Re: [dpdk-dev] Query regarding multiple processes in DPDK

[Prashant Upadhyaya <prashant.upadhyaya@aricent.com>]

Hi Bruce,

One more question --

Suppose the first instance comes up as primary and creates the mbuf pool and rings etc. [ok]
Now, the second instance comes up as secondary and does the corresponding lookup functions [ok]
Now the primary exits -- at this point can the secondary still run with all the memory to which it had done the lookup intact, or does the fact that primary died will lead to all the memory also taken away with it so that the secondary can no longer function now ?

Regards
-Prashant


-----Original Message-----
From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Prashant Upadhyaya
Sent: Friday, November 22, 2013 7:16 PM
To: Richardson, Bruce; dev@dpdk.org
Subject: Re: [dpdk-dev] Query regarding multiple processes in DPDK

Thanks Bruce, I think your suggested example of multi_process answers my questions.

Regards
-Prashant


-----Original Message-----
From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Prashant Upadhyaya
Sent: Friday, November 22, 2013 7:10 PM
To: Richardson, Bruce; dev@dpdk.org
Subject: Re: [dpdk-dev] Query regarding multiple processes in DPDK

Hi Bruce,

Thanks.

Regarding your comment --
[BR] It will depend upon the application, but in most cases you probably want to have slightly different code paths for primary and secondary instances. For example, if a process is running as primary instance, it will probably call rte_mempool_create or rte_ring_create. A secondary instance which wants to use these should instead call rte_mempool_lookup and rte_ring_lookup instead.
For an example of how to write the one binary to be used as both primary and secondary process, I suggest looking at the symmetric_mp example application in the examples/multi_process/ directory.

I was really hoping that the --proc-type=auto, would make the DPDK libraries internally resolving all this stuff, is that not the case ? I have not started reading the code for all this yet.
I must launch the same executable twice in my usecase. Even if the executable code has to make different calls when it comes up as secondary, is there a way for the usercode to know that it has really come up as secondary when the --proc-type=auto is used ?

Regards
-Prashant

-----Original Message-----
From: Richardson, Bruce [mailto:bruce.richardson@intel.com]
Sent: Friday, November 22, 2013 7:02 PM
To: Prashant Upadhyaya; dev@dpdk.org
Subject: RE: Query regarding multiple processes in DPDK

Hi Prashant

> ===
> The EAL also supports an auto-detection mode (set by EAL
> --proc-type=auto flag), whereby an Intel(r) DPDK process is started as
> a secondary instance if a primary instance is already running.
> ===
>
> So does this mean that if I have a DPDK exe foo.out, then when I run
> the first instance of foo.out with -proc-type = auto, then foo.out
> will run as a primary process and when I spawn the second instance of
> foo.out (with first already running) again with -proc-type=auto, then
> this second instance automatically becomes secondary ?
[BR] Yes, that is the idea.

>
> Also is there any user code initialization change required or exactly
> the same code will work for both the processes ?
[BR] It will depend upon the application, but in most cases you probably want to have slightly different code paths for primary and secondary instances. For example, if a process is running as primary instance, it will probably call rte_mempool_create or rte_ring_create. A secondary instance which wants to use these should instead call rte_mempool_lookup and rte_ring_lookup instead.
For an example of how to write the one binary to be used as both primary and secondary process, I suggest looking at the symmetric_mp example application in the examples/multi_process/ directory.

Regards,
/Bruce





===============================================================================
Please refer to http://www.aricent.com/legal/email_disclaimer.html
for important disclosures regarding this electronic communication.
===============================================================================




===============================================================================
Please refer to http://www.aricent.com/legal/email_disclaimer.html
for important disclosures regarding this electronic communication.
===============================================================================




===============================================================================
Please refer to http://www.aricent.com/legal/email_disclaimer.html
for important disclosures regarding this electronic communication.
===============================================================================