On Fri, Jun 01, 2018 at 11:03:09AM +0900, Byungchul Park wrote:
> Currently, the range of jiffies_till_{first,next}_fqs are checked and
> adjusted on and on in the loop of rcu_gp_kthread on runtime.
>
> However, it's enough to check them only when setting them, not every
> time in the loop. So make them handled on a setting time via sysfs.
>
> Signed-off-by: Byungchul Park <byungchul.p...@lge.com>
Applied for further review and testing, thank you!
Thanx, Paul
> ---
> kernel/rcu/tree.c | 45 ++++++++++++++++++++++++++++++++-------------
> 1 file changed, 32 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 4e96761..eb54d7d 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -518,8 +518,38 @@ void rcu_all_qs(void)
> static ulong jiffies_till_next_fqs = ULONG_MAX;
> static bool rcu_kick_kthreads;
>
> -module_param(jiffies_till_first_fqs, ulong, 0644);
> -module_param(jiffies_till_next_fqs, ulong, 0644);
> +static int param_set_first_fqs_jiffies(const char *val, const struct
> kernel_param *kp)
> +{
> + ulong j;
> + int ret = kstrtoul(val, 0, &j);
> +
> + if (!ret)
> + WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : j);
> + return ret;
> +}
> +
> +static int param_set_next_fqs_jiffies(const char *val, const struct
> kernel_param *kp)
> +{
> + ulong j;
> + int ret = kstrtoul(val, 0, &j);
> +
> + if (!ret)
> + WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : (j ?: 1));
> + return ret;
> +}
> +
> +static struct kernel_param_ops first_fqs_jiffies_ops = {
> + .set = param_set_first_fqs_jiffies,
> + .get = param_get_ulong,
> +};
> +
> +static struct kernel_param_ops next_fqs_jiffies_ops = {
> + .set = param_set_next_fqs_jiffies,
> + .get = param_get_ulong,
> +};
> +
> +module_param_cb(jiffies_till_first_fqs, &first_fqs_jiffies_ops,
> &jiffies_till_first_fqs, 0644);
> +module_param_cb(jiffies_till_next_fqs, &next_fqs_jiffies_ops,
> &jiffies_till_next_fqs, 0644);
> module_param(rcu_kick_kthreads, bool, 0644);
>
> /*
> @@ -2129,10 +2159,6 @@ static int __noreturn rcu_gp_kthread(void *arg)
> /* Handle quiescent-state forcing. */
> first_gp_fqs = true;
> j = jiffies_till_first_fqs;
> - if (j > HZ) {
> - j = HZ;
> - jiffies_till_first_fqs = HZ;
> - }
> ret = 0;
> for (;;) {
> if (!ret) {
> @@ -2167,13 +2193,6 @@ static int __noreturn rcu_gp_kthread(void *arg)
> WRITE_ONCE(rsp->gp_activity, jiffies);
> ret = 0; /* Force full wait till next FQS. */
> j = jiffies_till_next_fqs;
> - if (j > HZ) {
> - j = HZ;
> - jiffies_till_next_fqs = HZ;
> - } else if (j < 1) {
> - j = 1;
> - jiffies_till_next_fqs = 1;
> - }
> } else {
> /* Deal with stray signal. */
> cond_resched_tasks_rcu_qs();
> --
> 1.9.1
>
