Re: [PATCH] x86/apic: reduce cache line misses in __x2apic_send_IPI_mask()

[Peter Zijlstra]

On Wed, Oct 06, 2021 at 08:17:56PM -0700, Eric Dumazet wrote:
> +/* __x2apic_send_IPI_mask() possibly needs to read
> + * x86_cpu_to_logical_apicid for all online cpus in a sequential way.
> + * Using per cpu variable would cost one cache line per cpu.
> + */

Broken comment style..

> +static u32 x86_cpu_to_logical_apicid[NR_CPUS] __read_mostly;

NR_CPUS is really sad, could this at all be dynamically allocated? Say
in x2apic_cluster_probe() ?


Otherwise this looks very nice!