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x86/apic: Avoid useless scanning thru a cpumask in assign_irq_vector() 

In case of static vector allocation domains (i.e. flat) if all
vector numbers are exhausted, an attempt to assign a new vector
will lead to useless scans through all CPUs in the cpumask, even
though it is known that each new pass would fail. Make this
corner case less painful by letting report whether the vector
allocation domain depends on passed arguments or not and stop
scanning early.

The same could have been achived by introducing a static flag to
the apic operations. But let's allow vector_allocation_domain()
have more intelligence here and decide dynamically, in case we
would need it in the future.

Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/20120607131542.GE4759@dhcp-26-207.brq.redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Alexander Gordeev 2012-06-07 15:15:44 +02:00 committed by Ingo Molnar
parent 1bccd58bff
commit 8637e38aff
3 changed files with 16 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
arch/x86/include/asm/apic.h
View File

@ -306,7 +306,7 @@ 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);
bool (*vector_allocation_domain)(int cpu, struct cpumask *retmask);
void (*init_apic_ldr)(void);
void (*ioapic_phys_id_map)(physid_mask_t *phys_map, physid_mask_t *retmap);
@ -615,7 +615,7 @@ extern unsigned int
default_cpu_mask_to_apicid_and(const struct cpumask *cpumask,
const struct cpumask *andmask);
static inline void
static inline bool
flat_vector_allocation_domain(int cpu, struct cpumask *retmask)
{
/* Careful. Some cpus do not strictly honor the set of cpus
@ -628,12 +628,14 @@ flat_vector_allocation_domain(int cpu, struct cpumask *retmask)
*/
cpumask_clear(retmask);
cpumask_bits(retmask)[0] = APIC_ALL_CPUS;
return false;
}
static inline void
static inline bool
default_vector_allocation_domain(int cpu, struct cpumask *retmask)
{
cpumask_copy(retmask, cpumask_of(cpu));
return true;
}
static inline unsigned long default_check_apicid_used(physid_mask_t *map, int apicid)

3
arch/x86/kernel/apic/apic_noop.c
View File

@ -100,11 +100,12 @@ 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 bool noop_vector_allocation_domain(int cpu, struct cpumask *retmask)
{
if (cpu != 0)
pr_warning("APIC: Vector allocated for non-BSP cpu\n");
cpumask_copy(retmask, cpumask_of(cpu));
return true;
}
static u32 noop_apic_read(u32 reg)

12
arch/x86/kernel/apic/io_apic.c
View File

@ -1137,8 +1137,9 @@ __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask)
for_each_cpu_and(cpu, mask, cpu_online_mask) {
int new_cpu;
int vector, offset;
bool more_domains;
apic->vector_allocation_domain(cpu, tmp_mask);
more_domains = apic->vector_allocation_domain(cpu, tmp_mask);
if (cpumask_subset(tmp_mask, cfg->domain)) {
free_cpumask_var(tmp_mask);
@ -1153,8 +1154,13 @@ next:
offset = (offset + 1) % 16;
vector = FIRST_EXTERNAL_VECTOR + offset;
}
if (unlikely(current_vector == vector))
continue;
if (unlikely(current_vector == vector)) {
if (more_domains)
continue;
else
break;
}
if (test_bit(vector, used_vectors))
goto next;