From 280ff97494e0fef4124bee5c52e39b23a18dd283 Mon Sep 17 00:00:00 2001 From: "Hong H. Pham" Date: Thu, 4 Jun 2009 02:10:11 -0700 Subject: 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 --- arch/sparc/kernel/cpumap.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) create mode 100644 arch/sparc/kernel/cpumap.h (limited to 'arch/sparc/kernel/cpumap.h') diff --git a/arch/sparc/kernel/cpumap.h b/arch/sparc/kernel/cpumap.h new file mode 100644 index 00000000000..e639880ab86 --- /dev/null +++ b/arch/sparc/kernel/cpumap.h @@ -0,0 +1,16 @@ +#ifndef _CPUMAP_H +#define _CPUMAP_H + +#ifdef CONFIG_SMP +extern void cpu_map_rebuild(void); +extern int map_to_cpu(unsigned int index); +#define cpu_map_init() cpu_map_rebuild() +#else +#define cpu_map_init() do {} while (0) +static inline int map_to_cpu(unsigned int index) +{ + return raw_smp_processor_id(); +} +#endif + +#endif -- cgit v1.2.3