[mpich-discuss] Controlling MPICH busy-wait behavior

[Mccall, Kurt E. (MSFC-EV41)]

Thanks Hui.  I will use MPI_Iprobe + MPI_Test.

Kurt

From: Zhou, Hui <zhouh at anl.gov>
Sent: Thursday, June 4, 2020 10:27 AM
To: discuss at mpich.org
Cc: Mccall, Kurt E. (MSFC-EV41) <kurt.e.mccall at nasa.gov>
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" <discuss at mpich.org<mailto:discuss at mpich.org>>
Reply-To: "discuss at mpich.org<mailto:discuss at mpich.org>" <discuss at mpich.org<mailto:discuss at mpich.org>>
Date: Wednesday, June 3, 2020 at 3:57 PM
To: "discuss at mpich.org<mailto:discuss at mpich.org>" <discuss at mpich.org<mailto:discuss at mpich.org>>
Cc: "Mccall, Kurt E. (MSFC-EV41)" <kurt.e.mccall at nasa.gov<mailto:kurt.e.mccall at nasa.gov>>
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/14562840#14562840<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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