* Re: [RFC][PATCH] cache __next_timer_interrupt result
2009-07-21 18:25 [RFC][PATCH] cache __next_timer_interrupt result Martin Schwidefsky
@ 2009-07-22 14:38 ` Thomas Gleixner
2009-07-22 16:02 ` Martin Schwidefsky
2009-08-04 14:16 ` [tip:timers/core] timers: Cache " tip-bot for Martin Schwidefsky
2009-08-04 18:30 ` tip-bot for Martin Schwidefsky
2 siblings, 1 reply; 6+ messages in thread
From: Thomas Gleixner @ 2009-07-22 14:38 UTC (permalink / raw)
To: Martin Schwidefsky
Cc: linux-kernel, Ingo Molnar, john stultz, Venki Pallipadi
On Tue, 21 Jul 2009, Martin Schwidefsky wrote:
> From: Martin Schwidefsky <schwidefsky@de.ibm.com>
>
> Each time a cpu goes to sleep on a NOHZ=y system the timer wheel is
> searched for the next timer interrupt. It can take quite a few cycles
> to find the next pending timer. This patch adds a field to tvec_base
> that caches the result of __next_timer_interrupt. The hit ratio is
> around 80% on my thinkpad under normal use, on a server I've seen
Nice, I like it.
> hit ratios from 5% to 95% dependent on the workload.
Which workloads result in lower hit ratios ? Heavy networking ?
Thanks,
tglx
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC][PATCH] cache __next_timer_interrupt result
2009-07-22 14:38 ` Thomas Gleixner
@ 2009-07-22 16:02 ` Martin Schwidefsky
0 siblings, 0 replies; 6+ messages in thread
From: Martin Schwidefsky @ 2009-07-22 16:02 UTC (permalink / raw)
To: Thomas Gleixner; +Cc: linux-kernel, Ingo Molnar, john stultz, Venki Pallipadi
On Wed, 22 Jul 2009 16:38:18 +0200 (CEST)
Thomas Gleixner <tglx@linutronix.de> wrote:
> On Tue, 21 Jul 2009, Martin Schwidefsky wrote:
>
> > From: Martin Schwidefsky <schwidefsky@de.ibm.com>
> >
> > Each time a cpu goes to sleep on a NOHZ=y system the timer wheel is
> > searched for the next timer interrupt. It can take quite a few cycles
> > to find the next pending timer. This patch adds a field to tvec_base
> > that caches the result of __next_timer_interrupt. The hit ratio is
> > around 80% on my thinkpad under normal use, on a server I've seen
>
> Nice, I like it.
Thanks :-)
> > hit ratios from 5% to 95% dependent on the workload.
>
> Which workloads result in lower hit ratios ? Heavy networking ?
5% ping-pong packet over loopback between two cpus. So yes, networking.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [tip:timers/core] timers: Cache __next_timer_interrupt result
2009-07-21 18:25 [RFC][PATCH] cache __next_timer_interrupt result Martin Schwidefsky
2009-07-22 14:38 ` Thomas Gleixner
@ 2009-08-04 14:16 ` tip-bot for Martin Schwidefsky
2009-08-04 17:47 ` Martin Schwidefsky
2009-08-04 18:30 ` tip-bot for Martin Schwidefsky
2 siblings, 1 reply; 6+ messages in thread
From: tip-bot for Martin Schwidefsky @ 2009-08-04 14:16 UTC (permalink / raw)
To: linux-tip-commits
Cc: linux-kernel, hpa, mingo, johnstul, venkatesh.pallipadi,
schwidefsky, tglx, mingo
Commit-ID: 91ff44bdb806a3d26436cc4f5e4816d1ea75b34b
Gitweb: http://git.kernel.org/tip/91ff44bdb806a3d26436cc4f5e4816d1ea75b34b
Author: Martin Schwidefsky <schwidefsky@de.ibm.com>
AuthorDate: Tue, 21 Jul 2009 20:25:05 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 4 Aug 2009 16:07:51 +0200
timers: Cache __next_timer_interrupt result
Each time a cpu goes to sleep on a NOHZ=y system the timer
wheel is searched for the next timer interrupt. It can take
quite a few cycles to find the next pending timer.
This patch adds a field to tvec_base that caches the result of
__next_timer_interrupt.
The hit ratio is around 80% on my thinkpad under normal use, on
a server I've seen hit ratios from 5% to 95% dependent on the
workload.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Venki Pallipadi <venkatesh.pallipadi@intel.com>
LKML-Reference: <20090721202505.7d56a079@skybase>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/timer.c | 24 +++++++++++++++++++++++-
1 files changed, 23 insertions(+), 1 deletions(-)
diff --git a/kernel/timer.c b/kernel/timer.c
index 0b36b9e..7769923 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -72,6 +72,7 @@ struct tvec_base {
spinlock_t lock;
struct timer_list *running_timer;
unsigned long timer_jiffies;
+ unsigned long next_timer;
struct tvec_root tv1;
struct tvec tv2;
struct tvec tv3;
@@ -622,6 +623,9 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
if (timer_pending(timer)) {
detach_timer(timer, 0);
+ if (timer->expires == base->next_timer &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = base->timer_jiffies;
ret = 1;
} else {
if (pending_only)
@@ -663,6 +667,9 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
}
timer->expires = expires;
+ if (timer->expires < base->next_timer &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = timer->expires;
internal_add_timer(base, timer);
out_unlock:
@@ -781,6 +788,9 @@ void add_timer_on(struct timer_list *timer, int cpu)
spin_lock_irqsave(&base->lock, flags);
timer_set_base(timer, base);
debug_timer_activate(timer);
+ if (timer->expires < base->next_timer &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = timer->expires;
internal_add_timer(base, timer);
/*
* Check whether the other CPU is idle and needs to be
@@ -817,6 +827,9 @@ int del_timer(struct timer_list *timer)
base = lock_timer_base(timer, &flags);
if (timer_pending(timer)) {
detach_timer(timer, 1);
+ if (timer->expires == base->next_timer &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = base->timer_jiffies;
ret = 1;
}
spin_unlock_irqrestore(&base->lock, flags);
@@ -850,6 +863,9 @@ int try_to_del_timer_sync(struct timer_list *timer)
ret = 0;
if (timer_pending(timer)) {
detach_timer(timer, 1);
+ if (timer->expires == base->next_timer &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = base->timer_jiffies;
ret = 1;
}
out:
@@ -1134,7 +1150,9 @@ unsigned long get_next_timer_interrupt(unsigned long now)
unsigned long expires;
spin_lock(&base->lock);
- expires = __next_timer_interrupt(base);
+ if (base->next_timer <= base->timer_jiffies)
+ base->next_timer = __next_timer_interrupt(base);
+ expires = base->next_timer;
spin_unlock(&base->lock);
if (time_before_eq(expires, now))
@@ -1523,6 +1541,7 @@ static int __cpuinit init_timers_cpu(int cpu)
INIT_LIST_HEAD(base->tv1.vec + j);
base->timer_jiffies = jiffies;
+ base->next_timer = base->timer_jiffies;
return 0;
}
@@ -1535,6 +1554,9 @@ static void migrate_timer_list(struct tvec_base *new_base, struct list_head *hea
timer = list_first_entry(head, struct timer_list, entry);
detach_timer(timer, 0);
timer_set_base(timer, new_base);
+ if (timer->expires < new_base->next_timer &&
+ !tbase_get_deferrable(timer->base))
+ new_base->next_timer = timer->expires;
internal_add_timer(new_base, timer);
}
}
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [tip:timers/core] timers: Cache __next_timer_interrupt result
2009-08-04 14:16 ` [tip:timers/core] timers: Cache " tip-bot for Martin Schwidefsky
@ 2009-08-04 17:47 ` Martin Schwidefsky
0 siblings, 0 replies; 6+ messages in thread
From: Martin Schwidefsky @ 2009-08-04 17:47 UTC (permalink / raw)
To: mingo, hpa, linux-kernel, johnstul, venkatesh.pallipadi, tglx,
mingo
On Tue, 4 Aug 2009 14:16:04 GMT
tip-bot for Martin Schwidefsky <schwidefsky@de.ibm.com> wrote:
> Commit-ID: 91ff44bdb806a3d26436cc4f5e4816d1ea75b34b
> Gitweb: http://git.kernel.org/tip/91ff44bdb806a3d26436cc4f5e4816d1ea75b34b
> Author: Martin Schwidefsky <schwidefsky@de.ibm.com>
> AuthorDate: Tue, 21 Jul 2009 20:25:05 +0200
> Committer: Ingo Molnar <mingo@elte.hu>
> CommitDate: Tue, 4 Aug 2009 16:07:51 +0200
>
> timers: Cache __next_timer_interrupt result
Seeing that patch again after a few days and all of a sudden I find the
bugs .. I really should use time_before and time_before_eq instead of
comparing the expires values directly. New patch:
--
Subject: [PATCH] cache __next_timer_interrupt result
From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Each time a cpu goes to sleep on a NOHZ=y system the timer wheel is
searched for the next timer interrupt. It can take quite a few cycles
to find the next pending timer. This patch adds a field to tvec_base
that caches the result of __next_timer_interrupt. The hit ratio is
around 80% on my thinkpad under normal use, on a server I've seen
hit ratios from 5% to 95% dependent on the workload.
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Venki Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
kernel/timer.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff -urpN linux-2.6/kernel/timer.c linux-2.6-patched/kernel/timer.c
--- linux-2.6/kernel/timer.c 2009-08-04 19:45:03.000000000 +0200
+++ linux-2.6-patched/kernel/timer.c 2009-08-04 19:45:19.000000000 +0200
@@ -72,6 +72,7 @@ struct tvec_base {
spinlock_t lock;
struct timer_list *running_timer;
unsigned long timer_jiffies;
+ unsigned long next_timer;
struct tvec_root tv1;
struct tvec tv2;
struct tvec tv3;
@@ -622,6 +623,9 @@ __mod_timer(struct timer_list *timer, un
if (timer_pending(timer)) {
detach_timer(timer, 0);
+ if (timer->expires == base->next_timer &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = base->timer_jiffies;
ret = 1;
} else {
if (pending_only)
@@ -663,6 +667,9 @@ __mod_timer(struct timer_list *timer, un
}
timer->expires = expires;
+ if (time_before(timer->expires, base->next_timer) &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = timer->expires;
internal_add_timer(base, timer);
out_unlock:
@@ -781,6 +788,9 @@ void add_timer_on(struct timer_list *tim
spin_lock_irqsave(&base->lock, flags);
timer_set_base(timer, base);
debug_timer_activate(timer);
+ if (time_before(timer->expires, base->next_timer) &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = timer->expires;
internal_add_timer(base, timer);
/*
* Check whether the other CPU is idle and needs to be
@@ -817,6 +827,9 @@ int del_timer(struct timer_list *timer)
base = lock_timer_base(timer, &flags);
if (timer_pending(timer)) {
detach_timer(timer, 1);
+ if (timer->expires == base->next_timer &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = base->timer_jiffies;
ret = 1;
}
spin_unlock_irqrestore(&base->lock, flags);
@@ -850,6 +863,9 @@ int try_to_del_timer_sync(struct timer_l
ret = 0;
if (timer_pending(timer)) {
detach_timer(timer, 1);
+ if (timer->expires == base->next_timer &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = base->timer_jiffies;
ret = 1;
}
out:
@@ -1134,7 +1150,9 @@ unsigned long get_next_timer_interrupt(u
unsigned long expires;
spin_lock(&base->lock);
- expires = __next_timer_interrupt(base);
+ if (time_before_eq(base->next_timer, base->timer_jiffies))
+ base->next_timer = __next_timer_interrupt(base);
+ expires = base->next_timer;
spin_unlock(&base->lock);
if (time_before_eq(expires, now))
@@ -1523,6 +1541,7 @@ static int __cpuinit init_timers_cpu(int
INIT_LIST_HEAD(base->tv1.vec + j);
base->timer_jiffies = jiffies;
+ base->next_timer = base->timer_jiffies;
return 0;
}
@@ -1535,6 +1554,9 @@ static void migrate_timer_list(struct tv
timer = list_first_entry(head, struct timer_list, entry);
detach_timer(timer, 0);
timer_set_base(timer, new_base);
+ if (time_before(timer->expires, new_base->next_timer) &&
+ !tbase_get_deferrable(timer->base))
+ new_base->next_timer = timer->expires;
internal_add_timer(new_base, timer);
}
}
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [tip:timers/core] timers: Cache __next_timer_interrupt result
2009-07-21 18:25 [RFC][PATCH] cache __next_timer_interrupt result Martin Schwidefsky
2009-07-22 14:38 ` Thomas Gleixner
2009-08-04 14:16 ` [tip:timers/core] timers: Cache " tip-bot for Martin Schwidefsky
@ 2009-08-04 18:30 ` tip-bot for Martin Schwidefsky
2 siblings, 0 replies; 6+ messages in thread
From: tip-bot for Martin Schwidefsky @ 2009-08-04 18:30 UTC (permalink / raw)
To: linux-tip-commits
Cc: linux-kernel, hpa, mingo, johnstul, venkatesh.pallipadi,
schwidefsky, tglx, mingo
Commit-ID: 97fd9ed48ce2b807edc363bef3e817aeeb5cd5e6
Gitweb: http://git.kernel.org/tip/97fd9ed48ce2b807edc363bef3e817aeeb5cd5e6
Author: Martin Schwidefsky <schwidefsky@de.ibm.com>
AuthorDate: Tue, 21 Jul 2009 20:25:05 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 4 Aug 2009 20:28:25 +0200
timers: Cache __next_timer_interrupt result
Each time a cpu goes to sleep on a NOHZ=y system the timer
wheel is searched for the next timer interrupt. It can take
quite a few cycles to find the next pending timer.
This patch adds a field to tvec_base that caches the result of
__next_timer_interrupt.
The hit ratio is around 80% on my thinkpad under normal use, on
a server I've seen hit ratios from 5% to 95% dependent on the
workload.
-v2: jiffies wrap fixes
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Venki Pallipadi <venkatesh.pallipadi@intel.com>
LKML-Reference: <20090721202505.7d56a079@skybase>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/timer.c | 24 +++++++++++++++++++++++-
1 files changed, 23 insertions(+), 1 deletions(-)
diff --git a/kernel/timer.c b/kernel/timer.c
index 0b36b9e..5c1e49e 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -72,6 +72,7 @@ struct tvec_base {
spinlock_t lock;
struct timer_list *running_timer;
unsigned long timer_jiffies;
+ unsigned long next_timer;
struct tvec_root tv1;
struct tvec tv2;
struct tvec tv3;
@@ -622,6 +623,9 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
if (timer_pending(timer)) {
detach_timer(timer, 0);
+ if (timer->expires == base->next_timer &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = base->timer_jiffies;
ret = 1;
} else {
if (pending_only)
@@ -663,6 +667,9 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
}
timer->expires = expires;
+ if (time_before(timer->expires, base->next_timer) &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = timer->expires;
internal_add_timer(base, timer);
out_unlock:
@@ -781,6 +788,9 @@ void add_timer_on(struct timer_list *timer, int cpu)
spin_lock_irqsave(&base->lock, flags);
timer_set_base(timer, base);
debug_timer_activate(timer);
+ if (time_before(timer->expires, base->next_timer) &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = timer->expires;
internal_add_timer(base, timer);
/*
* Check whether the other CPU is idle and needs to be
@@ -817,6 +827,9 @@ int del_timer(struct timer_list *timer)
base = lock_timer_base(timer, &flags);
if (timer_pending(timer)) {
detach_timer(timer, 1);
+ if (timer->expires == base->next_timer &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = base->timer_jiffies;
ret = 1;
}
spin_unlock_irqrestore(&base->lock, flags);
@@ -850,6 +863,9 @@ int try_to_del_timer_sync(struct timer_list *timer)
ret = 0;
if (timer_pending(timer)) {
detach_timer(timer, 1);
+ if (timer->expires == base->next_timer &&
+ !tbase_get_deferrable(timer->base))
+ base->next_timer = base->timer_jiffies;
ret = 1;
}
out:
@@ -1134,7 +1150,9 @@ unsigned long get_next_timer_interrupt(unsigned long now)
unsigned long expires;
spin_lock(&base->lock);
- expires = __next_timer_interrupt(base);
+ if (time_before_eq(base->next_timer, base->timer_jiffies))
+ base->next_timer = __next_timer_interrupt(base);
+ expires = base->next_timer;
spin_unlock(&base->lock);
if (time_before_eq(expires, now))
@@ -1523,6 +1541,7 @@ static int __cpuinit init_timers_cpu(int cpu)
INIT_LIST_HEAD(base->tv1.vec + j);
base->timer_jiffies = jiffies;
+ base->next_timer = base->timer_jiffies;
return 0;
}
@@ -1535,6 +1554,9 @@ static void migrate_timer_list(struct tvec_base *new_base, struct list_head *hea
timer = list_first_entry(head, struct timer_list, entry);
detach_timer(timer, 0);
timer_set_base(timer, new_base);
+ if (time_before(timer->expires, new_base->next_timer) &&
+ !tbase_get_deferrable(timer->base))
+ new_base->next_timer = timer->expires;
internal_add_timer(new_base, timer);
}
}
^ permalink raw reply related [flat|nested] 6+ messages in thread