Re: [PATCH 7/7] x86,switch_mm: skip atomic operations for init_mm

[Ingo Molnar]

* Rik van Riel <riel@xxxxxxxxxxx> wrote:

> +		/*
> +		 * Stop remote flushes for the previous mm.
> +		 * Skip the idle task; we never send init_mm TLB flushing IPIs,
> +		 * but the bitmap manipulation can cause cache line contention.
> +		 */
> +		if (real_prev != &init_mm) {
> +			VM_WARN_ON_ONCE(!cpumask_test_cpu(cpu,
> +						mm_cpumask(real_prev)));
> +			cpumask_clear_cpu(cpu, mm_cpumask(real_prev));

BTW., could this optimization be (safely) extended to all (or most) !task->mm 
kernel threads?

In particular softirq and threaded irq handlers could benefit greatly I suspect in 
certain networking intense workloads that happen to active them.

Thanks,

	Ingo