On 9 August 2012 11:56, Ben Pfaff <b...@nicira.com> wrote: > I'm curious about the performance improvement. You mentioned a 10x > performance improvement. How much did CPU usage increase as part of > that? We already have users who complain when CPU usage spikes to 100%; > I'm not sure that users will be happy if CPU usage can spike to 1000% > (!).
Giuseppe did that basic benchmarking on Linux with the threaded userspace patch and may have observed CPU usage statistics during that work. I don't have current numbers on the FreeBSD port, but will get some soon. Performance improvements are very important on FreeBSD of course because we have only the userspace datapath. > Oh I see, it looks like there is only one thread that does all packet > processing? I had a notion that there would be many threads, for > example on a per-datapath or per-port basis. It's very impressive > getting 10x improvement with only a single additional thread. Eventually I think a thread per datapath may be the way to go, and I think the model in this patch can be reasonably extended to per-datapath. > I looked at the repository and then at the diff, both very briefly. The > repository looks more like development notes than something mergeable; > the diff was easier to read. Yes, the repo started from a snapshot patch against 1.1.0pre2 and has evolved over time. To get to something mergeable I'd expect to roll it all up, or refactor into two or three committable pieces. > One early reaction to the code is that there are too many #ifdefs > (mainly for locking and unlocking mutexes). I think that we should be > able to remove many of them with a few well-chosen macros. Indeed; the original 1.1.0pre2 work included this: /* We could use these macros instead of using #ifdef and #endif every time we * need to call the pthread_mutex_lock/unlock. #ifdef THREADED #define LOCK(mutex) pthread_mutex_lock(mutuex) #define UNLOCK(mutex) pthread_mutex_unlock(mutex) #else #define LOCK(mutex) #define UNLOCK(mutex) #endif but then never used those macros. I can switch it over to this scheme if this is an agreeable approach (or define macros for each individual lock, e.g. TABLE_LOCK and PORT_LOCK). > OVS recently got a library, lib/worker.c, for implementing code in a > "worker process". So far, we're using that in a single-worker-process > model, mostly for asynchronous logging, but we could generalize it so > that there could be a second worker process used for datapath > implementation. If this would achieve acceptable performance, then it > would avoid the difficulties of threads. I guess the question there is > how much communication a process model would require versus a thread > model. Right now packets that had a flow lookup miss are the only data flowing from the datapath thread to the main thread, so that should be easily done in either a thread or process model. In the other direction the datapath thread needs access to the flow table and I think this would be a bit more awkward to implement in a process model. (On the other hand, a userland datapath process may be a decent analogue to the Linux kernel module.) -Ed _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
