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Date: Fri, 20 May 2011 13:42:02 GMT
From: tip-bot for Cyrill Gorcunov <gorcunov@...nvz.org>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
gorcunov@...nvz.org, suresh.b.siddha@...el.com, tglx@...utronix.de,
mingo@...e.hu
Subject: [tip:x86/apic] x86, x2apic: Minimize IPI register writes using cluster groups
Commit-ID: 9d0fa6c5f43f2d9c6966dcab7af96a717682fdec
Gitweb: http://git.kernel.org/tip/9d0fa6c5f43f2d9c6966dcab7af96a717682fdec
Author: Cyrill Gorcunov <gorcunov@...nvz.org>
AuthorDate: Thu, 19 May 2011 16:45:49 -0700
Committer: Ingo Molnar <mingo@...e.hu>
CommitDate: Fri, 20 May 2011 13:41:09 +0200
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@...nvz.org>
Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
Cc: steiner@....com
Cc: yinghai@...nel.org
Link: http://lkml.kernel.org/r/20110519234637.512271057@sbsiddha-MOBL3.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
arch/x86/kernel/apic/x2apic_cluster.c | 58 +++++++++++++++++++++++++--------
1 files changed, 44 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c
index 4b2bb13..4dfe936 100644
--- a/arch/x86/kernel/apic/x2apic_cluster.c
+++ b/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 *nfb, unsigned long action, void *hcpu)
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 *nfb, unsigned long action, void *hcpu)
__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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