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Message-ID: <680fadba-9104-3914-5175-e207fd3d9246@intel.com>
Date: Wed, 21 Jun 2023 10:42:16 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Yair Podemsky <ypodemsk@...hat.com>, mtosatti@...hat.com,
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Subject: Re: [PATCH v2 2/2] mm/mmu_gather: send tlb_remove_table_smp_sync IPI
only to MM CPUs
On 6/20/23 07:46, Yair Podemsky wrote:
> -void tlb_remove_table_sync_one(void)
> +#ifdef CONFIG_ARCH_HAS_CPUMASK_BITS
> +#define REMOVE_TABLE_IPI_MASK mm_cpumask(mm)
> +#else
> +#define REMOVE_TABLE_IPI_MASK cpu_online_mask
> +#endif /* CONFIG_ARCH_HAS_CPUMASK_BITS */
> +
> +void tlb_remove_table_sync_one(struct mm_struct *mm)
> {
> /*
> * This isn't an RCU grace period and hence the page-tables cannot be
> @@ -200,7 +206,8 @@ void tlb_remove_table_sync_one(void)
> * It is however sufficient for software page-table walkers that rely on
> * IRQ disabling.
> */
> - smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
> + on_each_cpu_mask(REMOVE_TABLE_IPI_MASK, tlb_remove_table_smp_sync,
> + NULL, true);
> }
That "REMOVE_TABLE_IPI_MASK" thing is pretty confusing. It *looks* like
a constant. It does *NOT* look at all like it consumes 'mm'. Worst
case, just create a local variable:
if (IS_ENABLED(CONFIG_ARCH_HAS_CPUMASK_BITS))
ipi_mask = mm_cpumask(mm);
else
ipi_mask = cpu_online_mask;
on_each_cpu_mask(ipi_mask, ...);
That's a billion times more clear and it'll compile down to the same thing.
I do think the CONFIG_ARCH_HAS_CPUMASK_BITS naming is also pretty
confusing, but I don't have any better suggestions. Maybe something
with "MM_CPUMASK" in it?
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