I wrote an example of an interposition library that inserts usleep or nanosleep calls at microsecond granularity to blocking MPI operations. I have done minimal testing and not in the relevant circumstances (load-imbalance) so take it with a huge grain of salt. The intent is to be educational. https://github.com/jeffhammond/NiceWait Jeff On Thu, Jun 4, 2020 at 8:38 AM Jeff Hammond <[email protected]> wrote:

You might be able to implement this across the board using https://github.com/LLNL/wrap and interposing all calls to MPI_Wait transparently rather than changing the application code.

Jeff

On Thu, Jun 4, 2020 at 8:30 AM Mccall, Kurt E. (MSFC-EV41) via discuss < [email protected]> wrote:

...

Thanks Hui. I will use MPI_Iprobe + MPI_Test.

Kurt

*From:* Zhou, Hui <[email protected]> *Sent:* Thursday, June 4, 2020 10:27 AM *To:* [email protected] *Cc:* Mccall, Kurt E. (MSFC-EV41) <[email protected]> *Subject:* [EXTERNAL] Re: [mpich-discuss] Controlling MPICH busy-wait behavior

There is no such option for MPICH. If you configure with ch3:sock, which waits for the progress with blocking `poll`, I think it will not hog the CPU by default, for other configurations, it always busy waits.

Is using MPI_Iprobe + MPI_Test an option for you? If your process can afford latency, then you can control your own sleep cycles between MPI_Test. If MPICH will implement such non-busy-wait option, internally it will just do the same test-sleep cycles.

-- Hui Zhou

*From: *"Mccall, Kurt E. (MSFC-EV41) via discuss" <[email protected]> *Reply-To: *"[email protected]" <[email protected]> *Date: *Wednesday, June 3, 2020 at 3:57 PM *To: *"[email protected]" <[email protected]> *Cc: *"Mccall, Kurt E. (MSFC-EV41)" <[email protected]> *Subject: *[mpich-discuss] Controlling MPICH busy-wait behavior

Is there a means to tell MPICH to yield to other processes when performing a busy-wait for incoming messages? The page below distinguishes between “aggressive busy-wait” and “degraded busy-wait”, where the latter is what I’d like to try.

https://stackoverflow.com/questions/14560714/probe-seems-to-consume-the-cpu/... <https://urldefense.proofpoint.com/v2/url?u=https-3A__stackoverflow.com_questions_14560714_probe-2Dseems-2Dto-2Dconsume-2Dthe-2Dcpu_14562840-2314562840&d=DwMGaQ&c=ApwzowJNAKKw3xye91w7BE1XMRKi2LN9kiMk5Csz9Zk&r=6cP1IfXu3IZOHSDh_vBqciYiIh4uuVgs1MSi5K7l5fQ&m=stZqd9Fs3P0zmm4350zML37qvC5jT4e9jhayHaxrcbw&s=auPT9hTHN3AOIqD0_f-gKxki1W12bFbMF-6s6AGIL_w&e=>

Thanks,

Kurt

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-- Jeff Hammond [email protected] http://jeffhammond.github.io/

-- Jeff Hammond [email protected] http://jeffhammond.github.io/