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    [SCSI] fcoe: Amends previous patch, Round-robin based selection of CPU for... · 29bdd2bb
    Kiran Patil 提交于
    [SCSI] fcoe: Amends previous patch, Round-robin based selection of CPU for post processing of incoming request for FCoE target
    
    Problem: Selection of RX queue on target is based on RX-ID. FCoE used
    8 Net Rx queues.  HW post the packets based on rx_id %
    num_rx_queue. Due to this has based filtering, only one CPU is busy
    servicing incoming request including post-processing of incoming
    request. This is gating factor because
    
    1. Only one CPU is utilized 100% while others CPUs are not used at all.
    
    2. CPU which received request assign "sequence' by selecting exchange
       from per CPU pool (num_ddp_context / num_online_cpus,
       approxi.). Due to which if if rate of incoming request is higher
       than rate of servicing request, existing code path end of sending
       "BUSY" response (SAM_STAT_BUSY because unable to allocate
       exchange).
    
    Fix: Fan-out incoming request to all other CPUs excluding the CPU
    which is receiving all incoiming request. This path also addresses,
    selecting same CPU based on rx_id from received frame for completion
    of the request such as "releasing exchange to the per CPU Pool". This
    fix is applicable for FCoE target since initiator code path already
    takes care of selecting CPU to complete post-processing of request
    once OX_ID is assigned.
    
    Notes: N/A
    
    Dependencines: N/A
    Signed-off-by: NKiran Patil <kiran.patil@intel.com>
    Signed-off-by: NRobert Love <robert.w.love@intel.com>
    Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>
    29bdd2bb
fcoe.c 69.0 KB