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Date: Sat, 19 May 2012 13:53:36 -0700
From: Yinghai Lu <yinghai@...nel.org>
To: Alexander Gordeev <agordeev@...hat.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
Suresh Siddha <suresh.b.siddha@...el.com>,
Cyrill Gorcunov <gorcunov@...nvz.org>
Subject: Re: [PATCH 2/3] x86: x2apic/cluster: Make use of lowest priority
delivery mode
On Fri, May 18, 2012 at 3:26 AM, Alexander Gordeev <agordeev@...hat.com> wrote:
> Currently x2APIC in logical destination mode delivers interrupts to a
> single CPU, no matter how many CPUs were specified in the destination
> cpumask.
>
> This fix enables delivery of interrupts to multiple CPUs by bit-ORing
> Logical IDs of destination CPUs that have matching Cluster ID.
>
> Because only one cluster could be specified in a message destination
> address, the destination cpumask is tried for a cluster that contains
> maximum number of CPUs matching this cpumask. The CPUs in this cluster
> are selected to receive the interrupts while all other CPUs (in the
> cpumask) are ignored.
>
> Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
> ---
> arch/x86/include/asm/x2apic.h | 9 --
> arch/x86/kernel/apic/x2apic_cluster.c | 140 +++++++++++++++++++++++++++++----
> arch/x86/kernel/apic/x2apic_phys.c | 9 ++-
> 3 files changed, 131 insertions(+), 27 deletions(-)
>
> diff --git a/arch/x86/include/asm/x2apic.h b/arch/x86/include/asm/x2apic.h
> index 92e54ab..7a5a832 100644
> --- a/arch/x86/include/asm/x2apic.h
> +++ b/arch/x86/include/asm/x2apic.h
> @@ -28,15 +28,6 @@ static int x2apic_apic_id_registered(void)
> return 1;
> }
>
> -/*
> - * For now each logical cpu is in its own vector allocation domain.
> - */
> -static void x2apic_vector_allocation_domain(int cpu, struct cpumask *retmask)
> -{
> - cpumask_clear(retmask);
> - cpumask_set_cpu(cpu, retmask);
> -}
> -
> static void
> __x2apic_send_IPI_dest(unsigned int apicid, int vector, unsigned int dest)
> {
> diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c
> index 8f012b2..f8fa4c4 100644
> --- a/arch/x86/kernel/apic/x2apic_cluster.c
> +++ b/arch/x86/kernel/apic/x2apic_cluster.c
> @@ -96,36 +96,142 @@ static void x2apic_send_IPI_all(int vector)
> __x2apic_send_IPI_mask(cpu_online_mask, vector, APIC_DEST_ALLINC);
> }
>
> +static inline unsigned int
> +__x2apic_cluster_to_apicid(int cpu_in_cluster, const struct cpumask *cpumask)
> +{
> + unsigned int apicid = 0;
> + int cpu;
> +
> + for_each_cpu_and(cpu, per_cpu(cpus_in_cluster, cpu_in_cluster), cpumask)
> + apicid |= per_cpu(x86_cpu_to_logical_apicid, cpu);
> +
> + return apicid;
> +}
> +
> +static int
> +__x2apic_cpu_mask_to_apicid(const struct cpumask *cpumask, unsigned int *apicid)
> +{
> + int ret = 0;
> + int cpu, heaviest;
> + unsigned int weight, max_weight;
> + cpumask_var_t target_cpus, cluster_cpus;
> +
> + if (unlikely(!alloc_cpumask_var(&target_cpus, GFP_ATOMIC))) {
> + ret = -ENOMEM;
> + goto out;
> + }
> + if (unlikely(!alloc_cpumask_var(&cluster_cpus, GFP_ATOMIC))) {
> + ret = -ENOMEM;
> + goto out_free_target_cpus;
> + }
> +
> + cpumask_and(target_cpus, cpumask, cpu_online_mask);
> + max_weight = 0;
> +
> + for_each_cpu(cpu, target_cpus) {
> + cpumask_and(cluster_cpus, per_cpu(cpus_in_cluster, cpu), cpumask);
> +
> + weight = cpumask_weight(cluster_cpus);
> + if (weight > max_weight) {
> + max_weight = weight;
> + heaviest = cpu;
> + }
> +
> + cpumask_andnot(target_cpus, target_cpus, cluster_cpus);
> + }
> +
> + if (!max_weight) {
> + ret = -EINVAL;
> + goto out_free_cluster_cpus;
> + }
> +
> + *apicid = __x2apic_cluster_to_apicid(heaviest, cpumask);
> +
> +out_free_cluster_cpus:
> + free_cpumask_var(cluster_cpus);
> +out_free_target_cpus:
> + free_cpumask_var(target_cpus);
> +out:
> + return ret;
> +}
> +
> static unsigned int x2apic_cpu_mask_to_apicid(const struct cpumask *cpumask)
> {
> - /*
> - * We're using fixed IRQ delivery, can only return one logical APIC ID.
> - * May as well be the first.
> - */
> - int cpu = cpumask_first(cpumask);
> + int err;
> + int cpu;
> + unsigned int apicid;
>
> - if ((unsigned)cpu < nr_cpu_ids)
> - return per_cpu(x86_cpu_to_logical_apicid, cpu);
> - else
> - return BAD_APICID;
> + err = __x2apic_cpu_mask_to_apicid(cpumask, &apicid);
> + WARN_ON(err);
> +
> + if (!err)
> + return apicid;
> +
> + if (err == -ENOMEM) {
> + for_each_cpu(cpu, cpumask) {
> + if (cpumask_test_cpu(cpu, cpu_online_mask))
> + break;
> + }
> + if (cpu < nr_cpu_ids)
> + return __x2apic_cluster_to_apicid(cpu, cpumask);
> + }
> +
> + return BAD_APICID;
> }
>
> static unsigned int
> x2apic_cpu_mask_to_apicid_and(const struct cpumask *cpumask,
> const struct cpumask *andmask)
> {
> - int cpu;
> + int err;
> + int cpu, first_cpu;
> + unsigned int apicid;
> + cpumask_var_t target_cpus;
> +
> + if (likely(alloc_cpumask_var(&target_cpus, GFP_ATOMIC))) {
> + cpumask_and(target_cpus, cpumask, andmask);
> +
> + err = __x2apic_cpu_mask_to_apicid(target_cpus, &apicid);
> +
> + free_cpumask_var(target_cpus);
> +
> + if (!err)
> + return apicid;
> + } else {
> + err = -ENOMEM;
> + }
> +
> + WARN_ON(err);
> +
> + if (err != -ENOMEM)
> + return 0;
> +
> + apicid = 0;
> + first_cpu = nr_cpu_ids;
>
> - /*
> - * We're using fixed IRQ delivery, can only return one logical APIC ID.
> - * May as well be the first.
> - */
> for_each_cpu_and(cpu, cpumask, andmask) {
> - if (cpumask_test_cpu(cpu, cpu_online_mask))
> + if (cpumask_test_cpu(cpu, cpu_online_mask)) {
> + first_cpu = cpu;
> break;
> + }
> + }
> +
> + if (first_cpu < nr_cpu_ids) {
> + for_each_cpu_and(cpu, per_cpu(cpus_in_cluster, first_cpu),
> + cpumask) {
> + if (!cpumask_test_cpu(cpu, andmask))
> + continue;
> + apicid |= per_cpu(x86_cpu_to_logical_apicid, cpu);
> + }
> }
>
> - return per_cpu(x86_cpu_to_logical_apicid, cpu);
> + return apicid;
> +}
> +
> +static void
> +x2apic_cluster_vector_allocation_domain(int cpu, struct cpumask *retmask)
> +{
> + cpumask_copy(retmask, cpu_possible_mask);
why not using per_cpu(cpus_in_cluster, cpu) instead?
also you may add one per cpu var like x86_cpu_to_logical_cluster_apicid.
Yinghai
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