lkml.org 
[lkml]   [2009]   [Oct]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [this_cpu_xx V5 19/19] SLUB: Experimental new fastpath w/o interrupt disable
    * Christoph Lameter (cl@linux-foundation.org) wrote:
    > On Wed, 7 Oct 2009, Mathieu Desnoyers wrote:
    >
    > > Usually, when preemption is disabled, the scheduler restrain from
    > > executing. *Now the important point*: the criterion that bounds the
    > > maximum amount of time before the scheduler will re-check for pending
    > > preemption is when preempt_enable() will re-activate preemption.
    >
    > Which creates additional overhead in the allocator.
    >

    Which we like to keep as low as possible, I agree.

    > > But because you run preempt_enable with interrupts off, the scheduler
    > > check is not done. And it's not done when interrupts are re-activated
    > > neither.
    >
    > Ok so we should be moving the preempt_enable after the irq enable. Then we
    > will call into the scheduler at the end of the slow path. This may add
    > significantly more overhead that we had before when we simply disabled
    > and enabled interrupts...
    >

    You are already calling the scheduler when ending the _fast_ path. I
    don't see the problem with calling it when you end the slow path
    execution.

    Mathieu

    --
    Mathieu Desnoyers
    OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


    \
     
     \ /
      Last update: 2009-10-07 17:29    [W:0.024 / U:119.096 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site