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Date: Thu, 21 Jun 2012 11:04:51 +0200
From: Alexander Gordeev <agordeev@...hat.com>
To: Suresh Siddha <suresh.b.siddha@...el.com>
Cc: Ingo Molnar <mingo@...nel.org>, yinghai@...nel.org,
linux-kernel@...r.kernel.org, x86@...nel.org, gorcunov@...nvz.org
Subject: Re: [PATCH 2/2] x86, x2apic: limit the vector reservation to the
user specified mask
On Tue, Jun 19, 2012 at 04:43:31PM -0700, Suresh Siddha wrote:
> For the x2apic cluster mode, vector for an interrupt is currently reserved on
> all the cpu's that are part of the x2apic cluster. But the interrupts will
> be routed only to the cluster (derived from the first cpu in the mask) members
> specified in the mask. So there is no need to reserve the vector in the unused
> cluster members.
>
> Modify __assign_irq_vector() to reserve the vectors based on the user
> specified irq destination mask and the corresponding vector domain specified
> by the apic driver.
>
> Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
> ---
> arch/x86/include/asm/apic.h | 14 +++++++++---
> arch/x86/kernel/apic/apic_noop.c | 5 +++-
> arch/x86/kernel/apic/io_apic.c | 36 ++++++++++++++++++++++-----------
> arch/x86/kernel/apic/x2apic_cluster.c | 8 ++++--
> 4 files changed, 43 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
> index b37fa12..7746acb 100644
> --- a/arch/x86/include/asm/apic.h
> +++ b/arch/x86/include/asm/apic.h
> @@ -306,7 +306,9 @@ struct apic {
> unsigned long (*check_apicid_used)(physid_mask_t *map, int apicid);
> unsigned long (*check_apicid_present)(int apicid);
>
> - void (*vector_allocation_domain)(int cpu, struct cpumask *retmask);
> + void (*vector_allocation_domain)(const struct cpumask *mask,
> + struct cpumask *retmask,
> + const struct cpumask *prevmask);
> void (*init_apic_ldr)(void);
>
> void (*ioapic_phys_id_map)(physid_mask_t *phys_map, physid_mask_t *retmap);
> @@ -615,7 +617,9 @@ default_cpu_mask_to_apicid_and(const struct cpumask *cpumask,
> unsigned int *apicid);
>
> static inline void
> -flat_vector_allocation_domain(int cpu, struct cpumask *retmask)
> +flat_vector_allocation_domain(const struct cpumask *mask,
> + struct cpumask *retmask,
> + const struct cpumask *prevmask)
> {
> /* Careful. Some cpus do not strictly honor the set of cpus
> * specified in the interrupt destination when using lowest
> @@ -630,9 +634,11 @@ flat_vector_allocation_domain(int cpu, struct cpumask *retmask)
> }
>
> static inline void
> -default_vector_allocation_domain(int cpu, struct cpumask *retmask)
> +default_vector_allocation_domain(const struct cpumask *mask,
> + struct cpumask *retmask,
> + const struct cpumask *prevmask)
> {
> - cpumask_copy(retmask, cpumask_of(cpu));
> + cpumask_copy(retmask, cpumask_of(cpumask_first(retmask)));
> }
>
> static inline unsigned long default_check_apicid_used(physid_mask_t *map, int apicid)
> diff --git a/arch/x86/kernel/apic/apic_noop.c b/arch/x86/kernel/apic/apic_noop.c
> index 08c337b..847ece1 100644
> --- a/arch/x86/kernel/apic/apic_noop.c
> +++ b/arch/x86/kernel/apic/apic_noop.c
> @@ -100,8 +100,11 @@ static unsigned long noop_check_apicid_present(int bit)
> return physid_isset(bit, phys_cpu_present_map);
> }
>
> -static void noop_vector_allocation_domain(int cpu, struct cpumask *retmask)
> +static void noop_vector_allocation_domain(const struct cpumask *mask,
> + struct cpumask *retmask,
> + const struct cpumask *prevmask)
> {
> + int cpu = cpumask_first(retmask);
> if (cpu != 0)
> pr_warning("APIC: Vector allocated for non-BSP cpu\n");
> cpumask_copy(retmask, cpumask_of(cpu));
> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
> index 7a945f8..0a55eb8 100644
> --- a/arch/x86/kernel/apic/io_apic.c
> +++ b/arch/x86/kernel/apic/io_apic.c
> @@ -1097,6 +1097,22 @@ void unlock_vector_lock(void)
> raw_spin_unlock(&vector_lock);
> }
>
> +/*
> + * New cpu mask using the vector is a subset of the current in use mask.
> + * So cleanup the vector allocation for the members that are not used anymore.
> + */
> +static inline int
> +cleanup_unused_subset(struct cpumask *mask, struct irq_cfg *cfg)
> +{
> + if (!cpumask_equal(mask, cfg->domain)) {
> + cpumask_andnot(cfg->old_domain, cfg->domain, mask);
> + cfg->move_in_progress = 1;
> + cpumask_and(cfg->domain, cfg->domain, mask);
> + }
> + free_cpumask_var(mask);
> + return 0;
> +}
> +
Adding to 1st Yinghai's comment, this function does not appear needed at all...
> static int
> __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask)
> {
> @@ -1126,10 +1142,9 @@ __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask)
> old_vector = cfg->vector;
> if (old_vector) {
> cpumask_and(tmp_mask, mask, cpu_online_mask);
> - if (cpumask_subset(tmp_mask, cfg->domain)) {
> - free_cpumask_var(tmp_mask);
> - return 0;
> - }
> + apic->vector_allocation_domain(mask, tmp_mask, cfg->domain);
> + if (cpumask_subset(tmp_mask, cfg->domain))
> + return cleanup_unused_subset(tmp_mask, cfg);
...but if you decide to leave cleanup_unused_subset() then cpumask_subset()
check is better to move inside the function while free_cpumask_var() move
out.
> }
>
> /* Only try and allocate irqs on cpus that are present */
> @@ -1137,15 +1152,12 @@ __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask)
> cpumask_clear(cfg->old_domain);
> cpu = cpumask_first_and(mask, cpu_online_mask);
> while (cpu < nr_cpu_ids) {
> - int new_cpu;
> - int vector, offset;
> + int new_cpu, vector, offset;
>
> - apic->vector_allocation_domain(cpu, tmp_mask);
> -
> - if (cpumask_subset(tmp_mask, cfg->domain)) {
> - free_cpumask_var(tmp_mask);
> - return 0;
> - }
> + cpumask_copy(tmp_mask, cpumask_of(cpu));
> + apic->vector_allocation_domain(mask, tmp_mask, cfg->domain);
I might be missing the point.. in the two lines above you copy a cpumask to
tmp_mask, then scan it in vector_allocation_domain() just to find the cpu
which you already know. Why not just pass cpu rather then cpumask_of(cpu)?
> + if (cpumask_subset(tmp_mask, cfg->domain))
> + return cleanup_unused_subset(tmp_mask, cfg);
>
> vector = current_vector;
> offset = current_offset;
> diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c
> index b5d889b..4d49512 100644
> --- a/arch/x86/kernel/apic/x2apic_cluster.c
> +++ b/arch/x86/kernel/apic/x2apic_cluster.c
> @@ -212,10 +212,12 @@ static int x2apic_cluster_probe(void)
> /*
> * Each x2apic cluster is an allocation domain.
> */
> -static void cluster_vector_allocation_domain(int cpu, struct cpumask *retmask)
> +static void cluster_vector_allocation_domain(const struct cpumask *mask,
> + struct cpumask *retmask,
> + const struct cpumask *prevmask)
> {
> - cpumask_clear(retmask);
> - cpumask_copy(retmask, per_cpu(cpus_in_cluster, cpu));
> + int cpu = cpumask_first(retmask);
> + cpumask_and(retmask, mask, per_cpu(cpus_in_cluster, cpu));
> }
>
> static struct apic apic_x2apic_cluster = {
> --
> 1.7.6.5
>
--
Regards,
Alexander Gordeev
agordeev@...hat.com
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