On Thu, Jun 29, 2017 at 08:53:22AM -0700, Andy Lutomirski wrote:
> +static void choose_new_asid(struct mm_struct *next, u64 next_tlb_gen,
> + u16 *new_asid, bool *need_flush)
> +{
> + u16 asid;
> +
> + if (!static_cpu_has(X86_FEATURE_PCID)) {
> + *new_asid = 0;
> + *need_flush = true;
> + return;
> + }
> +
> + for (asid = 0; asid < TLB_NR_DYN_ASIDS; asid++) {
> + if (this_cpu_read(cpu_tlbstate.ctxs[asid].ctx_id) !=
> + next->context.ctx_id)
> + continue;
> +
> + *new_asid = asid;
> + *need_flush = (this_cpu_read(cpu_tlbstate.ctxs[asid].tlb_gen) <
> + next_tlb_gen);
> + return;
> + }
> +
> + /*
> + * We don't currently own an ASID slot on this CPU.
> + * Allocate a slot.
> + */
> + *new_asid = this_cpu_add_return(cpu_tlbstate.next_asid, 1) - 1;
So this basically RR the ASID slots. Have you tried slightly more
complex replacement policies like CLOCK ?
> + if (*new_asid >= TLB_NR_DYN_ASIDS) {
> + *new_asid = 0;
> + this_cpu_write(cpu_tlbstate.next_asid, 1);
> + }
> + *need_flush = true;
> +}
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