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authorHong H. Pham <hong.pham@windriver.com>2009-06-04 02:10:11 -0700
committerDavid S. Miller <davem@davemloft.net>2009-06-16 04:56:28 -0700
commit280ff97494e0fef4124bee5c52e39b23a18dd283 (patch)
treee906ca3c5e0a6238882d181ab5b01fb3f40ba5df /arch/sparc/kernel/irq_64.c
parent4fd78a5f1edf62ab1ca3d23efee4a8a336edb2b6 (diff)
sparc64: fix and optimize irq distribution
irq_choose_cpu() should compare the affinity mask against cpu_online_map rather than CPU_MASK_ALL, since irq_select_affinity() sets the interrupt's affinity mask to cpu_online_map "and" CPU_MASK_ALL (which ends up being just cpu_online_map). The mask comparison in irq_choose_cpu() will always fail since the two masks are not the same. So the CPU chosen is the first CPU in the intersection of cpu_online_map and CPU_MASK_ALL, which is always CPU0. That means all interrupts are reassigned to CPU0... Distributing interrupts to CPUs in a linearly increasing round robin fashion is not optimal for the UltraSPARC T1/T2. Also, the irq_rover in irq_choose_cpu() causes an interrupt to be assigned to a different processor each time the interrupt is allocated and released. This may lead to an unbalanced distribution over time. A static mapping of interrupts to processors is done to optimize and balance interrupt distribution. For the T1/T2, interrupts are spread to different cores first, and then to strands within a core. The following is some benchmarks showing the effects of interrupt distribution on a T2. The test was done with iperf using a pair of T5220 boxes, each with a 10GBe NIU (XAUI) connected back to back. TCP | Stock Linear RR IRQ Optimized IRQ Streams | 2.6.30-rc5 Distribution Distribution | GBits/sec GBits/sec GBits/sec --------+----------------------------------------- 1 0.839 0.862 0.868 8 1.16 4.96 5.88 16 1.15 6.40 8.04 100 1.09 7.28 8.68 Signed-off-by: Hong H. Pham <hong.pham@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/sparc/kernel/irq_64.c')
-rw-r--r--arch/sparc/kernel/irq_64.c29
1 files changed, 4 insertions, 25 deletions
diff --git a/arch/sparc/kernel/irq_64.c b/arch/sparc/kernel/irq_64.c
index e5e78f9cfc95..bd075054942b 100644
--- a/arch/sparc/kernel/irq_64.c
+++ b/arch/sparc/kernel/irq_64.c
@@ -45,6 +45,7 @@
#include <asm/cacheflush.h>
#include "entry.h"
+#include "cpumap.h"
#define NUM_IVECS (IMAP_INR + 1)
@@ -256,35 +257,13 @@ static int irq_choose_cpu(unsigned int virt_irq)
int cpuid;
cpumask_copy(&mask, irq_desc[virt_irq].affinity);
- if (cpus_equal(mask, CPU_MASK_ALL)) {
- static int irq_rover;
- static DEFINE_SPINLOCK(irq_rover_lock);
- unsigned long flags;
-
- /* Round-robin distribution... */
- do_round_robin:
- spin_lock_irqsave(&irq_rover_lock, flags);
-
- while (!cpu_online(irq_rover)) {
- if (++irq_rover >= nr_cpu_ids)
- irq_rover = 0;
- }
- cpuid = irq_rover;
- do {
- if (++irq_rover >= nr_cpu_ids)
- irq_rover = 0;
- } while (!cpu_online(irq_rover));
-
- spin_unlock_irqrestore(&irq_rover_lock, flags);
+ if (cpus_equal(mask, cpu_online_map)) {
+ cpuid = map_to_cpu(virt_irq);
} else {
cpumask_t tmp;
cpus_and(tmp, cpu_online_map, mask);
-
- if (cpus_empty(tmp))
- goto do_round_robin;
-
- cpuid = first_cpu(tmp);
+ cpuid = cpus_empty(tmp) ? map_to_cpu(virt_irq) : first_cpu(tmp);
}
return cpuid;