Re: task switch from net-rx to idle when there is napi processing to be done

[Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>]

Hello,

On Tue, Jan 24, 2012 at 06:39:34PM -0800, Venkat Subbiah wrote:
> In the process of debugging a napi ethernet driver performance
> issue, what I am noticing is
> 
> 1. While the driver is in the middle of a napi packet processing
> loop, there is a task switch from
> sirq-net-rx to idle even though there is pending napi processing to be done.
I didn't check your logs below, but maybe this is related to the default
settings in /proc/sys/kernel/sched_rt_period_us and
/proc/sys/kernel/sched_rt_runtime_us? That is 0.05s per second is
reserved for non-RT tasks tasks such that a run-away realtime process
will not lock up the machine.

To verify that, try

	echo -1 > /proc/sys/kernel/sched_rt_runtime_us

.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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