Messages in this thread Patch in this message | | | Date | Fri, 13 May 2011 11:04:53 -0700 | From | Suresh Siddha <> | Subject | [patch 4/5] x86, x2apic: Minimize IPI register writes using cluster groups |
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From: Cyrill Gorcunov <gorcunov@openvz.org> Subjct: x86, x2apic: Minimize IPI register writes using cluster groups
In the case of x2apic cluster mode we can group IPI register writes based on the cluster group instead of individual per-cpu destination messages.
This reduces the apic register writes and reduces the amount of IPI messages (in the best case we can reduce it by a factor of 16).
With this change, the cost of flush_tlb_others(), with the flush tlb IPI being sent from a cpu in the socket-1 to all the logical cpus in socket-2 (on a Westmere-EX system that has 20 logical cpus in a socket) is 3x times better now (compared to the former 'send one-by-one' algorithm).
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> --- arch/x86/kernel/apic/x2apic_cluster.c | 58 +++++++++++++++++++++++++--------- 1 file changed, 44 insertions(+), 14 deletions(-)
Index: linux-2.6-tip/arch/x86/kernel/apic/x2apic_cluster.c =================================================================== --- linux-2.6-tip.orig/arch/x86/kernel/apic/x2apic_cluster.c +++ linux-2.6-tip/arch/x86/kernel/apic/x2apic_cluster.c @@ -5,6 +5,7 @@ #include <linux/ctype.h> #include <linux/init.h> #include <linux/dmar.h> +#include <linux/cpu.h> #include <asm/smp.h> #include <asm/apic.h> @@ -12,6 +13,7 @@ static DEFINE_PER_CPU(u32, x86_cpu_to_logical_apicid); static DEFINE_PER_CPU(cpumask_var_t, cpus_in_cluster); +static DEFINE_PER_CPU(cpumask_var_t, ipi_mask); static int x2apic_acpi_madt_oem_check(char *oem_id, char *oem_table_id) { @@ -54,30 +56,52 @@ static inline u32 x2apic_cluster(int cpu return per_cpu(x86_cpu_to_logical_apicid, cpu) >> 16; } -/* - * for now, we send the IPI's one by one in the cpumask. - * TBD: Based on the cpu mask, we can send the IPI's to the cluster group - * at once. We have 16 cpu's in a cluster. This will minimize IPI register - * writes. - */ static void __x2apic_send_IPI_mask(const struct cpumask *mask, int vector, int apic_dest) { - unsigned long query_cpu; - unsigned long this_cpu; + struct cpumask *cpus_in_cluster_ptr; + struct cpumask *ipi_mask_ptr; + unsigned int cpu, this_cpu; unsigned long flags; + u32 dest; x2apic_wrmsr_fence(); local_irq_save(flags); this_cpu = smp_processor_id(); - for_each_cpu(query_cpu, mask) { - if (apic_dest == APIC_DEST_ALLBUT && query_cpu == this_cpu) + + /* + * We are to modify mask, so we need an own copy + * and be sure it's manipulated with irq off. + */ + ipi_mask_ptr = __raw_get_cpu_var(ipi_mask); + cpumask_copy(ipi_mask_ptr, mask); + + /* + * The idea is to send one IPI per cluster. + */ + for_each_cpu(cpu, ipi_mask_ptr) { + unsigned long i; + + cpus_in_cluster_ptr = per_cpu(cpus_in_cluster, cpu); + dest = 0; + + /* Collect cpus in cluster. */ + for_each_cpu_and(i, ipi_mask_ptr, cpus_in_cluster_ptr) { + if (apic_dest == APIC_DEST_ALLINC || i != this_cpu) + dest |= per_cpu(x86_cpu_to_logical_apicid, i); + } + + if (!dest) continue; - __x2apic_send_IPI_dest( - per_cpu(x86_cpu_to_logical_apicid, query_cpu), - vector, apic->dest_logical); + + __x2apic_send_IPI_dest(dest, vector, apic->dest_logical); + /* + * Cluster sibling cpus should be discared now so + * we would not send IPI them second time. + */ + cpumask_andnot(ipi_mask_ptr, ipi_mask_ptr, cpus_in_cluster_ptr); } local_irq_restore(flags); @@ -198,6 +222,10 @@ update_clusterinfo(struct notifier_block if (!zalloc_cpumask_var(&per_cpu(cpus_in_cluster, this_cpu), GFP_KERNEL)) { err = -ENOMEM; + } else if (!zalloc_cpumask_var(&per_cpu(ipi_mask, this_cpu), + GFP_KERNEL)) { + free_cpumask_var(per_cpu(cpus_in_cluster, this_cpu)); + err = -ENOMEM; } break; case CPU_UP_CANCELED: @@ -210,6 +238,7 @@ update_clusterinfo(struct notifier_block __cpu_clear(cpu, per_cpu(cpus_in_cluster, this_cpu)); } free_cpumask_var(per_cpu(cpus_in_cluster, this_cpu)); + free_cpumask_var(per_cpu(ipi_mask, this_cpu)); break; } @@ -225,8 +254,9 @@ static int x2apic_init_cpu_notifier(void int cpu = smp_processor_id(); zalloc_cpumask_var(&per_cpu(cpus_in_cluster, cpu), GFP_KERNEL); + zalloc_cpumask_var(&per_cpu(ipi_mask, cpu), GFP_KERNEL); - BUG_ON(!per_cpu(cpus_in_cluster, cpu)); + BUG_ON(!per_cpu(cpus_in_cluster, cpu) || !per_cpu(ipi_mask, cpu)); __cpu_set(cpu, per_cpu(cpus_in_cluster, cpu)); register_hotcpu_notifier(&x2apic_cpu_notifier);
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