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Date: Mon, 18 Jun 2012 11:17:41 +0200
From: Alexander Gordeev <agordeev@...hat.com>
To: Suresh Siddha <suresh.b.siddha@...el.com>
Cc: yinghai@...nel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
gorcunov@...nvz.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 1/2] x86, irq: update irq_cfg domain unless the new
affinity is a subset of the current domain
On Fri, Jun 15, 2012 at 05:25:20PM -0700, Suresh Siddha wrote:
> On Wed, 2012-06-06 at 16:02 -0700, Suresh Siddha wrote:
> Ok, here is a quick version of the patch doing the first option I
> mentioned above. Reserve the vectors based on the irq destination mask
> and the corresponding vector domain, rather than reserving the vector on
> all the cpu's for the theoretical domain (which is an x2apic cluster).
Suresh,
I would suggest to go further and generalize your idea and introduce something
like compare_domains() instead sub_domain flag. This would help us to keep/let
__assign_irq_vector() be more generic and hide domains treating logic in
drivers.
Also, this would fix a previous subtle condition introduced with previous
commit 332afa6 ("x86/irq: Update irq_cfg domain unless the new affinity is a
subset of the current domain") when a change of affinity mask could trigger
unnecessary move of vector in case new and old masks intersect, but the new
mask is not a subset of the old one.
The patch is just to clarify the idea, neither tested nor even compiled.
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index eec240e..fcca995 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -306,7 +306,10 @@ struct apic {
unsigned long (*check_apicid_used)(physid_mask_t *map, int apicid);
unsigned long (*check_apicid_present)(int apicid);
- bool (*vector_allocation_domain)(int cpu, struct cpumask *retmask);
+ bool (*vector_allocation_domain)(int cpu,
+ const struct cpumask *mask,
+ struct cpumask *retmask);
+ int (*compare_domains)(const struct cpumask *, const struct cpumask *);
void (*init_apic_ldr)(void);
void (*ioapic_phys_id_map)(physid_mask_t *phys_map, physid_mask_t *retmap);
@@ -615,7 +618,9 @@ default_cpu_mask_to_apicid_and(const struct cpumask *cpumask,
unsigned int *apicid);
static inline bool
-flat_vector_allocation_domain(int cpu, struct cpumask *retmask)
+flat_vector_allocation_domain(int cpu,
+ const struct cpumask *mask,
+ struct cpumask *retmask)
{
/* Careful. Some cpus do not strictly honor the set of cpus
* specified in the interrupt destination when using lowest
@@ -630,13 +635,33 @@ flat_vector_allocation_domain(int cpu, struct cpumask *retmask)
return false;
}
+static inline int
+flat_compare_domains(const struct cpumask *domain1,
+ const struct cpumask *domain2)
+{
+ if (cpumask_subset(domain1, domain2))
+ return 0;
+ return 1;
+}
+
static inline bool
-default_vector_allocation_domain(int cpu, struct cpumask *retmask)
+default_vector_allocation_domain(int cpu,
+ const struct cpumask *mask,
+ struct cpumask *retmask)
{
cpumask_copy(retmask, cpumask_of(cpu));
return true;
}
+static inline int
+default_compare_domains(const struct cpumask *domain1,
+ const struct cpumask *domain2)
+{
+ if (cpumask_intersects(domain1, domain2))
+ return 0;
+ return 1;
+}
+
static inline unsigned long default_check_apicid_used(physid_mask_t *map, int apicid)
{
return physid_isset(apicid, *map);
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 0540f08..88cafc8 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1126,7 +1126,7 @@ __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)) {
+ if (!apic->compare_domains(tmp_mask, cfg->domain)) {
free_cpumask_var(tmp_mask);
return 0;
}
@@ -1138,47 +1138,50 @@ __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask)
int new_cpu;
int vector, offset;
bool more_domains;
+ int cmp_domains;
- more_domains = apic->vector_allocation_domain(cpu, tmp_mask);
+ more = apic->vector_allocation_domain(cpu, mask, tmp_mask);
+ cmp = apic->compare_domains(tmp_mask, cfg->domain);
- if (cpumask_subset(tmp_mask, cfg->domain)) {
- free_cpumask_var(tmp_mask);
- return 0;
- }
-
- vector = current_vector;
- offset = current_offset;
+ if (cmp < 0) {
+ cpumask_andnot(cfg->old_domain, cfg->domain, tmp_mask);
+ cfg->move_in_progress = 1;
+ cpumask_and(cfg->domain, cfg->domain, tmp_mask);
+ } else if (cmp > 0) {
+ vector = current_vector;
+ offset = current_offset;
next:
- vector += 16;
- if (vector >= first_system_vector) {
- offset = (offset + 1) % 16;
- vector = FIRST_EXTERNAL_VECTOR + offset;
- }
-
- if (unlikely(current_vector == vector)) {
- if (more_domains)
- continue;
- else
- break;
- }
+ vector += 16;
+ if (vector >= first_system_vector) {
+ offset = (offset + 1) % 16;
+ vector = FIRST_EXTERNAL_VECTOR + offset;
+ }
- if (test_bit(vector, used_vectors))
- goto next;
+ if (unlikely(current_vector == vector)) {
+ if (more)
+ continue;
+ else
+ break;
+ }
- for_each_cpu_and(new_cpu, tmp_mask, cpu_online_mask)
- if (per_cpu(vector_irq, new_cpu)[vector] != -1)
+ if (test_bit(vector, used_vectors))
goto next;
- /* Found one! */
- current_vector = vector;
- current_offset = offset;
- if (old_vector) {
- cfg->move_in_progress = 1;
- cpumask_copy(cfg->old_domain, cfg->domain);
+
+ for_each_cpu_and(new_cpu, tmp_mask, cpu_online_mask)
+ if (per_cpu(vector_irq, new_cpu)[vector] != -1)
+ goto next;
+ /* Found one! */
+ current_vector = vector;
+ current_offset = offset;
+ if (old_vector) {
+ cfg->move_in_progress = 1;
+ cpumask_copy(cfg->old_domain, cfg->domain);
+ }
+ for_each_cpu_and(new_cpu, tmp_mask, cpu_online_mask)
+ per_cpu(vector_irq, new_cpu)[vector] = irq;
+ cfg->vector = vector;
+ cpumask_copy(cfg->domain, tmp_mask);
}
- for_each_cpu_and(new_cpu, tmp_mask, cpu_online_mask)
- per_cpu(vector_irq, new_cpu)[vector] = irq;
- cfg->vector = vector;
- cpumask_copy(cfg->domain, tmp_mask);
err = 0;
break;
}
diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c
index 943d03f..090c69e 100644
--- a/arch/x86/kernel/apic/x2apic_cluster.c
+++ b/arch/x86/kernel/apic/x2apic_cluster.c
@@ -212,13 +212,24 @@ static int x2apic_cluster_probe(void)
/*
* Each x2apic cluster is an allocation domain.
*/
-static bool cluster_vector_allocation_domain(int cpu, struct cpumask *retmask)
+static bool cluster_vector_allocation_domain(int cpu,
+ const struct cpumask *mask,
+ struct cpumask *retmask)
{
- cpumask_clear(retmask);
- cpumask_copy(retmask, per_cpu(cpus_in_cluster, cpu));
+ cpumask_and(retmask, mask, per_cpu(cpus_in_cluster, cpu));
return true;
}
+static int cluster_compare_domains(const struct cpumask *domain1,
+ const struct cpumask *domain2)
+{
+ if (cpumask_subset(domain1, domain2))
+ return -1;
+ if (cpumask_equal(domain1, domain2))
+ return 0;
+ return 1;
+}
+
static struct apic apic_x2apic_cluster = {
.name = "cluster x2apic",
@@ -237,6 +248,7 @@ static struct apic apic_x2apic_cluster = {
.check_apicid_present = NULL,
.vector_allocation_domain = cluster_vector_allocation_domain,
+ .compare_domains = cluster_compare_domains,
.init_apic_ldr = init_x2apic_ldr,
.ioapic_phys_id_map = NULL,
diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2apic_phys.c
index e03a1e1..24511a9 100644
--- a/arch/x86/kernel/apic/x2apic_phys.c
+++ b/arch/x86/kernel/apic/x2apic_phys.c
@@ -106,6 +106,7 @@ static struct apic apic_x2apic_phys = {
.check_apicid_present = NULL,
.vector_allocation_domain = default_vector_allocation_domain,
+ .compare_domains = default_compare_domains,
.init_apic_ldr = init_x2apic_ldr,
.ioapic_phys_id_map = NULL,
--
Regards,
Alexander Gordeev
agordeev@...hat.com
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