path: root/arch/sparc/kernel/smp_64.c
diff options
authorHong H. Pham <>2009-06-04 02:10:11 -0700
committerDavid S. Miller <>2009-06-16 04:56:28 -0700
commit280ff97494e0fef4124bee5c52e39b23a18dd283 (patch)
treee906ca3c5e0a6238882d181ab5b01fb3f40ba5df /arch/sparc/kernel/smp_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 <> Signed-off-by: David S. Miller <>
Diffstat (limited to 'arch/sparc/kernel/smp_64.c')
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index 1de47d2169c8..cfb3d06058ff 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -48,6 +48,8 @@
#include <asm/ldc.h>
#include <asm/hypervisor.h>
+#include "cpumap.h"
int sparc64_multi_core __read_mostly;
DEFINE_PER_CPU(cpumask_t, cpu_sibling_map) = CPU_MASK_NONE;
@@ -1314,6 +1316,8 @@ int __cpu_disable(void)
cpu_clear(cpu, cpu_online_map);
+ cpu_map_rebuild();
return 0;