> In either of these situations, one glusterfsd process on whatever peer the > client is currently talking to will skyrocket to *nproc* cpu usage (800%, > 1600%) and the storage cluster is essentially useless; all other clients > will eventually try to read or write data to the overloaded peer and, when > that happens, their connection will hang. Heals between peers hang because > the load on the peer is around 1.5x the number of cores or more. This occurs > in either gluster 3.6 or 3.7, is very repeatable, and happens much too > frequently. I have some good news and some bad news. The good news is that features to address this are already planned for the 4.0 release. Primarily I'm referring to QoS enhancements, some parts of which were already implemented for the bitrot daemon. I'm still working out the exact requirements for this as a general facility, though. You can help! :) Also, some of the work on "brick multiplexing" (multiple bricks within one glusterfsd process) should help to prevent the thrashing that causes a complete freeze-up. Now for the bad news. Did I mention that these are 4.0 features? 4.0 is not near term, and not getting any nearer as other features and releases keep "jumping the queue" to absorb all of the resources we need for 4.0 to happen. Not that I'm bitter or anything. ;) To address your more immediate concerns, I think we need to consider more modest changes that can be completed in more modest time. For example: * The load should *never* get to 1.5x the number of cores. Perhaps we could tweak the thread-scaling code in io-threads and epoll to check system load and not scale up (or even scale down) if system load is already high. * We might be able to tweak io-threads (which already runs on the bricks and already has a global queue) to schedule requests in a fairer way across clients. Right now it executes them in the same order that they were read from the network. That tends to be a bit "unfair" and that should be fixed in the network code, but that's a much harder task. These are only weak approximations of what we really should be doing, and will be doing in the long term, but (without making any promises) they might be sufficient and achievable in the near term. Thoughts? _______________________________________________ Gluster-devel mailing list Gluster-devel@xxxxxxxxxxx http://www.gluster.org/mailman/listinfo/gluster-devel
