[dpdk-dev] [EXT] Re: [PATCH 3/3] l3fwd-power: add interrupt-only mode

Harman Kalra hkalra at marvell.com
Tue Jun 2 12:23:07 CEST 2020


On Mon, Jun 01, 2020 at 01:50:26PM +0100, Burakov, Anatoly wrote:
> On 30-May-20 11:02 AM, Harman Kalra wrote:
> > On Fri, May 29, 2020 at 03:19:45PM +0100, Burakov, Anatoly wrote:
> > > External Email
> > > 
> > > ----------------------------------------------------------------------
> > > On 29-May-20 2:19 PM, Harman Kalra wrote:
> > > 
> > > > >    	if (ret < 0)
> > > > >    		rte_exit(EXIT_FAILURE, "Invalid L3FWD parameters\n");
> > > > > -	if (app_mode != APP_MODE_TELEMETRY && init_power_library())
> > > > > +	if (app_mode == APP_MODE_DEFAULT)
> > > > > +		app_mode = APP_MODE_LEGACY;
> > > > > +
> > > > > +	/* only legacy and empty poll mode rely on power library */
> > > > > +	if ((app_mode == APP_MODE_LEGACY || app_mode == APP_MODE_EMPTY_POLL) &&
> > > > > +			init_power_library())
> > > > >    		rte_exit(EXIT_FAILURE, "init_power_library failed\n");
> > > > Hi,
> > > > 
> > > > Rather than just exiting from here can we have a else condition to
> > > > automatically enter into the "interrupt only" mode.
> > > > Please correct me if I am missing something.
> > > 
> > > Hi,
> > > 
> > > Thanks for your review. I don't think silently proceeding is a good idea. If
> > > the user wants interrupt-only mode, they should request it. Silently falling
> > > back to interrupt-only mode will create an illusion of successful
> > > initialization and set the wrong expectation for how the application will
> > > behave.
> > > 
> > 
> > Hi,
> > 
> > Thanks for the explanation which even I also believe is logically perfect.
> > 
> > But since l3fwd-power is an old application and has many users around
> > which are currently using this app in interrupt only mode without giving
> > an extra argument. But suddenly they will start getting failure messages with
> > the new patchset.
> > 
> > My only intent with else condition was backward compatibility.
> > Or may be we can have more descriptive failure message, something like
> > "init_power_library failed, check manual for other modes".
> > 
> > Thanks
> > Harman
> > 
> > 
> 
> I think we can compormise on an informative log message suggesting to use
> interrupt mode. I'm not keen on reverting to previous buggy behavior :)
> 
Hi

I am not insisting to revert to previous behavior, I am just trying to
highlight some probable issues that many users might face as its an old
application.
Since many arm based soc might not be supporting frequency scaling, can
we add the following check as soon as the application starts, probe the
platform if it supports frequency scaling, if not automatically set the
mode to interrupt mode, something like:
if (access("/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor",
			F_OK))
	app_mode = APP_MODE_INTERRUPT;


Thanks
Harman

> > > -- 
> > > Thanks,
> > > Anatoly
> 
> 
> -- 
> Thanks,
> Anatoly


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