src/patches/suse-2.6.27.39/patches.drivers/fcoe-improved-load-balancing-i.diff

   1 From: Vasu Dev <vasu.dev@intel.com>
   2 Subject: [FcOE] improved load balancing in rx path
   3 References: bnc #459142
   4
   5 Currently incoming frame exchange id ANDing with total number of bits
   6 in online CPU bits mask, resulted only at most two CPUs selection in
   7 rx path, so instead used online CPU bits mask to direct incoming frame
   8 to a all cpus for better load balancing.
   9
  10 Added code to default to first CPU in case selected CPU is offline or
  11 its rx thread not present.
  12
  13 Signed-off-by: Vasu Dev <vasu.dev@intel.com>
  14 Acked-by: Bernhard Walle <bwalle@suse.de>
  15 ---
  16
  17  drivers/scsi/fcoe/libfcoe.c |   13 +++++++------
  18  1 file changed, 7 insertions(+), 6 deletions(-)
  19
  20
  21 --- a/drivers/scsi/fcoe/libfcoe.c
  22 +++ b/drivers/scsi/fcoe/libfcoe.c
  23 @@ -230,13 +230,14 @@ int fcoe_rcv(struct sk_buff *skb, struct
  24         cpu_idx = 0;
  25  #ifdef CONFIG_SMP
  26         /*
  27 -        * The exchange ID are ANDed with num of online CPUs,
  28 -        * so that will have the least lock contention in
  29 -        * handling the exchange. if there is no thread
  30 -        * for a given idx then use first online cpu.
  31 +        * The incoming frame exchange id(oxid) is ANDed with num of online
  32 +        * cpu bits to get cpu_idx and then this cpu_idx is used for selecting
  33 +        * a per cpu kernel thread from fcoe_percpu. In case the cpu is
  34 +        * offline or no kernel thread for derived cpu_idx then cpu_idx is
  35 +        * initialize to first online cpu index.
  36          */
  37 -       cpu_idx = oxid & (num_online_cpus() >> 1);
  38 -       if (fcoe_percpu[cpu_idx] == NULL)
  39 +       cpu_idx = oxid & (num_online_cpus() - 1);
  40 +       if (!fcoe_percpu[cpu_idx] || !cpu_online(cpu_idx))
  41                 cpu_idx = first_cpu(cpu_online_map);
  42  #endif
  43         fps = fcoe_percpu[cpu_idx];