• David Daney's avatar
    MIPS: Optimize spinlocks. · 500c2e1f
    David Daney authored
    The current locking mechanism uses a ll/sc sequence to release a
    spinlock.  This is slower than a wmb() followed by a store to unlock.
    
    The branching forward to .subsection 2 on sc failure slows down the
    contended case.  So we get rid of that part too.
    
    Since we are now working on naturally aligned u16 values, we can get
    rid of a masking operation as the LHU already does the right thing.
    The ANDI are reversed for better scheduling on multi-issue CPUs
    
    On a 12 CPU 750MHz Octeon cn5750 this patch improves ipv4 UDP packet
    forwarding rates from 3.58*10^6 PPS to 3.99*10^6 PPS, or about 11%.
    Signed-off-by: default avatarDavid Daney <ddaney@caviumnetworks.com>
    To: linux-mips@linux-mips.org
    Patchwork: http://patchwork.linux-mips.org/patch/937/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
    500c2e1f
barrier.h 4.89 KB