Re: [Starpu-devel] Performance issue of StarPU on Intel self-hosted KNL

[Mawussi Zounon <mawussi.zounon@manchester.ac.uk>]

Hi Oliver,

It can worth including the StarPU initialization in at least one routine, for 
the sake of comparison, 
just to evaluate the gain of the Samuel's improvement.

Best regards,
--Mawussi 
________________________________________
From: Olivier Aumage [olivier.aumage@inria.fr]
Sent: Monday, September 25, 2017  5:13 PM
To: Mawussi Zounon
Cc: Samuel Thibault; Negin Bagherpour; starpu-devel@lists.gforge.inria.fr; 
Jakub Sistek
Subject: Re: [Starpu-devel] Performance issue of StarPU on Intel self-hosted 
KNL

> Le 25 sept. 2017 à 12:10, Mawussi Zounon <mawussi.zounon@manchester.ac.uk> 
> a écrit :
>
> Thanks Samuel,
>
> I will perform a quick benchmark then be back to you.
>
Hi Mawussi,

Even with a single topology load from hwloc now, it is still not advised to 
perform a starpu_init()/starpu_shutdown() on every PLASMA call. :-)

Best regards,
--
Olivier

> Best regards,
> --Mawussi
> ________________________________________
> From: Samuel Thibault [samuel.thibault@inria.fr]
> Sent: Monday, September 25, 2017 1:16 PM
> To: Olivier Aumage; Mawussi Zounon; Negin Bagherpour; 
> starpu-devel@lists.gforge.inria.fr; Jakub Sistek
> Subject: Re: [Starpu-devel] Performance issue of StarPU on Intel 
> self-hosted KNL
>
> Samuel Thibault, on ven. 22 sept. 2017 11:48:12 +0200, wrote:
>> Olivier Aumage, on ven. 22 sept. 2017 09:12:27 +0200, wrote:
>>> The main reason for the initialization cost on KNL is the large number of 
>>> cores and the fact that those cores are individually much less powerful 
>>> and advanced than Broadwell's cores. Initializing libhwloc on the KNL 
>>> takes about 0.5 to 1 second.
>>
>> And we do it twice, once for the whole architecture, and a second
>> time in _starpu_build_tree to get only the structure of the
>> architecture. Perhaps that second call could be avoided, it's probably
>> less expensive to make build_tree cope with structure-useless hwloc
>> object, than asking hwloc discovery a second time.
>
> I have fixed this.
>
> Samuel