Performance Manager 2/12/07 This document will describe an architecture and a phased plan for an OpenFabrics OpenIB performance manager. Currently, there is no open source performance manager, only a perfquery diagnostic tool which some have scripted into a "poor man's" performance manager. The primary responsibilities of the performance manager are to: 1. Monitor subnet topology 2. Based on subnet topology, monitor performance and error counters. Also, possible counters related to congestion. 3. Perform data reduction (various calculations (rates, histograms, etc.)) on counters obtained 4. Log performance data and indicate "interesting" related events Performance Manager Components 1. Determine subnet topology Performance manager can determine the subnet topology by subscribing for GID in and out of service events. Upon receipt of a GID in service event, use GID to query SA for corresponding LID by using SubnAdmGet NodeRecord with PortGUID specified. It would utilize the LID and NumPorts returned and add this to the monitoring list. Note that the monitoring list can be extended to be distributed with the manager "balancing" the assignments of new GIDs to the set of known monitors. For GID out of service events, the GID is removed from the monitoring list. 2. Monitoring Counters to be monitored include performance counters (data octets and packets both receive and transmit) and error counters. These are all in the mandatory PortCounters attribute. Future support will include the optional 64 bit counters, PortExtendedCounters (as this is only known to be supported on one IB device currently). Also, one congestion counter (PortXmitWait) will also be monitored (on switch ports) initially. Polling rather than sampling will be used as the monitoring technique. The polling rate configurable from 1-65535 seconds (default TBD) Note that with 32 bit counters, on 4x SDR links, byte counts can max out in 16 seconds and on 4x DDR links in 8 seconds. The polling rate needs to deal with this is accurate byte and packet rates are desired. Since IB counters are sticky, the counters need to be reset when they get "close" to max'ing out. This will result in some inaccuracy. When counters are reset, the time of the reset will be tracked in the monitor and will be queryable. Note that when the 64 bit counters are supported more generally, the polling rate can be reduced. The performance manager will support parallel queries. The level of parallelism is configurable with a default of 64 queries outstanding at one time. Configuration and dynamic adjustment of any performance manager "knobs" will be supported. Also, there will be a console interface to obtain performance data. It will be able to reset counters, report on specific nodes or node types of interest (CAs only, switches only, all, ...). The specifics are TBD. 3. Data Reduction For errors, rate rather than raw value will be calculated. Error event is only indicated when rate exceeds a threshold. For packet and byte counters, small changes will be aggregated and only significant changes are updated. Aggregated histograms (per node, all nodes (this is TBD))) for each counter will be provided. Actual counters will also be written to files. NodeGUID will be used to identify node. File formats are TBD. One format to be supported might be CSV. 4. Logging "Interesting" events determined by the performance manager will be logged as well as the performance data itself. Significant events will be logged to syslog. There are some interesting scalability issues relative to logging especially for the distributed model. Events will be based on rates which are configured as thresholds. There will be configurable thresholds for the error counters with reasonable defaults. Correlation of PerfManager and SM events is interesting but not a mandatory requirement. Performance Manager Scalability Clearly as the polling rate goes up, the number of nodes which can be monitored from a single performance management node decreases. There is some evidence that a single dedicated management node may not be able to monitor the largest clusters at a rapid rate. There are numerous PerfManager models which can be supported: 1. Integrated as thread(s) with OpenSM (run only when SM is master) 2. Standby SM 3. Standalone PerfManager (not running with master or standby SM) 4. Distributed PerfManager (most scalable approach) Note that these models are in order of implementation complexity and hence "schedule". The simplest model is to run the PerfManager with the master SM. This has the least scalability but is the simplest model. Note that in this model the topology can be obtained without the GID in and out of service events but this is needed for any of the other models to be supported. The next model is to run the PerfManager with a standby SM. Standbys are not doing much currently (polling the master) so there is much idle CPU. The downside of this approach is that if the standby takes over as master, the PerfManager would need to be moved (or is becomes model 1). A totally separate standlone PerfManager would allow for a deployment model which eliminates the downside of model 2 (standby SM). It could still be built in a similar manner with model 2 with unneeded functions (SM and SA) not included. The advantage of this model is that it could be more readily usable with a vendor specific SM (switch based or otherwise). Vendor specific SMs usually come with a built-in performance manager and this assumes that there would be a way to disable that performance manager. Model 2 can act like model 3 if a disable SM feature is supported in OpenSM (command line/console). This will take the SM to not active. The most scalable model is a distributed PerfManager. One approach to distribution is a hierarchial model where there is a PerfManager at the top level with a number of PerfMonitors which are responsible for some portion of the subnet. The separation of PerfManager from OpenSM brings up the following additional issues: 1. What communication is needed between OpenSM and the PerfManager ? 2. Integration of interesting events with OpenSM log (Does performance manager assume OpenSM ? Does it need to work with vendor SMs ?) Hierarchial distribution brings up some additional issues: 1. How is the hierarchy determined ? 2. How do the PerfManager and PerfMonitors find each other ? 3. How is the subnet divided amongst the PerfMonitors 4. Communication amongst the PerfManager and the PerfMonitors (including communication failures) In terms of inter manager communication, there seem to be several choices: 1. Use vendor specific MADs (which can be RMPP'd) and build on top of this 2. Use RC QP communication and build on top of this 3. Use IPoIB which is much more powerful as sockets can then be utilized RC QP communication improves on the lower performance of the vendor specific MAD approach but is not as powerful as the socket based approach. The only downside of IPoIB is that it requires multicast to be functioning. It seems reasonable to require IPoIB across the management nodes. This can either be a separate IPoIB subnet or a shared one with other endnodes on the subnet. (If this communication is built on top of sockets, it can be any IP subnet amongst the manager nodes). The first implementation phase will address models 1-3. Model 3 is optional as it is similar to models 1 and 2 and may be not be needed. Model 4 will be addressed in a subsequent implementation phase (and a future version of this document). Model 4 can be built on the basis of models 1 and 2 where some SM, not necessarily master, is the PerfManager and the rest are PerfMonitors. Performance Manager Partition Membership Note that as the performance manager needs to talk via GSI to the PMAs in all the end nodes and GSI utilizes PKey sharing, partition membership if invoked must account for this. The most straightforward deployment of the performance manager is to have it be a member of the full default partition (P_Key 0xFFFF). Performance Manager Redundancy TBD (future version of this document) Congestion Management TBD (future version of this document) QoS Management TBD (future version of this document)