Re: [hwloc-users] memory binding on Knights Landing

2016-09-08 Thread Jeff Hammond
On Thu, Sep 8, 2016 at 8:59 AM, Dave Love  wrote:

> Brice Goglin  writes:
>
> > Hello
> > It's not a feature. This should work fine.
> > Random guess: do you have NUMA headers on your build machine ? (package
> > libnuma-dev or numactl-devel)
> > (hwloc-info --support also report whether membinding is supported or not)
> > Brice
>
> Oops, you're right!  Thanks.  I thought what I'm using elsewhere was
> built from the same srpm, but the rpm on the KNL box doesn't actually
> require libnuma.  After a rebuild, it's OK and I'm suitably embarrassed.
>
> By the way, is it expected that binding will be slow on it?  hwloc-bind
> is ~10 times slower (~1s) than on two-socket sandybridge, and ~3 times
> slower than on a 128-core, 16-socket system.
>
> Is this a bottleneck in any application?  Are there codes bindings memory
frequently?

Because most things inside the kernel are limited by single-threaded
performance, it is reasonable for them to be slower than on a Xeon
processor, but I've not seen slowdowns that high.

Jeff

-- 
Jeff Hammond
jeff.scie...@gmail.com
http://jeffhammond.github.io/
___
hwloc-users mailing list
hwloc-users@lists.open-mpi.org
https://rfd.newmexicoconsortium.org/mailman/listinfo/hwloc-users

Re: [hwloc-users] memory binding on Knights Landing

2016-09-08 Thread Brice Goglin
Hello
It's not a feature. This should work fine.
Random guess: do you have NUMA headers on your build machine ? (package
libnuma-dev or numactl-devel)
(hwloc-info --support also report whether membinding is supported or not)
Brice



Le 08/09/2016 16:34, Dave Love a écrit :
> I'm somewhat confused by binding on Knights Landing -- which is probably
> a feature.
>
> I'm looking at a KNL box configured as "Cluster Mode: SNC4 Memory Mode:
> Cache" with hwloc 1.11.4; I've read the KNL hwloc FAQ entries.  I ran
> openmpi and it reported failure to bind memory (but binding to cores was
> OK).  So I tried hwloc-bind --membind and that seems to fail with no
> matter what I do, reporting
>
>   hwloc_set_membind 0x0002 (policy 2 flags 0) failed (errno 38 Function 
> not implemented)
>
> Is that expected, and is there a recommendation on how to do binding in
> that configuration with things that use hwloc?  I'm particularly
> interested in OMPI, but I guess this is a better place to ask.  Thanks.
> ___
> hwloc-users mailing list
> hwloc-users@lists.open-mpi.org
> https://rfd.newmexicoconsortium.org/mailman/listinfo/hwloc-users

___
hwloc-users mailing list
hwloc-users@lists.open-mpi.org
https://rfd.newmexicoconsortium.org/mailman/listinfo/hwloc-users