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authorIngo Molnar <mingo@kernel.org>2013-08-14 17:58:56 +0200
committerIngo Molnar <mingo@kernel.org>2013-08-14 17:58:56 +0200
commit6f1d657668ac3041b65265d3653d7e9172a0d603 (patch)
tree6e837c683783708637cc4caf9de759166c7469b7 /kernel/time
parentd4e4ab86bcba5a72779c43dc1459f71fea3d89c8 (diff)
parentd13508f9440e46dccac6a2dd48d51a73b2207482 (diff)
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Merge branch 'timers/nohz-v3' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into timers/nohz
Pull nohz improvements from Frederic Weisbecker: " It mostly contains fixes and full dynticks off-case optimizations. I believe that distros want to enable this feature so it seems important to optimize the case where the "nohz_full=" parameter is empty. ie: I'm trying to remove any performance regression that comes with NO_HZ_FULL=y when the feature is not used. This patchset improves the current situation a lot (off-case appears to be around 11% faster with hackbench, although I guess it may vary depending on the configuration but it should be significantly faster in any case) now there is still some work to do: I can still observe a remaining loss of 1.6% throughput seen with hackbench compared to CONFIG_NO_HZ_FULL=n. " Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/Kconfig1
-rw-r--r--kernel/time/sched_clock.c2
-rw-r--r--kernel/time/tick-sched.c59
3 files changed, 28 insertions, 34 deletions
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 70f27e8..747bbc7 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -105,7 +105,6 @@ config NO_HZ_FULL
select RCU_USER_QS
select RCU_NOCB_CPU
select VIRT_CPU_ACCOUNTING_GEN
- select CONTEXT_TRACKING_FORCE
select IRQ_WORK
help
Adaptively try to shutdown the tick whenever possible, even when
diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
index a326f27..0b479a6 100644
--- a/kernel/time/sched_clock.c
+++ b/kernel/time/sched_clock.c
@@ -121,7 +121,7 @@ void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate)
BUG_ON(bits > 32);
WARN_ON(!irqs_disabled());
read_sched_clock = read;
- sched_clock_mask = (1 << bits) - 1;
+ sched_clock_mask = (1ULL << bits) - 1;
cd.rate = rate;
/* calculate the mult/shift to convert counter ticks to ns. */
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index e77edc9..adea6fc3 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -23,6 +23,7 @@
#include <linux/irq_work.h>
#include <linux/posix-timers.h>
#include <linux/perf_event.h>
+#include <linux/context_tracking.h>
#include <asm/irq_regs.h>
@@ -148,8 +149,8 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
}
#ifdef CONFIG_NO_HZ_FULL
-static cpumask_var_t nohz_full_mask;
-bool have_nohz_full_mask;
+cpumask_var_t tick_nohz_full_mask;
+bool tick_nohz_full_running;
static bool can_stop_full_tick(void)
{
@@ -182,7 +183,8 @@ static bool can_stop_full_tick(void)
* Don't allow the user to think they can get
* full NO_HZ with this machine.
*/
- WARN_ONCE(1, "NO_HZ FULL will not work with unstable sched clock");
+ WARN_ONCE(tick_nohz_full_running,
+ "NO_HZ FULL will not work with unstable sched clock");
return false;
}
#endif
@@ -196,7 +198,7 @@ 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)
+void __tick_nohz_full_check(void)
{
struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
@@ -210,7 +212,7 @@ void tick_nohz_full_check(void)
static void nohz_full_kick_work_func(struct irq_work *work)
{
- tick_nohz_full_check();
+ __tick_nohz_full_check();
}
static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
@@ -229,7 +231,7 @@ void tick_nohz_full_kick(void)
static void nohz_full_kick_ipi(void *info)
{
- tick_nohz_full_check();
+ __tick_nohz_full_check();
}
/*
@@ -238,11 +240,11 @@ static void nohz_full_kick_ipi(void *info)
*/
void tick_nohz_full_kick_all(void)
{
- if (!have_nohz_full_mask)
+ if (!tick_nohz_full_running)
return;
preempt_disable();
- smp_call_function_many(nohz_full_mask,
+ smp_call_function_many(tick_nohz_full_mask,
nohz_full_kick_ipi, NULL, false);
preempt_enable();
}
@@ -252,7 +254,7 @@ 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(struct task_struct *tsk)
{
unsigned long flags;
@@ -268,31 +270,23 @@ out:
local_irq_restore(flags);
}
-int tick_nohz_full_cpu(int cpu)
-{
- if (!have_nohz_full_mask)
- return 0;
-
- return cpumask_test_cpu(cpu, nohz_full_mask);
-}
-
/* Parse the boot-time nohz CPU list from the kernel parameters. */
static int __init tick_nohz_full_setup(char *str)
{
int cpu;
- alloc_bootmem_cpumask_var(&nohz_full_mask);
- if (cpulist_parse(str, nohz_full_mask) < 0) {
+ alloc_bootmem_cpumask_var(&tick_nohz_full_mask);
+ if (cpulist_parse(str, tick_nohz_full_mask) < 0) {
pr_warning("NOHZ: Incorrect nohz_full cpumask\n");
return 1;
}
cpu = smp_processor_id();
- if (cpumask_test_cpu(cpu, nohz_full_mask)) {
+ if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) {
pr_warning("NO_HZ: Clearing %d from nohz_full range for timekeeping\n", cpu);
- cpumask_clear_cpu(cpu, nohz_full_mask);
+ cpumask_clear_cpu(cpu, tick_nohz_full_mask);
}
- have_nohz_full_mask = true;
+ tick_nohz_full_running = true;
return 1;
}
@@ -310,7 +304,7 @@ static int tick_nohz_cpu_down_callback(struct notifier_block *nfb,
* If we handle the timekeeping duty for full dynticks CPUs,
* we can't safely shutdown that CPU.
*/
- if (have_nohz_full_mask && tick_do_timer_cpu == cpu)
+ if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
return NOTIFY_BAD;
break;
}
@@ -329,14 +323,14 @@ static int tick_nohz_init_all(void)
int err = -1;
#ifdef CONFIG_NO_HZ_FULL_ALL
- if (!alloc_cpumask_var(&nohz_full_mask, GFP_KERNEL)) {
+ if (!alloc_cpumask_var(&tick_nohz_full_mask, GFP_KERNEL)) {
pr_err("NO_HZ: Can't allocate full dynticks cpumask\n");
return err;
}
err = 0;
- cpumask_setall(nohz_full_mask);
- cpumask_clear_cpu(smp_processor_id(), nohz_full_mask);
- have_nohz_full_mask = true;
+ cpumask_setall(tick_nohz_full_mask);
+ cpumask_clear_cpu(smp_processor_id(), tick_nohz_full_mask);
+ tick_nohz_full_running = true;
#endif
return err;
}
@@ -345,17 +339,18 @@ void __init tick_nohz_init(void)
{
int cpu;
- if (!have_nohz_full_mask) {
+ if (!tick_nohz_full_running) {
if (tick_nohz_init_all() < 0)
return;
}
+ for_each_cpu(cpu, tick_nohz_full_mask)
+ context_tracking_cpu_set(cpu);
+
cpu_notifier(tick_nohz_cpu_down_callback, 0);
- cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), nohz_full_mask);
+ cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), tick_nohz_full_mask);
pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf);
}
-#else
-#define have_nohz_full_mask (0)
#endif
/*
@@ -733,7 +728,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
return false;
}
- if (have_nohz_full_mask) {
+ if (tick_nohz_full_enabled()) {
/*
* Keep the tick alive to guarantee timekeeping progression
* if there are full dynticks CPUs around