Fwd: is it possible to liimit the softirq re entrance times

Fwd: is it possible to liimit the softirq re entrance times

[vichy]

after I tracing softirq flow in ARM platform, I have some colusion like below:
1. softirq is running at the end of any irq context, when irq is eabled.
2. as long as any Hard irq happen, softirq can be interrupt and reentrant

My question are:
1. in __do_sofiq, there is a jiffies setting to make sure the whole
softirq will not took to long.
But in my case is there any many hard irq happen like below

                        trace_softirq_entry(vec_nr);    ------a
                        h->action(h);
                        trace_softirq_exit(vec_nr);      ---------b

from lttng, I see there 100 interrupt happen from entry to exit.

is there kernel config or module parameter to let me down grade the
hard irq count from 100  --> 80 or 90 and event can controlled me.
I don't mean I control the count of hard irq, but I found this softirq
is interrupt by 80 times.
then I will not enable_irq until I finished the job.

if no, isn't it possible to make starvation in above a and b?

really appreciate ur kind help,

Fwd: is it possible to liimit the softirq re entrance times

[Valdis.Kletnieks at vt.edu]

On Fri, 21 Aug 2015 01:12:10 +0800, vichy said:
>
> if no, isn't it possible to make starvation in above a and b?

Operating systems have to make design choices.

You run with IRQs disabled for too long, you can starve other IRQs waiting
for service.

You run with them mostly enabled, the one handler can get starved by a
screaming interrupt (or a large number of devices all generating interrupts).

Choosing wisely is required - some devices are low-speed with large buffers,
so don't care if it takes a while to service them.  Meanwhile, others are
extremely latency-sensitive.  So in general, each driver gets designed to
fit the device's tolerance for delay.
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