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    SubjectRe: [patch 7/11] net: Use bigrefs for net_device.refcount
    On Tue, Sep 13, 2005 at 08:27:52PM +0200, Eric Dumazet wrote:
    > Ravikiran G Thirumalai a écrit :
    >
    > Hum...
    >
    > Did you tried to place refcnt/netdev_refcnt in a separate cache line than
    > queue_lock ? I got good results too...
    >
    > > /* device queue lock */
    > > spinlock_t queue_lock;
    > > /* Number of references to this device */
    > > - atomic_t refcnt;
    > > + struct bigref netdev_refcnt ____cacheline_aligned_in_smp ;
    > > /* delayed register/unregister */
    > > struct list_head todo_list;
    > > /* device name hash chain */
    >
    > Every time a cpu take the queue_lock spinlock, it exclusively gets one
    > cache line. If another cpu try to access netdev_refcnt, it has to grab this
    > cache line (even if properely per_cpu designed, there is still one shared
    > field). In fact the whole struct net_device should be re-ordered for
    > SMP/NUMA performance.

    I agree. Maybe placing the queue_lock in a different cacheline is the
    right approach?

    Thanks,
    Kiran
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