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    SubjectRe: [PATCH] removes filp_count_lock and changes nr_files type to atomic_t
    Eric Dumazet wrote:

    > Furthermore, a lazy sync would mean to change sysctl proc_handler for
    > "file-nr" to perform a synchronize before calling proc_dointvec, this
    > would be really obscure.

    I was only using your terminology (ie. the 'lazy' synch after the
    atomic is updated).

    Actually, a better idea would be to make a specific sysctl handler
    like Christoph said.

    Unless you can show some improvement, it would better not to introduce
    the racy hack (even if it is mostly harmless).

    >> Unless the fs people had a problem with that.
    >> And you may as well get rid of the atomic_inc_return which can be more
    >> expensive on some platforms and doesn't buy you much.
    >> atomic_inc;
    >> atomic_read;
    >> Should be enough if you don't care about lost updates here, yeah?
    > You mean :
    > atomic_inc(&counter);
    > lazeyvalue = atomic_read(&counter);
    > instead of
    > lazeyvalue = atomic_inc_return(&counter);


    > In fact I couldnt find one architecture where the later would be more
    > expensive.

    atomic_inc_return guarantees a memory barrier, while the former
    statements do not. I'm fairly sure it will be more expensive on
    a POWER5.

    SUSE Labs, Novell Inc.

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      Last update: 2005-08-26 03:20    [W:0.045 / U:28.592 seconds]
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