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    SubjectRe: [PATCH v6 00/11] locking/rwsem: Rework rwsem-xadd & enable new rwsem features
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    On 10/11/2017 02:48 PM, Peter Zijlstra wrote:
    > On Wed, Oct 11, 2017 at 02:01:51PM -0400, Waiman Long wrote:
    >> # of Patches Reader Writer
    >> Applied Locking Rate Locking Rate
    >> ------------ ------------ ------------
    >> 0 5,155/ 5,155/ 5,155 5,154/248,852/346,281
    >> 7 5,696/ 5,697/ 5,698 113,500/215,826/320,872
    >> 8 4,827/ 5,047/ 5,215 4,826/176,797/284,069
    >> 9 211,276/ 509,712/1,134,007 4,894/221,839/246,818
    >> 11 884,513/1,043,989/1,252,533 9,604/ 11,105/ 25,225
    >>
    >> It can be seen that rwsem changes from writer-preferring to
    >> reader-preferring.
    > A bit radically so, you almost starve the writers there.

    Yes, almost, but the lock handoff code will make sure that it won't
    actually get starved. That is why I added aggressive reader lock
    stealing after the lock handoff code.

    Cheers,
    Longman

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