Re: DPDK and energy efficiency

[Etienne-Victor Depasquale <edepa () ieee org>]

> No, it is not PMD that runs the processor in a polling loop.
> It is the application itself, thay may or may not busy loop,
> depending on application programmers choice.

> From one of my earlier references [2]:

"we found that a poll mode driver (PMD)
thread accounted for approximately 99.7 percent
CPU occupancy (a full core utilization)."

And further on:

"we found that the thread kept spinning on the following code block:




*for ( ; ; ) {for ( i = 0; i < poll_cnt; i ++) {dp_netdev_process_rxq_port
(pmd, list[i].port, poll_list[i].rx) ;}}*
This indicates that the thread was continuously
monitoring and executing the receiving data path."


[2] S. Fu, J. Liu, and W. Zhu, “Multimedia Content Delivery with Network
Function Virtualization: The Energy Perspective,”
 IEEE MultiMedia, vol. 24, no. 3, pp. 38–47, 2017, ISSN: 1941-0166.
DOI: 10.1109/MMUL.2017.3051514.

On Tue, Feb 23, 2021 at 12:59 PM Pawel Malachowski <
pawmal-nanog () freebsd lublin pl> wrote:

> Dnia Mon, Feb 22, 2021 at 12:45:52PM +0100, Etienne-Victor Depasquale
> napisał(a):
>
> > Every research paper I've read indicates that, regardless of whether it
> has
> > packets to process or not, DPDK PMDs (poll-mode drivers) prevent the CPU
> > from falling into an LPI (low-power idle).
> >
> > When it has no packets to process, the PMD runs the processor in a
> polling
> > loop that keeps utilization of the running core at 100%.
>
> No, it is not PMD that runs the processor in a polling loop.
> It is the application itself, thay may or may not busy loop,
> depending on application programmers choice.
>
>
> --
> Pawel Malachowski
> @pawmal80


-- 
Ing. Etienne-Victor Depasquale
Assistant Lecturer
Department of Communications & Computer Engineering
Faculty of Information & Communication Technology
University of Malta
Web. https://www.um.edu.mt/profile/etiennedepasquale