I have applied the patch to both 1.10.0 and 1.10.1rc1. For 1.10.0 it did not help - I am not sure how much (if) you want pursue this.
For 1.10.1rc1 I was so far unable to reproduce any binding problems with jobs of up to 128 tasks. Some cosmetic suggestions. The warning it all started with says
MCW rank X is not bound (or bound to all available processors)1. One thing I already mentioned is that this warning is only displayed when using --report-bindings, and instead of printing the actual binding. I would suggest moving the warning somewhere else (maybe the bind_downwards/upwards functions?), and instead just show the binding in question. It might be trivial for homogeneous allocations, but is non-obvious with the type of SLURM jobs discussed. Also, seeing the warning only on the condition that --report-bindings was used, especially if the user specified binding policy manually, is IMHO wrong - OpenMPI should notify about failure somehow instead of quietly binding to all cores.
2. Another question altogether is if the warning should exist at all (instead of error, as proposed by Ralph). I still get that warning, even with 1.10.1rc1, in situations, in which I think it should not be displayed. In the simplest case the warning is printed when only 1 MPI task is running on a node. Obviously the statement is correct since the task is using all allocated CPUs, but its not useful. A more nontrivial case is when using '--bind-to socket', and when all MPI ranks are allocated on only one socket. Again, effectively all MPI ranks use all assigned cores and the warning is technically speaking correct, but misleading. Instead, as discussed in 1., it would be good to see the actual binding printed instead of the warning.
3. When I specify '--map-by hwthread --bind-to core', then I get multiple MPI processes bound to the same physical core without actually specifying --oversubscribe. Just a question whether it should be like this, but maybe yes.
On 10/05/2015 11:00 AM, Ralph Castain wrote:
I think this is okay, in general. I would only make one change: I would only search for an alternative site if the binding policy wasn’t set by the user. If the user specifies a mapping/binding pattern, then we should error out as we cannot meet it.
I think that would result in a non-transparent behavior in certain cases. By default mapping is done by socket, and OpenMPI could behave differently if '--map-by socket' is explicitly supplied on the command line - i.e., error out in jobs like discussed. Is this a good idea?
Introducing an error here is also a bit tricky. Consider allocating 5 mpi processes to 2 sockets. You would get an error in this type of distribution:
socket 0: 2 jobs socket 1: 3 jobs but not in this one socket 0: 3 jobs socket 1: 2 jobs just because you start counting from socket 0.
I did think of one alternative that might be worth considering. If we have a hetero topology, then we know that things are going to be a little unusual. In that case, we could just default to map-by core (or hwthread if —use-hwthread-cpus was given) and then things would be fine even in non-symmetric topologies. Likewise, if we have a homogeneous topology, we could just quickly check for symmetry on our base topology (the one we will use for mapping) and default to map-by core if non-symmetric.
Having different default options for different cases becomes difficult to manage and understand. If I could vote, I would rather go for an informative error. Or to switch to '--map-by core' as default for all cases ;) (probably not gonna happen..)
Removing support of '--map-by socket' altogether for this type of jobs is likely OK - don't know. I personally like the new way it works - if there are resources, use them. But if you end up removing this possibility it would probably be good to put it into SLURM related doc and produce some meaningful error.
Marcin
I suggest it only because we otherwise wind up with some oddball hybrid mapping scheme. In the case we have here, procs would be mapped by socket except where we have an extra core, where they would look like they were mapped by core. Impossible to predict how the app will react to it.
The alternative be a more predictable pattern - would it make more sense? RalphOn Oct 5, 2015, at 1:13 AM, Gilles Gouaillardet <gil...@rist.or.jp <mailto:gil...@rist.or.jp>> wrote:Ralph and Marcin,here is a proof of concept for a fix (assert should be replaced with proper error handling)for v1.10 branch. if you have any chance to test it, please let me know the results Cheers, Gilles On 10/5/2015 1:08 PM, Gilles Gouaillardet wrote:OK, i'll see what i can do :-) On 10/5/2015 12:39 PM, Ralph Castain wrote:I would consider that a bug, myself - if there is some resource available, we should use itOn Oct 4, 2015, at 5:42 PM, Gilles Gouaillardet <gil...@rist.or.jp <mailto:gil...@rist.or.jp>> wrote:Marcin, i ran a simple test with v1.10.1rc1 under a cpuset with - one core (two threads 0,16) on socket 0 - two cores (two threads each 8,9,24,25) on socket 1 $ mpirun -np 3 -bind-to core ./hello_c -------------------------------------------------------------------------- A request was made to bind to that would result in binding more processes than cpus on a resource: Bind to: CORE Node: rapid #processes: 2 #cpus: 1 You can override this protection by adding the "overload-allowed" option to your binding directive. -------------------------------------------------------------------------- as you already pointed, default mapping is by socket. so on one hand, we can consider this behavior is a feature :we try to bind two processes to socket 0, so the --oversubscribe option is required(and it does what it should :$ mpirun -np 3 -bind-to core --oversubscribe -report-bindings ./hello_c [rapid:16278] MCW rank 0 bound to socket 0[core 0[hwt 0-1]]: [BB/../../../../../../..][../../../../../../../..] [rapid:16278] MCW rank 1 bound to socket 1[core 8[hwt 0-1]]: [../../../../../../../..][BB/../../../../../../..] [rapid:16278] MCW rank 2 bound to socket 0[core 0[hwt 0-1]]: [BB/../../../../../../..][../../../../../../../..] Hello, world, I am 1 of 3, (Open MPI v1.10.1rc1, package: Open MPI gilles@rapid Distribution, ident: 1.10.1rc1, repo rev: v1.10.0-84-g15ae63f, Oct 03, 2015, 128) Hello, world, I am 2 of 3, (Open MPI v1.10.1rc1, package: Open MPI gilles@rapid Distribution, ident: 1.10.1rc1, repo rev: v1.10.0-84-g15ae63f, Oct 03, 2015, 128) Hello, world, I am 0 of 3, (Open MPI v1.10.1rc1, package: Open MPI gilles@rapid Distribution, ident: 1.10.1rc1, repo rev: v1.10.0-84-g15ae63f, Oct 03, 2015, 128)and on the other hand, we could consider ompi should be a bit smarter, and uses socket 1 for task 2 since socket 0 is fully allocated and there is room on socket 1.Ralph, any thoughts ? bug or feature ? Marcin, you mentionned you had one failure with 1.10.1rc1 and -bind-to core could you please send the full details (script, allocation and output) in your slurm script, you can dosrun -N $SLURM_NNODES -n $SLURM_NNODES --cpu_bind=none -l grep Cpus_allowed_list /proc/self/statusbefore invoking mpirun Cheers, Gilles On 10/4/2015 11:55 PM, marcin.krotkiewski wrote:Hi, all, I played a bit more and it seems that the problem results from trg_obj = opal_hwloc_base_find_min_bound_target_under_obj()called in rmaps_base_binding.c / bind_downwards being wrong. I do not know the reason, but I think I know when the problem happens (at least on 1.10.1rc1). It seems that by default openmpi maps by socket. The error happens when for a given compute node there is a different number of cores used on each socket. Consider previously studied case (the debug outputs I sent in last post). c1-8, which was source of error, has 5 mpi processes assigned, and the cpuset is the following:0, 5, 9, 13, 14, 16, 21, 25, 29, 30Cores 0,5 are on socket 0, cores 9, 13, 14 are on socket 1. Binding progresses correctly up to and including core 13 (see end of file out.1.10.1rc2, before the error). That is 2 cores on socket 0, and 2 cores on socket 1. Error is thrown when core 14 should be bound - extra core on socket 1 with no corresponding core on socket 0. At that point the returned trg_obj points to the first core on the node (os_index 0, socket 0).I have submitted a few other jobs and I always had an error in such situation. Moreover, if I now use --map-by core instead of socket, the error is gone, and I get my expected binding:rank 0 @ compute-1-2.local 1, 17, rank 1 @ compute-1-2.local 2, 18, rank 2 @ compute-1-2.local 3, 19, rank 3 @ compute-1-2.local 4, 20, rank 4 @ compute-1-4.local 1, 17, rank 5 @ compute-1-4.local 15, 31, rank 6 @ compute-1-8.local 0, 16, rank 7 @ compute-1-8.local 5, 21, rank 8 @ compute-1-8.local 9, 25, rank 9 @ compute-1-8.local 13, 29, rank 10 @ compute-1-8.local 14, 30, rank 11 @ compute-1-13.local 3, 19, rank 12 @ compute-1-13.local 4, 20, rank 13 @ compute-1-13.local 5, 21, rank 14 @ compute-1-13.local 6, 22, rank 15 @ compute-1-13.local 7, 23, rank 16 @ compute-1-16.local 12, 28, rank 17 @ compute-1-16.local 13, 29, rank 18 @ compute-1-16.local 14, 30, rank 19 @ compute-1-16.local 15, 31, rank 20 @ compute-1-23.local 2, 18, rank 29 @ compute-1-26.local 11, 27, rank 21 @ compute-1-23.local 3, 19, rank 30 @ compute-1-26.local 13, 29, rank 22 @ compute-1-23.local 4, 20, rank 31 @ compute-1-26.local 15, 31, rank 23 @ compute-1-23.local 8, 24, rank 27 @ compute-1-26.local 1, 17, rank 24 @ compute-1-23.local 13, 29, rank 28 @ compute-1-26.local 6, 22, rank 25 @ compute-1-23.local 14, 30, rank 26 @ compute-1-23.local 15, 31,Using --map-by core seems to fix the issue on 1.8.8, 1.10.0 and 1.10.1rc1. However, there is still a difference in behavior between 1.10.1rc1 and earlier versions. In the SLURM job described in last post, 1.10.1rc1 fails to bind only in 1 case, while the earlier versions fail in 21 out of 32 cases. You mentioned there was a bug in hwloc. Not sure if it can explain the difference in behavior.Hope this helps to nail this down. Marcin On 10/04/2015 09:55 AM, Gilles Gouaillardet wrote:Ralph, I suspect ompi tries to bind to threads outside the cpuset.this could be pretty similar to a previous issue when ompi tried to bind to cores outside the cpuset. /* when a core has more than one thread, would ompi assume all the threads are available if the core is available ? */I will investigate this from tomorrow Cheers, Gilles On Sunday, October 4, 2015, Ralph Castain <r...@open-mpi.org> wrote: Thanks - please go ahead and release that allocation as I’m not going to get to this immediately. I’ve got several hot irons in the fire right now, and I’m not sure when I’ll get a chance to track this down. Gilles or anyone else who might have time - feel free to take a gander and see if something pops out at you. RalphOn Oct 3, 2015, at 11:05 AM, marcin.krotkiewski <marcin.krotkiew...@gmail.com> wrote: Done. I have compiled 1.10.0 and 1.10.rc1 with --enable-debug and executed mpirun --mca rmaps_base_verbose 10 --hetero-nodes --report-bindings --bind-to core -np 32 ./affinity In case of 1.10.rc1 I have also added :overload-allowed - output in a separate file. This option did not make much difference for 1.10.0, so I did not attach it here. First thing I noted for 1.10.0 are lines like [login-0-1.local:03399] [[37945,0],0] GOT 1 CPUS [login-0-1.local:03399] [[37945,0],0] PROC [[37945,1],27] BITMAP [login-0-1.local:03399] [[37945,0],0] PROC [[37945,1],27] ON c1-26 IS NOT BOUND with an empty BITMAP. The SLURM environment is set | grep SLURM SLURM_JOBID=12714491 SLURM_JOB_CPUS_PER_NODE='4,2,5(x2),4,7,5' SLURM_JOB_ID=12714491 SLURM_JOB_NODELIST='c1-[2,4,8,13,16,23,26]' SLURM_JOB_NUM_NODES=7 SLURM_JOB_PARTITION=normal SLURM_MEM_PER_CPU=2048 SLURM_NNODES=7 SLURM_NODELIST='c1-[2,4,8,13,16,23,26]' SLURM_NODE_ALIASES='(null)' SLURM_NPROCS=32 SLURM_NTASKS=32 SLURM_SUBMIT_DIR=/cluster/home/marcink SLURM_SUBMIT_HOST=login-0-1.local SLURM_TASKS_PER_NODE='4,2,5(x2),4,7,5' I have submitted an interactive job on screen for 120 hours now to work with one example, and not change it for every post :) If you need anything else, let me know. I could introduce some patch/printfs and recompile, if you need it. Marcin On 10/03/2015 07:17 PM, Ralph Castain wrote:Rats - just realized I have no way to test this as none of the machines I can access are setup for cgroup-based multi-tenant. Is this a debug version of OMPI? If not, can you rebuild OMPI with —enable-debug? Then please run it with —mca rmaps_base_verbose 10 and pass along the output. Thanks RalphOn Oct 3, 2015, at 10:09 AM, Ralph Castain <r...@open-mpi.org> wrote: What version of slurm is this? I might try to debug it here. I’m not sure where the problem lies just yet.On Oct 3, 2015, at 8:59 AM, marcin.krotkiewski <marcin.krotkiew...@gmail.com> wrote: Here is the output of lstopo. In short, (0,16) are core 0, (1,17) - core 1 etc. Machine (64GB) NUMANode L#0 (P#0 32GB) Socket L#0 + L3 L#0 (20MB) L2 L#0 (256KB) + L1d L#0 (32KB) + L1i L#0 (32KB) + Core L#0 PU L#0 (P#0) PU L#1 (P#16) L2 L#1 (256KB) + L1d L#1 (32KB) + L1i L#1 (32KB) + Core L#1 PU L#2 (P#1) PU L#3 (P#17) L2 L#2 (256KB) + L1d L#2 (32KB) + L1i L#2 (32KB) + Core L#2 PU L#4 (P#2) PU L#5 (P#18) L2 L#3 (256KB) + L1d L#3 (32KB) + L1i L#3 (32KB) + Core L#3 PU L#6 (P#3) PU L#7 (P#19) L2 L#4 (256KB) + L1d L#4 (32KB) + L1i L#4 (32KB) + Core L#4 PU L#8 (P#4) PU L#9 (P#20) L2 L#5 (256KB) + L1d L#5 (32KB) + L1i L#5 (32KB) + Core L#5 PU L#10 (P#5) PU L#11 (P#21) L2 L#6 (256KB) + L1d L#6 (32KB) + L1i L#6 (32KB) + Core L#6 PU L#12 (P#6) PU L#13 (P#22) L2 L#7 (256KB) + L1d L#7 (32KB) + L1i L#7 (32KB) + Core L#7 PU L#14 (P#7) PU L#15 (P#23) HostBridge L#0 PCIBridge PCI 8086:1521 Net L#0 "eth0" PCI 8086:1521 Net L#1 "eth1" PCIBridge PCI 15b3:1003 Net L#2 "ib0" OpenFabrics L#3 "mlx4_0" PCIBridge PCI 102b:0532 PCI 8086:1d02 Block L#4 "sda" NUMANode L#1 (P#1 32GB) + Socket L#1 + L3 L#1 (20MB) L2 L#8 (256KB) + L1d L#8 (32KB) + L1i L#8 (32KB) + Core L#8 PU L#16 (P#8) PU L#17 (P#24) L2 L#9 (256KB) + L1d L#9 (32KB) + L1i L#9 (32KB) + Core L#9 PU L#18 (P#9) PU L#19 (P#25) L2 L#10 (256KB) + L1d L#10 (32KB) + L1i L#10 (32KB) + Core L#10 PU L#20 (P#10) PU L#21 (P#26) L2 L#11 (256KB) + L1d L#11 (32KB) + L1i L#11 (32KB) + Core L#11 PU L#22 (P#11) PU L#23 (P#27) L2 L#12 (256KB) + L1d L#12 (32KB) + L1i L#12 (32KB) + Core L#12 PU L#24 (P#12) PU L#25 (P#28) L2 L#13 (256KB) + L1d L#13 (32KB) + L1i L#13 (32KB) + Core L#13 PU L#26 (P#13) PU L#27 (P#29) L2 L#14 (256KB) + L1d L#14 (32KB) + L1i L#14 (32KB) + Core L#14 PU L#28 (P#14) PU L#29 (P#30) L2 L#15 (256KB) + L1d L#15 (32KB) + L1i L#15 (32KB) + Core L#15 PU L#30 (P#15) PU L#31 (P#31) On 10/03/2015 05:46 PM, Ralph Castain wrote:Maybe I’m just misreading your HT map - that slurm nodelist syntax is a new one to me, but they tend to change things around. Could you run lstopo on one of those compute nodes and send the output? I’m just suspicious because I’m not seeing a clear pairing of HT numbers in your output, but HT numbering is BIOS-specific and I may just not be understanding your particular pattern. Our error message is clearly indicating that we are seeing individual HTs (and not complete cores) assigned, and I don’t know the source of that confusion.On Oct 3, 2015, at 8:28 AM, marcin.krotkiewski <marcin.krotkiew...@gmail.com> wrote: On 10/03/2015 04:38 PM, Ralph Castain wrote:If mpirun isn’t trying to do any binding, then you will of course get the right mapping as we’ll just inherit whatever we received.Yes. I meant that whatever you received (what SLURM gives) is a correct cpu map and assigns _whole_ CPUs, not a single HT to MPI processes. In the case mentioned earlier openmpi should start 6 tasks on c1-30. If HT would be treated as separate and independent cores, sched_getaffinity of an MPI process started on c1-30 would return a map with 6 entries only. In my case it returns a map with 12 entries - 2 for each core. So one process is in fact allocated both HTs, not only one. Is what I'm saying correct?Looking at your output, it’s pretty clear that you are getting independent HTs assigned and not full cores.How do you mean? Is the above understanding wrong? I would expect that on c1-30 with --bind-to core openmpi should bind to logical cores 0 and 16 (rank 0), 1 and 17 (rank 2) and so on. All those logical cores are available in sched_getaffinity map, and there is twice as many logical cores as there are MPI processes started on the node.My guess is that something in slurm has changed such that it detects that HT has been enabled, and then begins treating the HTs as completely independent cpus. Try changing “-bind-to core” to “-bind-to hwthread -use-hwthread-cpus” and see if that worksI have and the binding is wrong. For example, I got this output rank 0 @ compute-1-30.local 0, rank 1 @ compute-1-30.local 16, Which means that two ranks have been bound to the same physical core (logical cores 0 and 16 are two HTs of the same core). If I use --bind-to core, I get the following correct binding rank 0 @ compute-1-30.local 0, 16, The problem is many other ranks get bad binding with 'rank XXX is not bound (or bound to all available processors)' warning. But I think I was not entirely correct saying that 1.10.1rc1 did not fix things. It still might have improved something, but not everything. Consider this job: SLURM_JOB_CPUS_PER_NODE='5,4,6,5(x2),7,5,9,5,7,6' SLURM_JOB_NODELIST='c8-[31,34],c9-[30-32,35-36],c10-[31-34]' If I run 32 tasks as follows (with 1.10.1rc1) mpirun --hetero-nodes --report-bindings --bind-to core -np 32 ./affinity I get the following error: -------------------------------------------------------------------------- A request was made to bind to that would result in binding more processes than cpus on a resource: Bind to: CORE Node: c9-31 #processes: 2 #cpus: 1 You can override this protection by adding the "overload-allowed" option to your binding directive. -------------------------------------------------------------------------- If I now use --bind-to core:overload-allowed, then openmpi starts and _most_ of the threads are bound correctly (i.e., map contains two logical cores in ALL cases), except this case that required the overload flag: rank 15 @ compute-9-31.local 1, 17, rank 16 @ compute-9-31.local 11, 27, rank 17 @ compute-9-31.local 2, 18, rank 18 @ compute-9-31.local 12, 28, rank 19 @ compute-9-31.local 1, 17, Note pair 1,17 is used twice. The original SLURM delivered map (no binding) on this node is rank 15 @ compute-9-31.local 1, 2, 11, 12, 13, 17, 18, 27, 28, 29, rank 16 @ compute-9-31.local 1, 2, 11, 12, 13, 17, 18, 27, 28, 29, rank 17 @ compute-9-31.local 1, 2, 11, 12, 13, 17, 18, 27, 28, 29, rank 18 @ compute-9-31.local 1, 2, 11, 12, 13, 17, 18, 27, 28, 29, rank 19 @ compute-9-31.local 1, 2, 11, 12, 13, 17, 18, 27, 28, 29, Why does openmpi use cores (1,17) twice instead of using core (13,29)? Clearly, the original SLURM-delivered map has 5 CPUs included, enough for 5 MPI processes. Cheers, MarcinOn Oct 3, 2015, at 7:12 AM, marcin.krotkiewski <marcin.krotkiew...@gmail.com> wrote: On 10/03/2015 01:06 PM, Ralph Castain wrote:Thanks Marcin. Looking at this, I’m guessing that Slurm may be treating HTs as “cores” - i.e., as independent cpus. Any chance that is true?Not to the best of my knowledge, and at least not intentionally. SLURM starts as many processes as there are physical cores, not threads. To verify this, consider this test case:_______________________________________________ users mailing list us...@open-mpi.org Subscription:http://www.open-mpi.org/mailman/listinfo.cgi/users Link to this post:http://www.open-mpi.org/community/lists/users/2015/10/27790.php_______________________________________________ users mailing list us...@open-mpi.org Subscription:http://www.open-mpi.org/mailman/listinfo.cgi/users Link to this post:http://www.open-mpi.org/community/lists/users/2015/10/27791.php_______________________________________________ users mailing list us...@open-mpi.org <mailto:us...@open-mpi.org> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/usersLink to this post: http://www.open-mpi.org/community/lists/users/2015/10/27792.php_______________________________________________ users mailing list us...@open-mpi.org Subscription:http://www.open-mpi.org/mailman/listinfo.cgi/users Link to this post:http://www.open-mpi.org/community/lists/users/2015/10/27793.php_______________________________________________ users mailing list us...@open-mpi.org Subscription:http://www.open-mpi.org/mailman/listinfo.cgi/users Link to this post:http://www.open-mpi.org/community/lists/users/2015/10/27794.php<unbalanced.patch>_______________________________________________ users mailing list us...@open-mpi.org <mailto:us...@open-mpi.org> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/usersLink to this post: http://www.open-mpi.org/community/lists/users/2015/10/27795.php_______________________________________________ users mailing list us...@open-mpi.org Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users Link to this post: http://www.open-mpi.org/community/lists/users/2015/10/27796.php
