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SubjectRe: [PATCH RFC tip/core/rcu 5/5] rcu: Limit expedited helping to every 10 ms or every 4th GP
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On Tue, Jun 30, 2015 at 11:48 PM, Paul E. McKenney
<paulmck@linux.vnet.ibm.com> wrote:
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
> kernel/rcu/tree.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 308b6acb4260..247aa1120c4c 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3505,10 +3505,19 @@ void synchronize_sched_expedited(void)
> !atomic_read(&rsp->expedited_need_qs));
>
> rcu_exp_gp_seq_end(rsp);
> - mutex_unlock(&rnp->exp_funnel_mutex);
> smp_mb(); /* ensure subsequent action seen after grace period. */
> - if (rsp->gp_kthread && rcu_gp_in_progress(rsp))
> - wake_up(&rsp->gp_wq);
> + if (rsp->gp_kthread && rcu_gp_in_progress(rsp)) {
> + static unsigned long nextgp;
> + static unsigned long nextjiffy;
> +
> + if (time_after_eq(jiffies, nextgp) ||
> + ULONG_CMP_GE(rsp->gpnum, nextgp)) {
> + nextgp = rsp->gpnum + 4;
> + nextjiffy = jiffies + 10;

Do you want 10 ticks or 10 ms (as stated in title) ?

> + wake_up(&rsp->gp_wq);
> + }
> + }
> + mutex_unlock(&rnp->exp_funnel_mutex);
>
> put_online_cpus();
> }
> --
> 1.8.1.5
>


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