Open MPI logo

Open MPI User's Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Open MPI User's mailing list

Subject: Re: [OMPI users] Infiniband performance Problem and stalling
From: Randolph Pullen (randolph_pullen_at_[hidden])
Date: 2012-09-07 01:27:19


One system is actually an i5-2400 - maybe its throttling back on 2 cores to save power? The other(I7) shows consistent CPU MHz on all cores ________________________________ From: Yevgeny Kliteynik <kliteyn_at_[hidden]> To: Randolph Pullen <randolph_pullen_at_[hidden]>; OpenMPI Users <users_at_[hidden]> Sent: Thursday, 6 September 2012 6:03 PM Subject: Re: [OMPI users] Infiniband performance Problem and stalling On 9/3/2012 4:14 AM, Randolph Pullen wrote: > No RoCE, Just native IB with TCP over the top. Sorry, I'm confused - still not clear what is "Melanox III HCA 10G card". Could you run "ibstat" and post the results? What is the expected BW on your cards? Could you run "ib_write_bw" between two machines? Also, please see below. > No I haven't used 1.6 I was trying to stick with the standards on the mellanox disk. > Is there a known problem with 1.4.3 ? > >
 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
------------------------ > *From:* Yevgeny Kliteynik <kliteyn_at_[hidden]> > *To:* Randolph Pullen <randolph_pullen_at_[hidden]>; Open MPI Users <users_at_[hidden]> > *Sent:* Sunday, 2 September 2012 10:54 PM > *Subject:* Re: [OMPI users] Infiniband performance Problem and stalling > > Randolph, > > Some clarification on the setup: > > "Melanox III HCA 10G cards" - are those ConnectX 3 cards configured to Ethernet? > That is, when you're using openib BTL, you mean RoCE, right? > > Also, have you had a chance to try some newer OMPI release? > Any 1.6.x would do. > > > -- YK > > On 8/31/2012 10:53 AM, Randolph Pullen wrote: >  > (reposted with consolidatedinformation) >  > I have a test rig comprising 2 i7 systems 8GB RAM with Melanox III HCA 10G cards >  > running Centos 5.7 Kernel 2.6.18-274 >  > Open MPI 1.4.3 >  > MLNX_OFED_LINUX-1.5.3-1.0.0.2 (OFED-1.5.3-1.0.0.2): >  > On a Cisco 24 pt switch >  > Normal performance is: >  > $ mpirun --mca btl openib,self -n 2 -hostfile mpi.hosts PingPong >  > results in: >  > Max rate = 958.388867 MB/sec Min latency = 4.529953 usec >  > and: >  > $ mpirun --mca btl tcp,self -n 2 -hostfile mpi.hosts PingPong >  > Max rate = 653.547293 MB/sec Min latency = 19.550323 usec >  > NetPipeMPI results show a max of 7.4 Gb/s at 8388605 bytes which seems fine. >  > log_num_mtt =20 and log_mtts_per_seg params =2 >  > My application exchanges about a gig of data between the processes with 2 sender and 2 consumer processes on each node with 1 additional controller process on the starting node. >  > The program splits the data into 64K blocks and uses non blocking sends and receives with busy/sleep loops to monitor progress until completion. >  > Each process owns a single buffer for these 64K blocks. >  > My problem is I see better performance under IPoIB then I do on native IB (RDMA_CM). >  > My understanding is that IPoIB is limited to about 1G/s so I am at a loss to know why it is faster. >  > These 2 configurations are equivelant (about 8-10 seconds per cycle) >  > mpirun --mca btl_openib_flags 2 --mca mpi_leave_pinned 1 --mca btl tcp,self -H vh2,vh1 -np 9 --bycore prog >  > mpirun --mca btl_openib_flags 3 --mca mpi_leave_pinned 1 --mca btl tcp,self -H vh2,vh1 -np 9 --bycore prog When you say "--mca btl tcp,self", it means that openib btl is not enabled. Hence "--mca btl_openib_flags" is irrelevant. >  > And this one produces similar run times but seems to degrade with repeated cycles: >  > mpirun --mca btl_openib_eager_limit 64 --mca mpi_leave_pinned 1 --mca btl openib,self -H vh2,vh1 -np 9 --bycore prog You're running 9 ranks on two machines, but you're using IB for intra-node communication. Is it intentional? If not, you can add "sm" btl and have performance improved. -- YK >  > Other btl_openib_flags settings result in much lower performance. >  > Changing the first of the above configs to use openIB results in a 21 second run time at best. Sometimes it takes up to 5 minutes. >  > In all cases, OpenIB runs in twice the time it takes TCP,except if I push the small message max to 64K and force short messages. Then the openib times are the same as TCP and no faster. >  > With openib: >  > - Repeated cycles during a single run seem to slow down with each cycle >  > (usually by about 10 seconds). >  > - On occasions it seems to stall indefinitely, waiting on a single receive. >  > I'm still at a loss as to why. I can’t find any errors logged during the runs. >  > Any ideas appreciated. >  > Thanks in advance, >  > Randolph >  > >  > >  > _______________________________________________ >  > users mailing list >  > users_at_[hidden] <mailto:users_at_[hidden]> >  > http://www.open-mpi.org/mailman/listinfo.cgi/users > > >