From 8ffe4e61c06a48324cfd97f1199bb9838acce2f2 Mon Sep 17 00:00:00 2001 From: Dou Liyang Date: Sun, 9 Sep 2018 01:58:37 +0800 Subject: irq/matrix: Split out the CPU selection code into a helper Linux finds the CPU which has the lowest vector allocation count to spread out the non managed interrupts across the possible target CPUs, but does not do so for managed interrupts. Split out the CPU selection code into a helper function for reuse. No functional change. Signed-off-by: Dou Liyang Signed-off-by: Thomas Gleixner Cc: hpa@zytor.com Link: https://lkml.kernel.org/r/20180908175838.14450-1-dou_liyang@163.com --- kernel/irq/matrix.c | 65 +++++++++++++++++++++++++++++++---------------------- 1 file changed, 38 insertions(+), 27 deletions(-) diff --git a/kernel/irq/matrix.c b/kernel/irq/matrix.c index 5092494bf261..67768bbe736e 100644 --- a/kernel/irq/matrix.c +++ b/kernel/irq/matrix.c @@ -124,6 +124,27 @@ static unsigned int matrix_alloc_area(struct irq_matrix *m, struct cpumap *cm, return area; } +/* Find the best CPU which has the lowest vector allocation count */ +static unsigned int matrix_find_best_cpu(struct irq_matrix *m, + const struct cpumask *msk) +{ + unsigned int cpu, best_cpu, maxavl = 0; + struct cpumap *cm; + + best_cpu = UINT_MAX; + + for_each_cpu(cpu, msk) { + cm = per_cpu_ptr(m->maps, cpu); + + if (!cm->online || cm->available <= maxavl) + continue; + + best_cpu = cpu; + maxavl = cm->available; + } + return best_cpu; +} + /** * irq_matrix_assign_system - Assign system wide entry in the matrix * @m: Matrix pointer @@ -322,37 +343,27 @@ void irq_matrix_remove_reserved(struct irq_matrix *m) int irq_matrix_alloc(struct irq_matrix *m, const struct cpumask *msk, bool reserved, unsigned int *mapped_cpu) { - unsigned int cpu, best_cpu, maxavl = 0; + unsigned int cpu, bit; struct cpumap *cm; - unsigned int bit; - best_cpu = UINT_MAX; - for_each_cpu(cpu, msk) { - cm = per_cpu_ptr(m->maps, cpu); - - if (!cm->online || cm->available <= maxavl) - continue; + cpu = matrix_find_best_cpu(m, msk); + if (cpu == UINT_MAX) + return -ENOSPC; - best_cpu = cpu; - maxavl = cm->available; - } + cm = per_cpu_ptr(m->maps, cpu); + bit = matrix_alloc_area(m, cm, 1, false); + if (bit >= m->alloc_end) + return -ENOSPC; + cm->allocated++; + cm->available--; + m->total_allocated++; + m->global_available--; + if (reserved) + m->global_reserved--; + *mapped_cpu = cpu; + trace_irq_matrix_alloc(bit, cpu, m, cm); + return bit; - if (maxavl) { - cm = per_cpu_ptr(m->maps, best_cpu); - bit = matrix_alloc_area(m, cm, 1, false); - if (bit < m->alloc_end) { - cm->allocated++; - cm->available--; - m->total_allocated++; - m->global_available--; - if (reserved) - m->global_reserved--; - *mapped_cpu = best_cpu; - trace_irq_matrix_alloc(bit, best_cpu, m, cm); - return bit; - } - } - return -ENOSPC; } /** -- cgit v1.2.3 From 76f99ae5b54d48430d1f0c5512a84da0ff9761e0 Mon Sep 17 00:00:00 2001 From: Dou Liyang Date: Sun, 9 Sep 2018 01:58:38 +0800 Subject: irq/matrix: Spread managed interrupts on allocation Linux spreads out the non managed interrupt across the possible target CPUs to avoid vector space exhaustion. Managed interrupts are treated differently, as for them the vectors are reserved (with guarantee) when the interrupt descriptors are initialized. When the interrupt is requested a real vector is assigned. The assignment logic uses the first CPU in the affinity mask for assignment. If the interrupt has more than one CPU in the affinity mask, which happens when a multi queue device has less queues than CPUs, then doing the same search as for non managed interrupts makes sense as it puts the interrupt on the least interrupt plagued CPU. For single CPU affine vectors that's obviously a NOOP. Restructre the matrix allocation code so it does the 'best CPU' search, add the sanity check for an empty affinity mask and adapt the call site in the x86 vector management code. [ tglx: Added the empty mask check to the core and improved change log ] Signed-off-by: Dou Liyang Signed-off-by: Thomas Gleixner Cc: hpa@zytor.com Link: https://lkml.kernel.org/r/20180908175838.14450-2-dou_liyang@163.com --- arch/x86/kernel/apic/vector.c | 9 ++++----- include/linux/irq.h | 3 ++- kernel/irq/matrix.c | 17 ++++++++++++++--- 3 files changed, 20 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c index 7654febd5102..652e7ffa9b9d 100644 --- a/arch/x86/kernel/apic/vector.c +++ b/arch/x86/kernel/apic/vector.c @@ -313,14 +313,13 @@ assign_managed_vector(struct irq_data *irqd, const struct cpumask *dest) struct apic_chip_data *apicd = apic_chip_data(irqd); int vector, cpu; - cpumask_and(vector_searchmask, vector_searchmask, affmsk); - cpu = cpumask_first(vector_searchmask); - if (cpu >= nr_cpu_ids) - return -EINVAL; + cpumask_and(vector_searchmask, dest, affmsk); + /* set_affinity might call here for nothing */ if (apicd->vector && cpumask_test_cpu(apicd->cpu, vector_searchmask)) return 0; - vector = irq_matrix_alloc_managed(vector_matrix, cpu); + vector = irq_matrix_alloc_managed(vector_matrix, vector_searchmask, + &cpu); trace_vector_alloc_managed(irqd->irq, vector, vector); if (vector < 0) return vector; diff --git a/include/linux/irq.h b/include/linux/irq.h index 201de12a9957..c9bffda04a45 100644 --- a/include/linux/irq.h +++ b/include/linux/irq.h @@ -1151,7 +1151,8 @@ void irq_matrix_offline(struct irq_matrix *m); void irq_matrix_assign_system(struct irq_matrix *m, unsigned int bit, bool replace); int irq_matrix_reserve_managed(struct irq_matrix *m, const struct cpumask *msk); void irq_matrix_remove_managed(struct irq_matrix *m, const struct cpumask *msk); -int irq_matrix_alloc_managed(struct irq_matrix *m, unsigned int cpu); +int irq_matrix_alloc_managed(struct irq_matrix *m, const struct cpumask *msk, + unsigned int *mapped_cpu); void irq_matrix_reserve(struct irq_matrix *m); void irq_matrix_remove_reserved(struct irq_matrix *m); int irq_matrix_alloc(struct irq_matrix *m, const struct cpumask *msk, diff --git a/kernel/irq/matrix.c b/kernel/irq/matrix.c index 67768bbe736e..6e6d467f3dec 100644 --- a/kernel/irq/matrix.c +++ b/kernel/irq/matrix.c @@ -260,11 +260,21 @@ void irq_matrix_remove_managed(struct irq_matrix *m, const struct cpumask *msk) * @m: Matrix pointer * @cpu: On which CPU the interrupt should be allocated */ -int irq_matrix_alloc_managed(struct irq_matrix *m, unsigned int cpu) +int irq_matrix_alloc_managed(struct irq_matrix *m, const struct cpumask *msk, + unsigned int *mapped_cpu) { - struct cpumap *cm = per_cpu_ptr(m->maps, cpu); - unsigned int bit, end = m->alloc_end; + unsigned int bit, cpu, end = m->alloc_end; + struct cpumap *cm; + + if (cpumask_empty(msk)) + return -EINVAL; + cpu = matrix_find_best_cpu(m, msk); + if (cpu == UINT_MAX) + return -ENOSPC; + + cm = per_cpu_ptr(m->maps, cpu); + end = m->alloc_end; /* Get managed bit which are not allocated */ bitmap_andnot(m->scratch_map, cm->managed_map, cm->alloc_map, end); bit = find_first_bit(m->scratch_map, end); @@ -273,6 +283,7 @@ int irq_matrix_alloc_managed(struct irq_matrix *m, unsigned int cpu) set_bit(bit, cm->alloc_map); cm->allocated++; m->total_allocated++; + *mapped_cpu = cpu; trace_irq_matrix_alloc_managed(bit, cpu, m, cm); return bit; } -- cgit v1.2.3