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

* Rik van Riel <riel@surriel.com> 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

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