs-vsctl set Open_vSwitch . > n-handler-threads 3 - ovs-appctl upcall/disable-megaflows (To > produce lots of misses) - hping3 --flood - Observe that only one > handler thread handles misses > > http://lists.openstack.org/pipermail/openstack-dev/2015-January/054820 .html > > Are there some OpenStack people out there that could clarify > whether this is a problem and if it's being addressed? Thanks for raising this potential issue; there is not a huge amount I can do between now and release of the Kilo Cloud Archive (Final Freeze is today), but if this does present a problem we can look into some potential stable updates to help resolve any performance impacts. Regards James - -- James Page Ubuntu and Debian Developer [email protected] [email protected] -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJVMDBIAAoJEL/srsug59jDG+8QAJAbefCIOEGGbwlxax+Fm2cg hNZTvQ8gMoIddxYB+GHsqjE4SpLuTghkq2dP9OJ1qkdOTCbZyU2+j2Qy/o0YBLps 2FWGoJhPCjk6P/1x946PqkLrp739Roe3ztoeit2dx2pb1fbNObInSQroyU+O/0AW 6TobFM6iJgTXC1aHE1Gww+WzSreL2mfiiPlsgBdqJ49ojDprDMV24U82iGonpWJ6 297/1anqPTSVG950JyYifV2zD5FrZjYLBHIOMfhAVjGQaZUzIZUYP3ay1ZSSj7LN 2HoTStXZ2cQIuCvxRe9DHdmqiCuYBbDSusxEduERZsggQ7VzRQCuft/BPLtyDqaQ qS25rnYvk2BHFLwhjEjKjQrO2CT7z2P9FGKA4ZESnIaa0HR49m7ZIIjfOqmB5Oms D/dO/cQr4Y66/wyyTNSL8gJqGWqCUL7cvd5HJo5fFDHWKoTy2G0pQcX5M5ql8ZFu k/CYd7YHdY5ABEJeki3Jbv6K7fqFijFWyDdKFiYu+xAsX248IJKZKmTwb7+mw/Rw lpSnAjoF/AN3kKRGWGA5hKqEVxq7lUsGe9jKsSmo6V3l/bUAPZh3v9yzMRbZlg8v 1pyn6xNv4kIzkYiJ/Xq29z68AaQJgsrHdUrKMHBWs5LCPKZ+K+mkAB+kNPebQzEa spfidrhOIEUT2HQ5I/YT =0FqP -----END PGP SIGNATURE----- _______________________________________________ discuss mailing list [email protected] http://openvswitch.org/mailman/listinfo/discuss
