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| author | Hong H. Pham <hong.pham@windriver.com> | 2009-06-04 02:10:11 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2009-06-16 04:56:28 -0700 |
| commit | 280ff97494e0fef4124bee5c52e39b23a18dd283 (patch) | |
| tree | e906ca3c5e0a6238882d181ab5b01fb3f40ba5df /arch/sparc/kernel/cpumap.h | |
| parent | 4fd78a5f1edf62ab1ca3d23efee4a8a336edb2b6 (diff) | |
| download | linux-280ff97494e0fef4124bee5c52e39b23a18dd283.tar.bz2 | |
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/cpumap.h')
| -rw-r--r-- | arch/sparc/kernel/cpumap.h | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/arch/sparc/kernel/cpumap.h b/arch/sparc/kernel/cpumap.h new file mode 100644 index 000000000000..e639880ab864 --- /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 |