From e075867681ca9b8c0b8823e24d0fb4ce3b4f2655 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <fweisbec@gmail.com>
Date: Fri, 10 Oct 2014 02:44:01 +0200
Subject: jiffies: Remove HZ > USEC_PER_SEC special case

HZ never goes much further 1000 and a bit. And if we ever reach one tick
per microsecond, we might be having a problem.

Lets stop maintaining this special case, just leave a paranoid check.

Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc; John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 include/linux/jiffies.h | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

(limited to 'include/linux')

diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
index 535fd3bb1ba8..7c6febede6ba 100644
--- a/include/linux/jiffies.h
+++ b/include/linux/jiffies.h
@@ -363,18 +363,11 @@ static inline unsigned long msecs_to_jiffies(const unsigned int m)
 }
 
 extern unsigned long __usecs_to_jiffies(const unsigned int u);
-#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
+#if !(USEC_PER_SEC % HZ)
 static inline unsigned long _usecs_to_jiffies(const unsigned int u)
 {
 	return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
 }
-#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
-static inline unsigned long _usecs_to_jiffies(const unsigned int u)
-{
-	return u * (HZ / USEC_PER_SEC);
-}
-static inline unsigned long _usecs_to_jiffies(const unsigned int u)
-{
 #else
 static inline unsigned long _usecs_to_jiffies(const unsigned int u)
 {
-- 
cgit v1.2.3


From 03f6199a359e460714b6bd08c10b566760f150a6 Mon Sep 17 00:00:00 2001
From: Chris Metcalf <cmetcalf@ezchip.com>
Date: Fri, 10 Jul 2015 15:37:25 -0400
Subject: nohz: Prevent tilegx network driver interrupts

Normally the tilegx networking shim sends irqs to all the cores
to distribute the load of processing incoming-packet interrupts,
so that you can get to multiple Gb's of traffic inbound.

However, in nohz_full mode we don't want to interrupt the
nohz_full cores by default, so we limit the set of cores we use
to only the online housekeeping cores.

To make client code easier to read, we introduce a new nohz_full
accessor, housekeeping_cpumask(), which returns a pointer to the
housekeeping_mask if nohz_full is enabled, and otherwise returns
the cpu_possible_mask.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 drivers/net/ethernet/tile/tilegx.c | 4 +++-
 include/linux/tick.h               | 9 +++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

(limited to 'include/linux')

diff --git a/drivers/net/ethernet/tile/tilegx.c b/drivers/net/ethernet/tile/tilegx.c
index a3f7610002aa..0a15acc075b3 100644
--- a/drivers/net/ethernet/tile/tilegx.c
+++ b/drivers/net/ethernet/tile/tilegx.c
@@ -40,6 +40,7 @@
 #include <linux/tcp.h>
 #include <linux/net_tstamp.h>
 #include <linux/ptp_clock_kernel.h>
+#include <linux/tick.h>
 
 #include <asm/checksum.h>
 #include <asm/homecache.h>
@@ -2273,7 +2274,8 @@ static int __init tile_net_init_module(void)
 		tile_net_dev_init(name, mac);
 
 	if (!network_cpus_init())
-		network_cpus_map = *cpu_online_mask;
+		cpumask_and(&network_cpus_map, housekeeping_cpumask(),
+			    cpu_online_mask);
 
 	return 0;
 }
diff --git a/include/linux/tick.h b/include/linux/tick.h
index edbfc9a5293e..1ca93f2de6f5 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -163,6 +163,15 @@ static inline void tick_nohz_full_kick_all(void) { }
 static inline void __tick_nohz_task_switch(struct task_struct *tsk) { }
 #endif
 
+static inline const struct cpumask *housekeeping_cpumask(void)
+{
+#ifdef CONFIG_NO_HZ_FULL
+	if (tick_nohz_full_enabled())
+		return housekeeping_mask;
+#endif
+	return cpu_possible_mask;
+}
+
 static inline bool is_housekeeping_cpu(int cpu)
 {
 #ifdef CONFIG_NO_HZ_FULL
-- 
cgit v1.2.3


From 73738a95d00467812664b7f86ba3052f5faf96d7 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <fweisbec@gmail.com>
Date: Wed, 27 May 2015 19:22:08 +0200
Subject: nohz: Restart nohz full tick from irq exit

Restart the tick when necessary from the irq exit path. It makes nohz
full more flexible, simplify the related IPIs and doesn't bring
significant overhead on irq exit.

In a longer term view, it will allow us to piggyback the nohz kick
on the scheduler IPI in the future instead of sending a dedicated IPI
that often doubles the scheduler IPI on task wakeup. This will require
more changes though including careful review of resched_curr() callers
to include nohz full needs.

Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 include/linux/tick.h     |  8 --------
 kernel/time/tick-sched.c | 34 ++++++++++------------------------
 2 files changed, 10 insertions(+), 32 deletions(-)

(limited to 'include/linux')

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 1ca93f2de6f5..7d35b0fec399 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -147,7 +147,6 @@ static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask)
 		cpumask_or(mask, mask, tick_nohz_full_mask);
 }
 
-extern void __tick_nohz_full_check(void);
 extern void tick_nohz_full_kick(void);
 extern void tick_nohz_full_kick_cpu(int cpu);
 extern void tick_nohz_full_kick_all(void);
@@ -156,7 +155,6 @@ extern void __tick_nohz_task_switch(struct task_struct *tsk);
 static inline bool tick_nohz_full_enabled(void) { return false; }
 static inline bool tick_nohz_full_cpu(int cpu) { return false; }
 static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { }
-static inline void __tick_nohz_full_check(void) { }
 static inline void tick_nohz_full_kick_cpu(int cpu) { }
 static inline void tick_nohz_full_kick(void) { }
 static inline void tick_nohz_full_kick_all(void) { }
@@ -190,12 +188,6 @@ static inline void housekeeping_affine(struct task_struct *t)
 #endif
 }
 
-static inline void tick_nohz_full_check(void)
-{
-	if (tick_nohz_full_enabled())
-		__tick_nohz_full_check();
-}
-
 static inline void tick_nohz_task_switch(struct task_struct *tsk)
 {
 	if (tick_nohz_full_enabled())
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index d6c8eff6e7b4..a06cd4af0ff1 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -197,25 +197,9 @@ static bool can_stop_full_tick(void)
 	return true;
 }
 
-static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now);
-
-/*
- * Re-evaluate the need for the tick on the current CPU
- * and restart it if necessary.
- */
-void __tick_nohz_full_check(void)
-{
-	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
-
-	if (tick_nohz_full_cpu(smp_processor_id())) {
-		if (ts->tick_stopped && !can_stop_full_tick())
-			tick_nohz_restart_sched_tick(ts, ktime_get());
-	}
-}
-
 static void nohz_full_kick_work_func(struct irq_work *work)
 {
-	__tick_nohz_full_check();
+	/* Empty, the tick restart happens on tick_nohz_irq_exit() */
 }
 
 static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
@@ -250,7 +234,7 @@ void tick_nohz_full_kick_cpu(int cpu)
 
 static void nohz_full_kick_ipi(void *info)
 {
-	__tick_nohz_full_check();
+	/* Empty, the tick restart happens on tick_nohz_irq_exit() */
 }
 
 /*
@@ -703,7 +687,9 @@ out:
 	return tick;
 }
 
-static void tick_nohz_full_stop_tick(struct tick_sched *ts)
+static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now);
+
+static void tick_nohz_full_update_tick(struct tick_sched *ts)
 {
 #ifdef CONFIG_NO_HZ_FULL
 	int cpu = smp_processor_id();
@@ -714,10 +700,10 @@ static void tick_nohz_full_stop_tick(struct tick_sched *ts)
 	if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
 		return;
 
-	if (!can_stop_full_tick())
-		return;
-
-	tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
+	if (can_stop_full_tick())
+		tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
+	else if (ts->tick_stopped)
+		tick_nohz_restart_sched_tick(ts, ktime_get());
 #endif
 }
 
@@ -847,7 +833,7 @@ void tick_nohz_irq_exit(void)
 	if (ts->inidle)
 		__tick_nohz_idle_enter(ts);
 	else
-		tick_nohz_full_stop_tick(ts);
+		tick_nohz_full_update_tick(ts);
 }
 
 /**
-- 
cgit v1.2.3


From de734f89b67c2df30e35a09e7e56a3659e5b6ac6 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <fweisbec@gmail.com>
Date: Thu, 11 Jun 2015 18:07:12 +0200
Subject: nohz: Remove useless argument on tick_nohz_task_switch()

Leftover from early code.

Cc: Christoph Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 include/linux/tick.h     | 8 ++++----
 kernel/sched/core.c      | 2 +-
 kernel/time/tick-sched.c | 2 +-
 3 files changed, 6 insertions(+), 6 deletions(-)

(limited to 'include/linux')

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 7d35b0fec399..48d901f83f92 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -150,7 +150,7 @@ static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask)
 extern void tick_nohz_full_kick(void);
 extern void tick_nohz_full_kick_cpu(int cpu);
 extern void tick_nohz_full_kick_all(void);
-extern void __tick_nohz_task_switch(struct task_struct *tsk);
+extern void __tick_nohz_task_switch(void);
 #else
 static inline bool tick_nohz_full_enabled(void) { return false; }
 static inline bool tick_nohz_full_cpu(int cpu) { return false; }
@@ -158,7 +158,7 @@ static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { }
 static inline void tick_nohz_full_kick_cpu(int cpu) { }
 static inline void tick_nohz_full_kick(void) { }
 static inline void tick_nohz_full_kick_all(void) { }
-static inline void __tick_nohz_task_switch(struct task_struct *tsk) { }
+static inline void __tick_nohz_task_switch(void) { }
 #endif
 
 static inline const struct cpumask *housekeeping_cpumask(void)
@@ -188,10 +188,10 @@ static inline void housekeeping_affine(struct task_struct *t)
 #endif
 }
 
-static inline void tick_nohz_task_switch(struct task_struct *tsk)
+static inline void tick_nohz_task_switch(void)
 {
 	if (tick_nohz_full_enabled())
-		__tick_nohz_task_switch(tsk);
+		__tick_nohz_task_switch();
 }
 
 #endif
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 78b4bad10081..4d34035bb3ee 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2489,7 +2489,7 @@ static struct rq *finish_task_switch(struct task_struct *prev)
 		put_task_struct(prev);
 	}
 
-	tick_nohz_task_switch(current);
+	tick_nohz_task_switch();
 	return rq;
 }
 
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 6b0d14d4c350..3319e16f31e5 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -258,7 +258,7 @@ void tick_nohz_full_kick_all(void)
  * It might need the tick due to per task/process properties:
  * perf events, posix cpu timers, ...
  */
-void __tick_nohz_task_switch(struct task_struct *tsk)
+void __tick_nohz_task_switch(void)
 {
 	unsigned long flags;
 
-- 
cgit v1.2.3