]> git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/commit
sparc64: fix and optimize irq distribution
authorHong H. Pham <hong.pham@windriver.com>
Thu, 4 Jun 2009 09:10:11 +0000 (02:10 -0700)
committerDavid S. Miller <davem@davemloft.net>
Tue, 16 Jun 2009 11:56:28 +0000 (04:56 -0700)
commit280ff97494e0fef4124bee5c52e39b23a18dd283
treee906ca3c5e0a6238882d181ab5b01fb3f40ba5df
parent4fd78a5f1edf62ab1ca3d23efee4a8a336edb2b6
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>
arch/sparc/kernel/Makefile
arch/sparc/kernel/cpumap.c [new file with mode: 0644]
arch/sparc/kernel/cpumap.h [new file with mode: 0644]
arch/sparc/kernel/irq_64.c
arch/sparc/kernel/smp_64.c