Messages in this thread | | | Date | Sun, 12 Mar 2023 13:25:24 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to MM CPUs |
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On Sun, 12 Mar 2023 10:09:45 +0200 Yair Podemsky <ypodemsk@redhat.com> 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, this patch will limit this IPI to > only be sent to cpus referencing the effected mm and are currently in > kernel space. > > ... > > --- a/mm/mmu_gather.c > +++ b/mm/mmu_gather.c > @@ -191,7 +192,15 @@ static void tlb_remove_table_smp_sync(void *arg) > /* Simply deliver the interrupt */ > } > > -void tlb_remove_table_sync_one(void) > +static bool cpu_in_kernel(int cpu, void *info) > +{ > + struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu); > + int statue = atomic_read(&ct->state);
Strange identifier. Should be "state"?
> + //will return true only for cpu's in kernel space
Please use /* */ style comments
And use "cpus" rather than "cpu's" - plural, not possessive.
> + return !(statue & CT_STATE_MASK);
Using
return state & CT_STATE_MASK == CONTEXT_KERNEL;
would more clearly express the intent.
> +}
And... surely this function is racy. ct->state can change value one nanosecond after cpu_in_kernel() reads it, so cpu_in_kernel()'s return value is now wrong?
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