On 01/25/2012 12:55 AM, Uwe Kleine-König wrote:
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
.
Thanks for you response. That was it. Setting this to -1 does the expected.
Then I tried playing with these settings and set
/proc/sys/kernel/sched_rt_runtime_us to 95000
/proc/sys/kernel/sched_rt_period_us to 100000
And even with the switch from sirq-net-rx to idle happens every seconds
and stays in idle for 0.05 seconds. Are they any restrictions on what
these can be set to? I guess these setting may not be reasonable. I did
verify by doing a cat of these files and read back the expected values.
Then I tried
/proc/sys/kernel/sched_rt_period_us to 1000000
/proc/sys/kernel/sched_rt_runtime_us to 980000
Even here the idle is for 0.05 seconds
Best regards
Uwe
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