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* [dpdk-dev] Service lcores and Application lcores
@ 2017-06-29 14:36 Van Haaren, Harry
  2017-06-29 15:16 ` Thomas Monjalon
  2017-06-29 15:57 ` Bruce Richardson
  0 siblings, 2 replies; 19+ messages in thread
From: Van Haaren, Harry @ 2017-06-29 14:36 UTC (permalink / raw)
  To: dev; +Cc: 'Jerin Jacob', thomas, Wiles, Keith, Richardson, Bruce

Hi All,


The recently posted service cores patchset[1], introduces service lcores to run services for DPDK applications. Services are just an ordinary function for eg: eventdev scheduling, NIC RX, statistics and monitoring, etc. A service is just a callback function, which a core invokes. An atomic ensures that services that are
non-multi-thread-safe are never concurrently invoked.

The topic of discussion in this thread is how we can ensure that application lcores do not interfere with service cores. I have a solution described below, opinions welcome.


Regards, -Harry


PS: This discussion extends that in the ML thread here[2], participants of that thread added to CC.

[1] Service Cores v2 patchset http://dpdk.org/dev/patchwork/bundle/hvanhaar/service_cores_v2/
[2] http://dpdk.org/ml/archives/dev/2017-June/069290.html


________________________



A proposal for Eventdev, to ensure Service lcores and Application lcores play nice;

1) Application lcores must not directly call rte_eventdev_schedule()
2A) Service cores are the proper method to run services
2B) If an application insists on running a service "manually" on an app lcore, we provide a function for that:
     rte_service_run_from_app_lcore(struct service *srv);

The above function would allow a pesky app to run services on its own (non-service core) lcores, but
does so through the service-core framework, allowing the service-library atomic to keep access serialized as required for non-multi-thread-safe services.

The above solution maintains the option of running the eventdev PMD as now (single-core dedicated to a single service), while providing correct serialization by using the rte_service_run_from_app_lcore() function. Given the atomic is only used when required (multiple cores mapped to the service) there should be no performance delta.

Given that the application should not invoke rte_eventdev_schedule(), we could even consider removing it from the Eventdev API. A PMD that requires cycles registers a service, and an application can use a service core or the run_from_app_lcore() function if it wishes to invoke that service on an application owned lcore.


Opinions?

^ permalink raw reply	[flat|nested] 19+ messages in thread

end of thread, other threads:[~2017-06-30 13:51 UTC | newest]

Thread overview: 19+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-06-29 14:36 [dpdk-dev] Service lcores and Application lcores Van Haaren, Harry
2017-06-29 15:16 ` Thomas Monjalon
2017-06-29 16:35   ` Van Haaren, Harry
2017-06-29 20:18     ` Thomas Monjalon
2017-06-30  8:52       ` Van Haaren, Harry
2017-06-30  9:29         ` Thomas Monjalon
2017-06-30 10:18           ` Van Haaren, Harry
2017-06-30 10:38             ` Thomas Monjalon
2017-06-30 11:14               ` Van Haaren, Harry
2017-06-30 13:04                 ` Jerin Jacob
2017-06-30 13:16                   ` Van Haaren, Harry
2017-06-29 15:57 ` Bruce Richardson
2017-06-30  4:45   ` Jerin Jacob
2017-06-30 10:00     ` Van Haaren, Harry
2017-06-30 12:51       ` Jerin Jacob
2017-06-30 13:08         ` Van Haaren, Harry
2017-06-30 13:20           ` Jerin Jacob
2017-06-30 13:24             ` Van Haaren, Harry
2017-06-30 13:51               ` Thomas Monjalon

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