[gmx-users] which item is gpu wait for cpu?

[Theodore Si]

That's a breakdown of the timings that CUDA cannot always measure.

What does that mean?

We run the same test case on the same machine. This "GPU timings" part didn't show up before, but now it appears.

在 9/25/2014 6:11 PM, Mark Abraham 写道:
> On Thu, Sep 25, 2014 at 11:57 AM, xiexiaobin at sjtu.edu.cn <
> xiexiaobin at sjtu.edu.cn> wrote:
>
>> Thanks.And I have another question want to ask.
>> I used the command "mdrun_mpi -v -deffnm test" to run the .tpr file and
>> find some new information in my log file:
>>
>>   GPU timings
>>
>> -----------------------------------------------------------------------------
>> Computing: Count Wall t (s) ms/step %
>>
>> -----------------------------------------------------------------------------
>> Pair list H2D 501 0.364 0.726 0.4
>> X / q H2D 20001 4.153 0.208 4.5
>> Nonbonded F kernel 18800 77.657 4.131 84.5
>> Nonbonded F+ene k. 700 4.060 5.800 4.4
>> Nonbonded F+prune k. 400 2.121 5.303 2.3
>> Nonbonded F+ene+prune k. 101 0.717 7.103 0.8
>> F D2H 20001 2.873 0.144 3.1
>>
>> -----------------------------------------------------------------------------
>> Total 91.946 4.597 100.0
>>
>> -----------------------------------------------------------------------------
>>
>> Force evaluation time GPU/CPU: 4.597 ms/5.245 ms = 0.876.
>>
>> But I used to use the some command and didn't appear such information.Does
>> anyone know why?
>>
> That's a breakdown of the timings that CUDA cannot always measure.
>
>
>> I also find that the time consuming of Nonbonded F kernel is 77.657s but
>> the time consuming of force is only 55.263s.Does the force item include
>> non-bonded force?
>
> No, it's non-PME work being done on the CPU (e.g. bonds, restraints,
> free-energy short-ranged)
>
> Mark
>
> If it was true,why the Nonbonded F kernel takes more time than the force ?
>>
>>
>> xiexiaobin at sjtu.edu.cn
>>
>> From: Szilárd Páll
>> Date: 2014-09-24 17:45
>> To: Discussion list for GROMACS users
>> CC: gromacs.org_gmx-users
>> Subject: Re: [gmx-users] which item is gpu wait for cpu?
>> On Wed, Sep 24, 2014 at 4:57 AM, xiexiaobin at sjtu.edu.cn
>> <xiexiaobin at sjtu.edu.cn> wrote:
>>> I think that the items (wait GPU nonlocal) and (wait GPU local) in log
>> file are the time consuming that cpu wait for gpu. And Does anyone know
>> that which item is the time consuming that gpu wait for cpu in log file?
>>
>> Due to a CUDA runtime limitation, that can not measured except for the
>> no domain-decomposition case (where it is expressed as overlap).
>>
>>>
>>> xiexiaobin at sjtu.edu.cn
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