lkml.org 
[lkml]   [2012]   [Jun]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH V3] block: Mitigate lock unbalance caused by lock switching
    On 05/30/2012 08:28 AM, Tejun Heo wrote:
    > Hello,
    >
    > On Wed, May 30, 2012 at 3:28 PM, Asias He <asias@redhat.com> wrote:
    >>> Isn't the 'if' clause superfluous ? You could just do the assignment,
    >>> e.g.,
    >>>
    >>> + spin_lock_irq(lock);
    >>> + q->queue_lock =&q->__queue_lock;
    >>> + spin_unlock_irq(lock);
    >>
    >>
    >> Well, this saves a if clause but adds an unnecessary assignment if the lock
    >> is already internal lock.
    >
    > It's not hot path. Dirtying the cacheline there doesn't mean anything.
    > I don't really care either way but making optimization argument is
    > pretty silly here.

    And more importantly, dropping the if loses information as well. That's
    a lot more important than any misguided optimization attempts. So I
    agree, the if stays.

    --
    Jens Axboe



    \
     
     \ /
      Last update: 2012-06-01 13:01    [W:2.447 / U:0.384 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site