[mpich-discuss] MPI_Comm_accept() pins cpu core 100%

[Balaji, Pavan]

This configuration does not support full MPI-3 and will be deprecated in the future.  You'll also lose some performance compared to the default configuration, but, well, you are oversubscribing cores, so I don't think that's as much of a concern in your case.

  -- Pavan

> On May 9, 2016, at 11:08 AM, Dmitriy Lyubimov <dlieu.7 at gmail.com> wrote:
> 
> ok, thank you. 
> 
> What implications does this have? does this reduce the solution capabilities/performance in any specific way?
> 
> for now, i ended up just bumping process priority to the max priority for the duration of accept call, which is still not great but i don't want to mess with the build capabilities or ask people to install a custom build.
> 
> On Mon, May 9, 2016 at 6:35 AM, Balaji, Pavan <balaji at anl.gov> wrote:
> 
> For now, the only workaround for this is to configure with --with-device=ch3:sock
> 
>   -- Pavan
> 
> > On May 6, 2016, at 5:49 PM, Dmitriy Lyubimov <dlieu.7 at gmail.com> wrote:
> >
> > Hi,
> >
> > I have a situation when a process my start up and execute MPI_Comm_accept(), while waiting for others to join, which may take some time.
> >
> > I have observed that all processes that wait in MPI_Comm_accept(), pin 1 cpu core exactly 100%.
> >
> > Which is unfortunate in my situation since if i launch enough processes, i pin the entire machine node very quickly -- and it does do other things that run into a crawl.
> >
> > Is this a known problem? is there a workaround for this?
> >
> > I tried on ubuntu 14-04 LTS which installs mpich 3.0.4 by default but i also tested 3.2 Nov/2015 and they both exhibit this very behavior.
> >
> > Thank you very much in advance.
> > -Dmitriy
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