[PATCH v2 0/2] send tlb_remove_table_smp_sync IPI only to necessary CPUs

Peter Zijlstra peterz at infradead.org
Wed Jun 21 17:43:37 AEST 2023

On Tue, Jun 20, 2023 at 05:46:16PM +0300, Yair Podemsky wrote:
> Currently the tlb_remove_table_smp_sync IPI is sent to all CPUs
> indiscriminately, this causes unnecessary work and delays notable in
> real-time use-cases and isolated cpus.
> By limiting the IPI to only be sent to cpus referencing the effected
> mm.
> a config to differentiate architectures that support mm_cpumask from
> those that don't will allow safe usage of this feature.
> changes from -v1:
> - Previous version included a patch to only send the IPI to CPU's with
> context_tracking in the kernel space, this was removed due to race 
> condition concerns.
> - for archs that do not maintain mm_cpumask the mask used should be
>  cpu_online_mask (Peter Zijlstra).

Would it not be much better to fix the root cause? As per the last time,
there's patches that cure the thp abuse of this.

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