[PATCH tip/core/rcu 6/9] nohz_full: Add full-system idle states and variables
From: "Paul E. McKenney" This commit adds control variables and states for full-system idle. The system will progress through the states in numerical order when the system is fully idle (other than the timekeeping CPU), and reset down to the initial state if any non-timekeeping CPU goes non-idle. The current state is kept in full_sysidle_state. One flavor of RCU will be in charge of driving the state machine, defined by rcu_sysidle_state. This should be the busiest flavor of RCU. Signed-off-by: Paul E. McKenney Cc: Frederic Weisbecker Cc: Steven Rostedt Reviewed-by: Josh Triplett --- kernel/rcutree_plugin.h | 17 + 1 file changed, 17 insertions(+) diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index eab81da..a7419ce 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2378,6 +2378,23 @@ static void rcu_kick_nohz_cpu(int cpu) #ifdef CONFIG_NO_HZ_FULL_SYSIDLE /* + * Define RCU flavor that holds sysidle state. This needs to be the + * most active flavor of RCU. + */ +#ifdef CONFIG_PREEMPT_RCU +static struct rcu_state __maybe_unused *rcu_sysidle_state = _preempt_state; +#else /* #ifdef CONFIG_PREEMPT_RCU */ +static struct rcu_state __maybe_unused *rcu_sysidle_state = _sched_state; +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ + +static int __maybe_unused full_sysidle_state; /* Current system-idle state. */ +#define RCU_SYSIDLE_NOT0 /* Some CPU is not idle. */ +#define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ + +/* * Invoked to note exit from irq or task transition to idle. Note that * usermode execution does -not- count as idle here! After all, we want * to detect full-system idle states, not RCU quiescent states and grace -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH tip/core/rcu 6/9] nohz_full: Add full-system idle states and variables
From: Paul E. McKenney paul...@linux.vnet.ibm.com This commit adds control variables and states for full-system idle. The system will progress through the states in numerical order when the system is fully idle (other than the timekeeping CPU), and reset down to the initial state if any non-timekeeping CPU goes non-idle. The current state is kept in full_sysidle_state. One flavor of RCU will be in charge of driving the state machine, defined by rcu_sysidle_state. This should be the busiest flavor of RCU. Signed-off-by: Paul E. McKenney paul...@linux.vnet.ibm.com Cc: Frederic Weisbecker fweis...@gmail.com Cc: Steven Rostedt rost...@goodmis.org Reviewed-by: Josh Triplett j...@joshtriplett.org --- kernel/rcutree_plugin.h | 17 + 1 file changed, 17 insertions(+) diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index eab81da..a7419ce 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2378,6 +2378,23 @@ static void rcu_kick_nohz_cpu(int cpu) #ifdef CONFIG_NO_HZ_FULL_SYSIDLE /* + * Define RCU flavor that holds sysidle state. This needs to be the + * most active flavor of RCU. + */ +#ifdef CONFIG_PREEMPT_RCU +static struct rcu_state __maybe_unused *rcu_sysidle_state = rcu_preempt_state; +#else /* #ifdef CONFIG_PREEMPT_RCU */ +static struct rcu_state __maybe_unused *rcu_sysidle_state = rcu_sched_state; +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ + +static int __maybe_unused full_sysidle_state; /* Current system-idle state. */ +#define RCU_SYSIDLE_NOT0 /* Some CPU is not idle. */ +#define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ + +/* * Invoked to note exit from irq or task transition to idle. Note that * usermode execution does -not- count as idle here! After all, we want * to detect full-system idle states, not RCU quiescent states and grace -- 1.8.1.5 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH tip/core/rcu 6/9] nohz_full: Add full-system idle states and variables
On Sun, Aug 18, 2013 at 07:49:14PM -0700, Josh Triplett wrote: > On Sun, Aug 18, 2013 at 06:39:25PM -0700, Paul E. McKenney wrote: > > On Sat, Aug 17, 2013 at 08:09:21PM -0700, Josh Triplett wrote: > > > On Sat, Aug 17, 2013 at 06:49:41PM -0700, Paul E. McKenney wrote: > > > > From: "Paul E. McKenney" > > > > > > > > This commit adds control variables and states for full-system idle. > > > > The system will progress through the states in numerical order when > > > > the system is fully idle (other than the timekeeping CPU), and reset > > > > down to the initial state if any non-timekeeping CPU goes non-idle. > > > > The current state is kept in full_sysidle_state. > > > > > > > > A RCU_SYSIDLE_SMALL macro is defined, and systems with this number > > > > of CPUs or fewer move through the states more aggressively. The idea > > > > is that the resulting memory contention is less of a problem on small > > > > systems. Architectures can adjust this value (which defaults to 8) > > > > using CONFIG_ARCH_RCU_SYSIDLE_SMALL. > > > > > > > > One flavor of RCU will be in charge of driving the state machine, > > > > defined by rcu_sysidle_state. This should be the busiest flavor of RCU. > > > > > > > > Signed-off-by: Paul E. McKenney > > > > Cc: Frederic Weisbecker > > > > Cc: Steven Rostedt > > > > > > One issue (and one question) below; with the issue addressed, > > > Reviewed-by: Josh Triplett > > > > > > > kernel/rcutree_plugin.h | 28 > > > > 1 file changed, 28 insertions(+) > > > > > > > > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > > > > index eab81da..64a05b9f 100644 > > > > --- a/kernel/rcutree_plugin.h > > > > +++ b/kernel/rcutree_plugin.h > > > > @@ -2378,6 +2378,34 @@ static void rcu_kick_nohz_cpu(int cpu) > > > > #ifdef CONFIG_NO_HZ_FULL_SYSIDLE > > > > > > > > /* > > > > + * Handle small systems specially, accelerating their transition into > > > > + * full idle state. Allow arches to override this code's idea of > > > > + * what constitutes a "small" system. > > > > + */ > > > > +#ifdef CONFIG_ARCH_RCU_SYSIDLE_SMALL > > > > > > I don't see any Kconfig creating this new config option. > > > > > > Also, why not simply define this config option unconditionally, with a > > > default of 8, and then use its value directly? > > > > Good point, removing this and adding a Kconfig option in the > > "nohz_full: Add full-system-idle state machine" commit, with a > > default value of 8. Architecture maintainers who want something > > different can then set that up in their defconfig files. > > Sounds good. > > > > > +static int __maybe_unused full_sysidle_state; /* Current system-idle > > > > state. */ > > > > +#define RCU_SYSIDLE_NOT0 /* Some CPU is not > > > > idle. */ > > > > +#define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief > > > > period. */ > > > > +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long > > > > enough. */ > > > > +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for > > > > sysidle. */ > > > > +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle > > > > state. */ > > > > > > Perhaps there's a kernel style rule I'm not thinking of that makes it > > > verboten, but: why not use an enum for a state variable like this? > > > > I didn't trust enum interactions with xchg and cmpxchg, so opted for "int" > > instead. That said, enum is much more portable than when I last looked > > at it. Admittedly, the last time I looked at it was in the early 1980s... > > That would make sense if this was an atomic_t, but it's an int; unless I > missed something, you don't currently use xchg or cmpxchg on it. The xchg and cmpxchg show up in the "Add full-system-idle state machine" commit. Of course, now I am trying to remember why I used int instead of atomic_t in this case... :-/ Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH tip/core/rcu 6/9] nohz_full: Add full-system idle states and variables
On Sun, Aug 18, 2013 at 06:39:25PM -0700, Paul E. McKenney wrote: > On Sat, Aug 17, 2013 at 08:09:21PM -0700, Josh Triplett wrote: > > On Sat, Aug 17, 2013 at 06:49:41PM -0700, Paul E. McKenney wrote: > > > From: "Paul E. McKenney" > > > > > > This commit adds control variables and states for full-system idle. > > > The system will progress through the states in numerical order when > > > the system is fully idle (other than the timekeeping CPU), and reset > > > down to the initial state if any non-timekeeping CPU goes non-idle. > > > The current state is kept in full_sysidle_state. > > > > > > A RCU_SYSIDLE_SMALL macro is defined, and systems with this number > > > of CPUs or fewer move through the states more aggressively. The idea > > > is that the resulting memory contention is less of a problem on small > > > systems. Architectures can adjust this value (which defaults to 8) > > > using CONFIG_ARCH_RCU_SYSIDLE_SMALL. > > > > > > One flavor of RCU will be in charge of driving the state machine, > > > defined by rcu_sysidle_state. This should be the busiest flavor of RCU. > > > > > > Signed-off-by: Paul E. McKenney > > > Cc: Frederic Weisbecker > > > Cc: Steven Rostedt > > > > One issue (and one question) below; with the issue addressed, > > Reviewed-by: Josh Triplett > > > > > kernel/rcutree_plugin.h | 28 > > > 1 file changed, 28 insertions(+) > > > > > > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > > > index eab81da..64a05b9f 100644 > > > --- a/kernel/rcutree_plugin.h > > > +++ b/kernel/rcutree_plugin.h > > > @@ -2378,6 +2378,34 @@ static void rcu_kick_nohz_cpu(int cpu) > > > #ifdef CONFIG_NO_HZ_FULL_SYSIDLE > > > > > > /* > > > + * Handle small systems specially, accelerating their transition into > > > + * full idle state. Allow arches to override this code's idea of > > > + * what constitutes a "small" system. > > > + */ > > > +#ifdef CONFIG_ARCH_RCU_SYSIDLE_SMALL > > > > I don't see any Kconfig creating this new config option. > > > > Also, why not simply define this config option unconditionally, with a > > default of 8, and then use its value directly? > > Good point, removing this and adding a Kconfig option in the > "nohz_full: Add full-system-idle state machine" commit, with a > default value of 8. Architecture maintainers who want something > different can then set that up in their defconfig files. Sounds good. > > > +static int __maybe_unused full_sysidle_state; /* Current system-idle > > > state. */ > > > +#define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */ > > > +#define RCU_SYSIDLE_SHORT1 /* All CPUs idle for brief > > > period. */ > > > +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ > > > +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ > > > +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle > > > state. */ > > > > Perhaps there's a kernel style rule I'm not thinking of that makes it > > verboten, but: why not use an enum for a state variable like this? > > I didn't trust enum interactions with xchg and cmpxchg, so opted for "int" > instead. That said, enum is much more portable than when I last looked > at it. Admittedly, the last time I looked at it was in the early 1980s... That would make sense if this was an atomic_t, but it's an int; unless I missed something, you don't currently use xchg or cmpxchg on it. - Josh Triplett -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH tip/core/rcu 6/9] nohz_full: Add full-system idle states and variables
On Sat, Aug 17, 2013 at 08:09:21PM -0700, Josh Triplett wrote: > On Sat, Aug 17, 2013 at 06:49:41PM -0700, Paul E. McKenney wrote: > > From: "Paul E. McKenney" > > > > This commit adds control variables and states for full-system idle. > > The system will progress through the states in numerical order when > > the system is fully idle (other than the timekeeping CPU), and reset > > down to the initial state if any non-timekeeping CPU goes non-idle. > > The current state is kept in full_sysidle_state. > > > > A RCU_SYSIDLE_SMALL macro is defined, and systems with this number > > of CPUs or fewer move through the states more aggressively. The idea > > is that the resulting memory contention is less of a problem on small > > systems. Architectures can adjust this value (which defaults to 8) > > using CONFIG_ARCH_RCU_SYSIDLE_SMALL. > > > > One flavor of RCU will be in charge of driving the state machine, > > defined by rcu_sysidle_state. This should be the busiest flavor of RCU. > > > > Signed-off-by: Paul E. McKenney > > Cc: Frederic Weisbecker > > Cc: Steven Rostedt > > One issue (and one question) below; with the issue addressed, > Reviewed-by: Josh Triplett > > > kernel/rcutree_plugin.h | 28 > > 1 file changed, 28 insertions(+) > > > > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > > index eab81da..64a05b9f 100644 > > --- a/kernel/rcutree_plugin.h > > +++ b/kernel/rcutree_plugin.h > > @@ -2378,6 +2378,34 @@ static void rcu_kick_nohz_cpu(int cpu) > > #ifdef CONFIG_NO_HZ_FULL_SYSIDLE > > > > /* > > + * Handle small systems specially, accelerating their transition into > > + * full idle state. Allow arches to override this code's idea of > > + * what constitutes a "small" system. > > + */ > > +#ifdef CONFIG_ARCH_RCU_SYSIDLE_SMALL > > I don't see any Kconfig creating this new config option. > > Also, why not simply define this config option unconditionally, with a > default of 8, and then use its value directly? Good point, removing this and adding a Kconfig option in the "nohz_full: Add full-system-idle state machine" commit, with a default value of 8. Architecture maintainers who want something different can then set that up in their defconfig files. > > +static int __maybe_unused full_sysidle_state; /* Current system-idle > > state. */ > > +#define RCU_SYSIDLE_NOT0 /* Some CPU is not idle. */ > > +#define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ > > +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ > > +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ > > +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle > > state. */ > > Perhaps there's a kernel style rule I'm not thinking of that makes it > verboten, but: why not use an enum for a state variable like this? I didn't trust enum interactions with xchg and cmpxchg, so opted for "int" instead. That said, enum is much more portable than when I last looked at it. Admittedly, the last time I looked at it was in the early 1980s... Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH tip/core/rcu 6/9] nohz_full: Add full-system idle states and variables
On Sat, Aug 17, 2013 at 08:09:21PM -0700, Josh Triplett wrote: On Sat, Aug 17, 2013 at 06:49:41PM -0700, Paul E. McKenney wrote: From: Paul E. McKenney paul...@linux.vnet.ibm.com This commit adds control variables and states for full-system idle. The system will progress through the states in numerical order when the system is fully idle (other than the timekeeping CPU), and reset down to the initial state if any non-timekeeping CPU goes non-idle. The current state is kept in full_sysidle_state. A RCU_SYSIDLE_SMALL macro is defined, and systems with this number of CPUs or fewer move through the states more aggressively. The idea is that the resulting memory contention is less of a problem on small systems. Architectures can adjust this value (which defaults to 8) using CONFIG_ARCH_RCU_SYSIDLE_SMALL. One flavor of RCU will be in charge of driving the state machine, defined by rcu_sysidle_state. This should be the busiest flavor of RCU. Signed-off-by: Paul E. McKenney paul...@linux.vnet.ibm.com Cc: Frederic Weisbecker fweis...@gmail.com Cc: Steven Rostedt rost...@goodmis.org One issue (and one question) below; with the issue addressed, Reviewed-by: Josh Triplett j...@joshtriplett.org kernel/rcutree_plugin.h | 28 1 file changed, 28 insertions(+) diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index eab81da..64a05b9f 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2378,6 +2378,34 @@ static void rcu_kick_nohz_cpu(int cpu) #ifdef CONFIG_NO_HZ_FULL_SYSIDLE /* + * Handle small systems specially, accelerating their transition into + * full idle state. Allow arches to override this code's idea of + * what constitutes a small system. + */ +#ifdef CONFIG_ARCH_RCU_SYSIDLE_SMALL I don't see any Kconfig creating this new config option. Also, why not simply define this config option unconditionally, with a default of 8, and then use its value directly? Good point, removing this and adding a Kconfig option in the nohz_full: Add full-system-idle state machine commit, with a default value of 8. Architecture maintainers who want something different can then set that up in their defconfig files. +static int __maybe_unused full_sysidle_state; /* Current system-idle state. */ +#define RCU_SYSIDLE_NOT0 /* Some CPU is not idle. */ +#define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ Perhaps there's a kernel style rule I'm not thinking of that makes it verboten, but: why not use an enum for a state variable like this? I didn't trust enum interactions with xchg and cmpxchg, so opted for int instead. That said, enum is much more portable than when I last looked at it. Admittedly, the last time I looked at it was in the early 1980s... Thanx, Paul -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH tip/core/rcu 6/9] nohz_full: Add full-system idle states and variables
On Sun, Aug 18, 2013 at 06:39:25PM -0700, Paul E. McKenney wrote: On Sat, Aug 17, 2013 at 08:09:21PM -0700, Josh Triplett wrote: On Sat, Aug 17, 2013 at 06:49:41PM -0700, Paul E. McKenney wrote: From: Paul E. McKenney paul...@linux.vnet.ibm.com This commit adds control variables and states for full-system idle. The system will progress through the states in numerical order when the system is fully idle (other than the timekeeping CPU), and reset down to the initial state if any non-timekeeping CPU goes non-idle. The current state is kept in full_sysidle_state. A RCU_SYSIDLE_SMALL macro is defined, and systems with this number of CPUs or fewer move through the states more aggressively. The idea is that the resulting memory contention is less of a problem on small systems. Architectures can adjust this value (which defaults to 8) using CONFIG_ARCH_RCU_SYSIDLE_SMALL. One flavor of RCU will be in charge of driving the state machine, defined by rcu_sysidle_state. This should be the busiest flavor of RCU. Signed-off-by: Paul E. McKenney paul...@linux.vnet.ibm.com Cc: Frederic Weisbecker fweis...@gmail.com Cc: Steven Rostedt rost...@goodmis.org One issue (and one question) below; with the issue addressed, Reviewed-by: Josh Triplett j...@joshtriplett.org kernel/rcutree_plugin.h | 28 1 file changed, 28 insertions(+) diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index eab81da..64a05b9f 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2378,6 +2378,34 @@ static void rcu_kick_nohz_cpu(int cpu) #ifdef CONFIG_NO_HZ_FULL_SYSIDLE /* + * Handle small systems specially, accelerating their transition into + * full idle state. Allow arches to override this code's idea of + * what constitutes a small system. + */ +#ifdef CONFIG_ARCH_RCU_SYSIDLE_SMALL I don't see any Kconfig creating this new config option. Also, why not simply define this config option unconditionally, with a default of 8, and then use its value directly? Good point, removing this and adding a Kconfig option in the nohz_full: Add full-system-idle state machine commit, with a default value of 8. Architecture maintainers who want something different can then set that up in their defconfig files. Sounds good. +static int __maybe_unused full_sysidle_state; /* Current system-idle state. */ +#define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */ +#define RCU_SYSIDLE_SHORT1 /* All CPUs idle for brief period. */ +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ Perhaps there's a kernel style rule I'm not thinking of that makes it verboten, but: why not use an enum for a state variable like this? I didn't trust enum interactions with xchg and cmpxchg, so opted for int instead. That said, enum is much more portable than when I last looked at it. Admittedly, the last time I looked at it was in the early 1980s... That would make sense if this was an atomic_t, but it's an int; unless I missed something, you don't currently use xchg or cmpxchg on it. - Josh Triplett -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH tip/core/rcu 6/9] nohz_full: Add full-system idle states and variables
On Sun, Aug 18, 2013 at 07:49:14PM -0700, Josh Triplett wrote: On Sun, Aug 18, 2013 at 06:39:25PM -0700, Paul E. McKenney wrote: On Sat, Aug 17, 2013 at 08:09:21PM -0700, Josh Triplett wrote: On Sat, Aug 17, 2013 at 06:49:41PM -0700, Paul E. McKenney wrote: From: Paul E. McKenney paul...@linux.vnet.ibm.com This commit adds control variables and states for full-system idle. The system will progress through the states in numerical order when the system is fully idle (other than the timekeeping CPU), and reset down to the initial state if any non-timekeeping CPU goes non-idle. The current state is kept in full_sysidle_state. A RCU_SYSIDLE_SMALL macro is defined, and systems with this number of CPUs or fewer move through the states more aggressively. The idea is that the resulting memory contention is less of a problem on small systems. Architectures can adjust this value (which defaults to 8) using CONFIG_ARCH_RCU_SYSIDLE_SMALL. One flavor of RCU will be in charge of driving the state machine, defined by rcu_sysidle_state. This should be the busiest flavor of RCU. Signed-off-by: Paul E. McKenney paul...@linux.vnet.ibm.com Cc: Frederic Weisbecker fweis...@gmail.com Cc: Steven Rostedt rost...@goodmis.org One issue (and one question) below; with the issue addressed, Reviewed-by: Josh Triplett j...@joshtriplett.org kernel/rcutree_plugin.h | 28 1 file changed, 28 insertions(+) diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index eab81da..64a05b9f 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2378,6 +2378,34 @@ static void rcu_kick_nohz_cpu(int cpu) #ifdef CONFIG_NO_HZ_FULL_SYSIDLE /* + * Handle small systems specially, accelerating their transition into + * full idle state. Allow arches to override this code's idea of + * what constitutes a small system. + */ +#ifdef CONFIG_ARCH_RCU_SYSIDLE_SMALL I don't see any Kconfig creating this new config option. Also, why not simply define this config option unconditionally, with a default of 8, and then use its value directly? Good point, removing this and adding a Kconfig option in the nohz_full: Add full-system-idle state machine commit, with a default value of 8. Architecture maintainers who want something different can then set that up in their defconfig files. Sounds good. +static int __maybe_unused full_sysidle_state; /* Current system-idle state. */ +#define RCU_SYSIDLE_NOT0 /* Some CPU is not idle. */ +#define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ Perhaps there's a kernel style rule I'm not thinking of that makes it verboten, but: why not use an enum for a state variable like this? I didn't trust enum interactions with xchg and cmpxchg, so opted for int instead. That said, enum is much more portable than when I last looked at it. Admittedly, the last time I looked at it was in the early 1980s... That would make sense if this was an atomic_t, but it's an int; unless I missed something, you don't currently use xchg or cmpxchg on it. The xchg and cmpxchg show up in the Add full-system-idle state machine commit. Of course, now I am trying to remember why I used int instead of atomic_t in this case... :-/ Thanx, Paul -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH tip/core/rcu 6/9] nohz_full: Add full-system idle states and variables
On Sat, Aug 17, 2013 at 06:49:41PM -0700, Paul E. McKenney wrote: > From: "Paul E. McKenney" > > This commit adds control variables and states for full-system idle. > The system will progress through the states in numerical order when > the system is fully idle (other than the timekeeping CPU), and reset > down to the initial state if any non-timekeeping CPU goes non-idle. > The current state is kept in full_sysidle_state. > > A RCU_SYSIDLE_SMALL macro is defined, and systems with this number > of CPUs or fewer move through the states more aggressively. The idea > is that the resulting memory contention is less of a problem on small > systems. Architectures can adjust this value (which defaults to 8) > using CONFIG_ARCH_RCU_SYSIDLE_SMALL. > > One flavor of RCU will be in charge of driving the state machine, > defined by rcu_sysidle_state. This should be the busiest flavor of RCU. > > Signed-off-by: Paul E. McKenney > Cc: Frederic Weisbecker > Cc: Steven Rostedt One issue (and one question) below; with the issue addressed, Reviewed-by: Josh Triplett > kernel/rcutree_plugin.h | 28 > 1 file changed, 28 insertions(+) > > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > index eab81da..64a05b9f 100644 > --- a/kernel/rcutree_plugin.h > +++ b/kernel/rcutree_plugin.h > @@ -2378,6 +2378,34 @@ static void rcu_kick_nohz_cpu(int cpu) > #ifdef CONFIG_NO_HZ_FULL_SYSIDLE > > /* > + * Handle small systems specially, accelerating their transition into > + * full idle state. Allow arches to override this code's idea of > + * what constitutes a "small" system. > + */ > +#ifdef CONFIG_ARCH_RCU_SYSIDLE_SMALL I don't see any Kconfig creating this new config option. Also, why not simply define this config option unconditionally, with a default of 8, and then use its value directly? > +static int __maybe_unused full_sysidle_state; /* Current system-idle state. > */ > +#define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */ > +#define RCU_SYSIDLE_SHORT1 /* All CPUs idle for brief period. */ > +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ > +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ > +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle > state. */ Perhaps there's a kernel style rule I'm not thinking of that makes it verboten, but: why not use an enum for a state variable like this? - Josh Triplett -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH tip/core/rcu 6/9] nohz_full: Add full-system idle states and variables
From: "Paul E. McKenney" This commit adds control variables and states for full-system idle. The system will progress through the states in numerical order when the system is fully idle (other than the timekeeping CPU), and reset down to the initial state if any non-timekeeping CPU goes non-idle. The current state is kept in full_sysidle_state. A RCU_SYSIDLE_SMALL macro is defined, and systems with this number of CPUs or fewer move through the states more aggressively. The idea is that the resulting memory contention is less of a problem on small systems. Architectures can adjust this value (which defaults to 8) using CONFIG_ARCH_RCU_SYSIDLE_SMALL. One flavor of RCU will be in charge of driving the state machine, defined by rcu_sysidle_state. This should be the busiest flavor of RCU. Signed-off-by: Paul E. McKenney Cc: Frederic Weisbecker Cc: Steven Rostedt --- kernel/rcutree_plugin.h | 28 1 file changed, 28 insertions(+) diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index eab81da..64a05b9f 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2378,6 +2378,34 @@ static void rcu_kick_nohz_cpu(int cpu) #ifdef CONFIG_NO_HZ_FULL_SYSIDLE /* + * Handle small systems specially, accelerating their transition into + * full idle state. Allow arches to override this code's idea of + * what constitutes a "small" system. + */ +#ifdef CONFIG_ARCH_RCU_SYSIDLE_SMALL +#define RCU_SYSIDLE_SMALL CONFIG_ARCH_RCU_SYSIDLE_SMALL +#else /* #ifdef CONFIG_ARCH_RCU_SYSIDLE_SMALL */ +#define RCU_SYSIDLE_SMALL 8 +#endif + +/* + * Define RCU flavor that holds sysidle state. This needs to be the + * most active flavor of RCU. + */ +#ifdef CONFIG_PREEMPT_RCU +static struct rcu_state __maybe_unused *rcu_sysidle_state = _preempt_state; +#else /* #ifdef CONFIG_PREEMPT_RCU */ +static struct rcu_state __maybe_unused *rcu_sysidle_state = _sched_state; +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ + +static int __maybe_unused full_sysidle_state; /* Current system-idle state. */ +#define RCU_SYSIDLE_NOT0 /* Some CPU is not idle. */ +#define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ + +/* * Invoked to note exit from irq or task transition to idle. Note that * usermode execution does -not- count as idle here! After all, we want * to detect full-system idle states, not RCU quiescent states and grace -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH tip/core/rcu 6/9] nohz_full: Add full-system idle states and variables
From: Paul E. McKenney paul...@linux.vnet.ibm.com This commit adds control variables and states for full-system idle. The system will progress through the states in numerical order when the system is fully idle (other than the timekeeping CPU), and reset down to the initial state if any non-timekeeping CPU goes non-idle. The current state is kept in full_sysidle_state. A RCU_SYSIDLE_SMALL macro is defined, and systems with this number of CPUs or fewer move through the states more aggressively. The idea is that the resulting memory contention is less of a problem on small systems. Architectures can adjust this value (which defaults to 8) using CONFIG_ARCH_RCU_SYSIDLE_SMALL. One flavor of RCU will be in charge of driving the state machine, defined by rcu_sysidle_state. This should be the busiest flavor of RCU. Signed-off-by: Paul E. McKenney paul...@linux.vnet.ibm.com Cc: Frederic Weisbecker fweis...@gmail.com Cc: Steven Rostedt rost...@goodmis.org --- kernel/rcutree_plugin.h | 28 1 file changed, 28 insertions(+) diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index eab81da..64a05b9f 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2378,6 +2378,34 @@ static void rcu_kick_nohz_cpu(int cpu) #ifdef CONFIG_NO_HZ_FULL_SYSIDLE /* + * Handle small systems specially, accelerating their transition into + * full idle state. Allow arches to override this code's idea of + * what constitutes a small system. + */ +#ifdef CONFIG_ARCH_RCU_SYSIDLE_SMALL +#define RCU_SYSIDLE_SMALL CONFIG_ARCH_RCU_SYSIDLE_SMALL +#else /* #ifdef CONFIG_ARCH_RCU_SYSIDLE_SMALL */ +#define RCU_SYSIDLE_SMALL 8 +#endif + +/* + * Define RCU flavor that holds sysidle state. This needs to be the + * most active flavor of RCU. + */ +#ifdef CONFIG_PREEMPT_RCU +static struct rcu_state __maybe_unused *rcu_sysidle_state = rcu_preempt_state; +#else /* #ifdef CONFIG_PREEMPT_RCU */ +static struct rcu_state __maybe_unused *rcu_sysidle_state = rcu_sched_state; +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ + +static int __maybe_unused full_sysidle_state; /* Current system-idle state. */ +#define RCU_SYSIDLE_NOT0 /* Some CPU is not idle. */ +#define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ + +/* * Invoked to note exit from irq or task transition to idle. Note that * usermode execution does -not- count as idle here! After all, we want * to detect full-system idle states, not RCU quiescent states and grace -- 1.8.1.5 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH tip/core/rcu 6/9] nohz_full: Add full-system idle states and variables
On Sat, Aug 17, 2013 at 06:49:41PM -0700, Paul E. McKenney wrote: From: Paul E. McKenney paul...@linux.vnet.ibm.com This commit adds control variables and states for full-system idle. The system will progress through the states in numerical order when the system is fully idle (other than the timekeeping CPU), and reset down to the initial state if any non-timekeeping CPU goes non-idle. The current state is kept in full_sysidle_state. A RCU_SYSIDLE_SMALL macro is defined, and systems with this number of CPUs or fewer move through the states more aggressively. The idea is that the resulting memory contention is less of a problem on small systems. Architectures can adjust this value (which defaults to 8) using CONFIG_ARCH_RCU_SYSIDLE_SMALL. One flavor of RCU will be in charge of driving the state machine, defined by rcu_sysidle_state. This should be the busiest flavor of RCU. Signed-off-by: Paul E. McKenney paul...@linux.vnet.ibm.com Cc: Frederic Weisbecker fweis...@gmail.com Cc: Steven Rostedt rost...@goodmis.org One issue (and one question) below; with the issue addressed, Reviewed-by: Josh Triplett j...@joshtriplett.org kernel/rcutree_plugin.h | 28 1 file changed, 28 insertions(+) diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index eab81da..64a05b9f 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2378,6 +2378,34 @@ static void rcu_kick_nohz_cpu(int cpu) #ifdef CONFIG_NO_HZ_FULL_SYSIDLE /* + * Handle small systems specially, accelerating their transition into + * full idle state. Allow arches to override this code's idea of + * what constitutes a small system. + */ +#ifdef CONFIG_ARCH_RCU_SYSIDLE_SMALL I don't see any Kconfig creating this new config option. Also, why not simply define this config option unconditionally, with a default of 8, and then use its value directly? +static int __maybe_unused full_sysidle_state; /* Current system-idle state. */ +#define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */ +#define RCU_SYSIDLE_SHORT1 /* All CPUs idle for brief period. */ +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ Perhaps there's a kernel style rule I'm not thinking of that makes it verboten, but: why not use an enum for a state variable like this? - Josh Triplett -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
