On Nov 8, 2012, at 10:00 AM, Scott Atchley <[email protected]> wrote:
> On Nov 8, 2012, at 9:39 AM, Mark Nelson <[email protected]> wrote: > >> On 11/08/2012 07:55 AM, Atchley, Scott wrote: >>> On Nov 8, 2012, at 3:22 AM, Gandalf Corvotempesta >>> <[email protected]> wrote: >>> >>>> 2012/11/8 Mark Nelson <[email protected]>: >>>>> I haven't done much with IPoIB (just RDMA), but my understanding is that >>>>> it >>>>> tends to top out at like 15Gb/s. Some others on this mailing list can >>>>> probably speak more authoritatively. Even with RDMA you are going to top >>>>> out at around 3.1-3.2GB/s. >>>> >>>> 15Gb/s is still faster than 10Gbe >>>> But this speed limit seems to be kernel-related and should be the same >>>> even in a 10Gbe environment, or not? >>> >>> We have a test cluster with Mellanox QDR HCAs (i.e. NICs). When using Verbs >>> (the native IB API), I see ~27 Gb/s between two hosts. When running Sockets >>> over these devices using IPoIB, I see 13-22 Gb/s depending on whether I use >>> interrupt affinity and process binding. >>> >>> For our Ceph testing, we will set the affinity of two of the mlx4 interrupt >>> handlers to cores 0 and 1 and we will not using process binding. For single >>> stream Netperf, we do use process binding and bind it to the same core >>> (i.e. 0) and we see ~22 Gb/s. For multiple, concurrent Netperf runs, we do >>> not use process binding but we still see ~22 Gb/s. >> >> Scott, this is very interesting! Does setting the interrupt affinity >> make the biggest difference then when you have concurrent netperf >> processes going? For some reason I thought that setting interrupt >> affinity wasn't even guaranteed in linux any more, but this is just some >> half-remembered recollection from a year or two ago. > > We are using RHEL6 with a 3.5.1 kernel. I tested single stream Netperf with > and without affinity: > > Default (irqbalance running) 12.8 Gb/s > IRQ balance off 13.0 Gb/s > Set IRQ affinity to socket 0 17.3 Gb/s # using the Mellanox script > > When I set the affinity to cores 0-1 _and_ I bind Netperf to core 0, I get > ~22 Gb/s for a single stream. Note, I used hwloc to determine which socket was closer to the mlx4 device on our dual socket machines. On these nodes, hwloc reported that both sockets were equally close, but a colleague has machines where one socket is closer than the other. In that case, bind to the closer socket (or to cores within the closer socket). > >>> We used all of the Mellanox tuning recommendations for IPoIB available in >>> their tuning pdf: >>> >>> http://www.mellanox.com/related-docs/prod_software/Performance_Tuning_Guide_for_Mellanox_Network_Adapters.pdf >>> >>> We looked at their interrupt affinity setting scripts and then wrote our >>> own. >>> >>> Our testing is with IPoIB in "connected" mode, not "datagram" mode. >>> Connected mode is less scalable, but currently I only get ~3 Gb/s with >>> datagram mode. Mellanox claims that we should get identical performance >>> with both modes and we are looking into it. >>> >>> We are getting a new test cluster with FDR HCAs and I will look into those >>> as well. >> >> Nice! At some point I'll probably try to justify getting some FDR cards >> in house. I'd definitely like to hear how FDR ends up working for you. > > I'll post the numbers when I get access after they are set up. > > Scott > -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
