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    SubjectRe: 8-CPU (SMP) #s for lockfree rtcache
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    On Tue, 2002-05-28 at 17:34, Andi Kleen wrote:
    > And gain tons of new atomic_incs and decs everywhere in the process?
    > I would prefer RCU.

    RCU is a great way to make sure people get module unloading *wrong*. It
    has to be simple for the driver authors. The odd locked operation on
    things like open() of a device file is not a performance issue, not
    remotely.

    Lots of people write drivers, many of them not SMP kernel locking gurus
    who have time to understand RCU and when they can or cannot sleep, and
    what happens if their unload is pre-empted and RCU is in use. The kernel
    core has to provide a clean easy interface. The network code is a superb
    example of this. All the hard thinking is done outside of the driver, at
    least unless you choose to join in that thinking to get the last scraps
    of performance.

    Alan

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