Allow debugfs override of sched_tick_max_deferment in order to ease finding/fixing the remaining issues with full nohz.
The value to be written is in jiffies, and -1 means the max deferment is disabled (scheduler_tick_max_deferment() returns KTIME_MAX.)
Cc: Frederic Weisbecker fweisbec@gmail.com Signed-off-by: Kevin Hilman khilman@linaro.org --- kernel/sched/core.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5ac63c9..4b1fe3e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2175,6 +2175,8 @@ void scheduler_tick(void) }
#ifdef CONFIG_NO_HZ_FULL +static u32 sched_tick_max_deferment = HZ; + /** * scheduler_tick_max_deferment * @@ -2193,13 +2195,25 @@ u64 scheduler_tick_max_deferment(void) struct rq *rq = this_rq(); unsigned long next, now = ACCESS_ONCE(jiffies);
- next = rq->last_sched_tick + HZ; + if (sched_tick_max_deferment == -1) + return KTIME_MAX; + + next = rq->last_sched_tick + sched_tick_max_deferment;
if (time_before_eq(next, now)) return 0;
return jiffies_to_usecs(next - now) * NSEC_PER_USEC; } + +static __init int sched_nohz_full_init_debug(void) +{ + debugfs_create_u32("sched_tick_max_deferment", 0644, NULL, + &sched_tick_max_deferment); + + return 0; +} +late_initcall(sched_nohz_full_init_debug); #endif
notrace unsigned long get_parent_ip(unsigned long addr)
The conversion of the max deferment from usecs to nsecs can easily overflow on platforms where a long is 32-bits. To fix, cast the usecs value to u64 before multiplying by NSECS_PER_USEC.
This was discovered on 32-bit ARM platform when extending the max deferment value.
Cc: Frederic Weisbecker fweisbec@gmail.com Signed-off-by: Kevin Hilman khilman@linaro.org --- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 4b1fe3e..3d7c80e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2203,7 +2203,7 @@ u64 scheduler_tick_max_deferment(void) if (time_before_eq(next, now)) return 0;
- return jiffies_to_usecs(next - now) * NSEC_PER_USEC; + return (u64)jiffies_to_usecs(next - now) * NSEC_PER_USEC; }
static __init int sched_nohz_full_init_debug(void)
Frederic,
On Mon, Sep 16, 2013 at 3:43 PM, Kevin Hilman khilman@linaro.org wrote:
Allow debugfs override of sched_tick_max_deferment in order to ease finding/fixing the remaining issues with full nohz.
The value to be written is in jiffies, and -1 means the max deferment is disabled (scheduler_tick_max_deferment() returns KTIME_MAX.)
Cc: Frederic Weisbecker fweisbec@gmail.com Signed-off-by: Kevin Hilman khilman@linaro.org
Any objections to this series for ease of debugging and tracking down issues with the residual tick?
Kevin
kernel/sched/core.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5ac63c9..4b1fe3e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2175,6 +2175,8 @@ void scheduler_tick(void) }
#ifdef CONFIG_NO_HZ_FULL +static u32 sched_tick_max_deferment = HZ;
/**
- scheduler_tick_max_deferment
@@ -2193,13 +2195,25 @@ u64 scheduler_tick_max_deferment(void) struct rq *rq = this_rq(); unsigned long next, now = ACCESS_ONCE(jiffies);
next = rq->last_sched_tick + HZ;
if (sched_tick_max_deferment == -1)return KTIME_MAX;next = rq->last_sched_tick + sched_tick_max_deferment; if (time_before_eq(next, now)) return 0; return jiffies_to_usecs(next - now) * NSEC_PER_USEC;}
+static __init int sched_nohz_full_init_debug(void) +{
debugfs_create_u32("sched_tick_max_deferment", 0644, NULL,&sched_tick_max_deferment);return 0;+} +late_initcall(sched_nohz_full_init_debug); #endif
notrace unsigned long get_parent_ip(unsigned long addr)
1.8.3
linaro-kernel@lists.linaro.org
-
Kevin Hilman