Marc Zyngier (2): irqchip/gic-v3-its: Track LPI distribution on a per CPU basis irqchip/gic-v3-its: Balance initial LPI affinity across CPUs
drivers/irqchip/irq-gic-v3-its.c | 171 ++++++++++++++++++++++++++++++++------- 1 file changed, 144 insertions(+), 27 deletions(-)
From: Marc Zyngier maz@kernel.org
In order to improve the distribution of LPIs among CPUs, let start by tracking the number of LPIs assigned to CPUs, both for managed and non-managed interrupts (as separate counters).
Signed-off-by: Marc Zyngier maz@kernel.org Tested-by: John Garry john.garry@huawei.com Link: https://lore.kernel.org/r/20200515165752.121296-2-maz@kernel.org --- drivers/irqchip/irq-gic-v3-its.c | 49 +++++++++++++++++++++++++++++++++++++--- 1 file changed, 46 insertions(+), 3 deletions(-)
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c index 7a0adf6..f7b966f 100644 --- a/drivers/irqchip/irq-gic-v3-its.c +++ b/drivers/irqchip/irq-gic-v3-its.c @@ -176,6 +176,13 @@ static struct { int next_victim; } vpe_proxy;
+struct cpu_lpi_count { + atomic_t managed; + atomic_t unmanaged; +}; + +static DEFINE_PER_CPU(struct cpu_lpi_count, cpu_lpi_count); + static LIST_HEAD(its_nodes); static DEFINE_RAW_SPINLOCK(its_lock); static struct rdists *gic_rdists; @@ -1162,6 +1169,30 @@ static void its_unmask_irq(struct irq_data *d) lpi_update_config(d, 0, LPI_PROP_ENABLED); }
+static __maybe_unused u32 its_read_lpi_count(struct irq_data *d, int cpu) +{ + if (irqd_affinity_is_managed(d)) + return atomic_read(&per_cpu_ptr(&cpu_lpi_count, cpu)->managed); + + return atomic_read(&per_cpu_ptr(&cpu_lpi_count, cpu)->unmanaged); +} + +static void its_inc_lpi_count(struct irq_data *d, int cpu) +{ + if (irqd_affinity_is_managed(d)) + atomic_inc(&per_cpu_ptr(&cpu_lpi_count, cpu)->managed); + else + atomic_inc(&per_cpu_ptr(&cpu_lpi_count, cpu)->unmanaged); +} + +static void its_dec_lpi_count(struct irq_data *d, int cpu) +{ + if (irqd_affinity_is_managed(d)) + atomic_dec(&per_cpu_ptr(&cpu_lpi_count, cpu)->managed); + else + atomic_dec(&per_cpu_ptr(&cpu_lpi_count, cpu)->unmanaged); +} + static void its_irq_chip_eoi(struct irq_data *d) { irq_move_irq(d); @@ -1177,17 +1208,21 @@ static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val, struct its_device *its_dev = irq_data_get_irq_chip_data(d); struct its_collection *target_col; u32 id = its_get_event_id(d); + int prev_cpu;
/* A forwarded interrupt should use irq_set_vcpu_affinity */ if (irqd_is_forwarded_to_vcpu(d)) return -EINVAL;
+ prev_cpu = its_dev->event_map.col_map[id]; + its_dec_lpi_count(d, prev_cpu); + /* lpi cannot be routed to a redistributor that is on a foreign node */ if (its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144) { if (its_dev->its->numa_node >= 0) { cpu_mask = cpumask_of_node(its_dev->its->numa_node); if (!cpumask_intersects(mask_val, cpu_mask)) - return -EINVAL; + goto err; } }
@@ -1200,17 +1235,23 @@ static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val, }
if (cpu >= max_cpu) - return -EINVAL; + goto err;
/* don't set the affinity when the target cpu is same as current one */ - if (cpu != its_dev->event_map.col_map[id]) { + if (cpu != prev_cpu) { target_col = &its_dev->its->collections[cpu]; its_send_movi(its_dev, target_col, id); its_dev->event_map.col_map[id] = cpu; irq_data_update_effective_affinity(d, cpumask_of(cpu)); }
+ its_inc_lpi_count(d, cpu); + return IRQ_SET_MASK_OK_DONE; + +err: + its_inc_lpi_count(d, prev_cpu); + return -EINVAL; }
static u64 its_irq_get_msi_base(struct its_device *its_dev) @@ -2903,6 +2944,7 @@ static int its_irq_domain_activate(struct irq_domain *domain, cpu = cpumask_first(cpu_online_mask); }
+ its_inc_lpi_count(d, cpu); its_dev->event_map.col_map[event] = cpu; irq_data_update_effective_affinity(d, cpumask_of(cpu));
@@ -2917,6 +2959,7 @@ static void its_irq_domain_deactivate(struct irq_domain *domain, struct its_device *its_dev = irq_data_get_irq_chip_data(d); u32 event = its_get_event_id(d);
+ its_dec_lpi_count(d, its_dev->event_map.col_map[event]); /* Stop the delivery of interrupts */ its_send_discard(its_dev, event); }
From: Marc Zyngier maz@kernel.org
When mapping a LPI, the ITS driver picks the first possible affinity, which is in most cases CPU0, assuming that if that's not suitable, someone will come and set the affinity to something more interesting.
It apparently isn't the case, and people complain of poor performance when many interrupts are glued to the same CPU. So let's place the interrupts by finding the "least loaded" CPU (that is, the one that has the fewer LPIs mapped to it). So called 'managed' interrupts are an interesting case where the affinity is actually dictated by the kernel itself, and we should honor this.
Reported-by: John Garry john.garry@huawei.com Signed-off-by: Marc Zyngier maz@kernel.org Tested-by: John Garry john.garry@huawei.com Link: https://lore.kernel.org/r/1575642904-58295-1-git-send-email-john.garry@huawe... Link: https://lore.kernel.org/r/20200515165752.121296-3-maz@kernel.org --- drivers/irqchip/irq-gic-v3-its.c | 126 +++++++++++++++++++++++++++++++-------- 1 file changed, 100 insertions(+), 26 deletions(-)
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c index f7b966f..7147f2d 100644 --- a/drivers/irqchip/irq-gic-v3-its.c +++ b/drivers/irqchip/irq-gic-v3-its.c @@ -1199,16 +1199,105 @@ static void its_irq_chip_eoi(struct irq_data *d) irq_chip_eoi_parent(d); }
+static unsigned int cpumask_pick_least_loaded(struct irq_data *d, + const struct cpumask *cpu_mask) +{ + unsigned int cpu = nr_cpu_ids, tmp; + int count = S32_MAX; + + for_each_cpu(tmp, cpu_mask) { + int this_count = its_read_lpi_count(d, tmp); + if (this_count < count) { + cpu = tmp; + count = this_count; + } + } + + return cpu; +} + +/* + * As suggested by Thomas Gleixner in: + * https://lore.kernel.org/r/87h80q2aoc.fsf@nanos.tec.linutronix.de + */ +static int its_select_cpu(struct irq_data *d, + const struct cpumask *aff_mask) +{ + struct its_device *its_dev = irq_data_get_irq_chip_data(d); + cpumask_var_t tmpmask; + int cpu, node; + + if (!alloc_cpumask_var(&tmpmask, GFP_ATOMIC)) + return -ENOMEM; + + node = its_dev->its->numa_node; + + if (!irqd_affinity_is_managed(d)) { + /* First try the NUMA node */ + if (node != NUMA_NO_NODE) { + /* + * Try the intersection of the affinity mask and the + * node mask (and the online mask, just to be safe). + */ + cpumask_and(tmpmask, cpumask_of_node(node), aff_mask); + cpumask_and(tmpmask, tmpmask, cpu_online_mask); + + /* + * Ideally, we would check if the mask is empty, and + * try again on the full node here. + * + * But it turns out that the way ACPI describes the + * affinity for ITSs only deals about memory, and + * not target CPUs, so it cannot describe a single + * ITS placed next to two NUMA nodes. + * + * Instead, just fallback on the online mask. This + * diverges from Thomas' suggestion above. + */ + cpu = cpumask_pick_least_loaded(d, tmpmask); + if (cpu < nr_cpu_ids) + goto out; + + /* If we can't cross sockets, give up */ + if ((its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144)) + goto out; + + /* If the above failed, expand the search */ + } + + /* Try the intersection of the affinity and online masks */ + cpumask_and(tmpmask, aff_mask, cpu_online_mask); + + /* If that doesn't fly, the online mask is the last resort */ + if (cpumask_empty(tmpmask)) + cpumask_copy(tmpmask, cpu_online_mask); + + cpu = cpumask_pick_least_loaded(d, tmpmask); + } else { + cpumask_and(tmpmask, irq_data_get_affinity_mask(d), cpu_online_mask); + + /* If we cannot cross sockets, limit the search to that node */ + if ((its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144) && + node != NUMA_NO_NODE) + cpumask_and(tmpmask, tmpmask, cpumask_of_node(node)); + + cpu = cpumask_pick_least_loaded(d, tmpmask); + } +out: + free_cpumask_var(tmpmask); + + pr_debug("IRQ%d -> %*pbl CPU%d\n", d->irq, cpumask_pr_args(aff_mask), cpu); + return cpu; +} + static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val, bool force) { - unsigned int cpu; unsigned int max_cpu; - const struct cpumask *cpu_mask = cpu_online_mask; struct its_device *its_dev = irq_data_get_irq_chip_data(d); struct its_collection *target_col; u32 id = its_get_event_id(d); - int prev_cpu; + int cpu, prev_cpu;
/* A forwarded interrupt should use irq_set_vcpu_affinity */ if (irqd_is_forwarded_to_vcpu(d)) @@ -1217,16 +1306,11 @@ static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val, prev_cpu = its_dev->event_map.col_map[id]; its_dec_lpi_count(d, prev_cpu);
- /* lpi cannot be routed to a redistributor that is on a foreign node */ - if (its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144) { - if (its_dev->its->numa_node >= 0) { - cpu_mask = cpumask_of_node(its_dev->its->numa_node); - if (!cpumask_intersects(mask_val, cpu_mask)) - goto err; - } - } + if (!force) + cpu = its_select_cpu(d, mask_val); + else + cpu = cpumask_pick_least_loaded(d, mask_val);
- cpu = cpumask_any_and(mask_val, cpu_mask); max_cpu = nr_cpu_ids;
if (init_all_gicr) { @@ -1234,7 +1318,7 @@ static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val, max_cpu = nr_gicr; }
- if (cpu >= max_cpu) + if (cpu < 0 || cpu >= max_cpu) goto err;
/* don't set the affinity when the target cpu is same as current one */ @@ -2928,21 +3012,11 @@ static int its_irq_domain_activate(struct irq_domain *domain, { struct its_device *its_dev = irq_data_get_irq_chip_data(d); u32 event = its_get_event_id(d); - const struct cpumask *cpu_mask = cpu_online_mask; int cpu;
- /* get the cpu_mask of local node */ - if (its_dev->its->numa_node >= 0) - cpu_mask = cpumask_of_node(its_dev->its->numa_node); - - /* Bind the LPI to the first possible CPU */ - cpu = cpumask_first_and(cpu_mask, cpu_online_mask); - if (cpu >= nr_cpu_ids) { - if (its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144) - return -EINVAL; - - cpu = cpumask_first(cpu_online_mask); - } + cpu = its_select_cpu(d, cpu_online_mask); + if (cpu < 0 || cpu >= nr_cpu_ids) + return -EINVAL;
its_inc_lpi_count(d, cpu); its_dev->event_map.col_map[event] = cpu;
-
Zhang Changzhong