Commit b3fb11f7 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

srcu: Move ->lock from srcu_struct to srcu_usage 



This commit moves the ->lock field from the srcu_struct structure to
the srcu_usage structure to reduce the size of the former in order to
improve cache locality.

Suggested-by: default avatarChristoph Hellwig <hch@lst.de>
Tested-by: default avatarSachin Sant <sachinp@linux.ibm.com>
Tested-by: default avatar"Zhang, Qiang1" <qiang1.zhang@intel.com>
Tested-by: default avatarJoel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 0839ade9

include/linux/srcutree.h

+7 −4
Original line number Diff line number Diff line
@@ -66,13 +66,13 @@ struct srcu_usage { 
						/* First node at each level. */

	int srcu_size_state;			/* Small-to-big transition state. */

	struct mutex srcu_cb_mutex;		/* Serialize CB preparation. */

	spinlock_t __private lock;		/* Protect counters and size state. */

};



/*

 * Per-SRCU-domain structure, similar in function to rcu_state.

 */

struct srcu_struct {

	spinlock_t __private lock;		/* Protect counters and size state. */

	struct mutex srcu_gp_mutex;		/* Serialize GP work. */

	unsigned int srcu_idx;			/* Current rdr array element. */

	unsigned long srcu_gp_seq;		/* Grace-period seq #. */
@@ -116,7 +116,6 @@ struct srcu_struct { 
#define SRCU_STATE_SCAN2	2



#define __SRCU_STRUCT_INIT_COMMON(name, usage_name)						\

	.lock = __SPIN_LOCK_UNLOCKED(name.lock),						\

	.srcu_gp_seq_needed = -1UL,								\

	.work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0),					\

	.srcu_sup = &usage_name,								\
@@ -154,7 +153,9 @@ struct srcu_struct { 
 */

#ifdef MODULE

# define __DEFINE_SRCU(name, is_static)								\

	static struct srcu_usage name##_srcu_usage;						\

	static struct srcu_usage name##_srcu_usage = {						\

		.lock = __SPIN_LOCK_UNLOCKED(name.lock),					\

	};											\

	is_static struct srcu_struct name = __SRCU_STRUCT_INIT_MODULE(name, name##_srcu_usage);	\

	extern struct srcu_struct * const __srcu_struct_##name;					\

	struct srcu_struct * const __srcu_struct_##name						\
@@ -162,7 +163,9 @@ struct srcu_struct { 
#else

# define __DEFINE_SRCU(name, is_static)								\

	static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);				\

	static struct srcu_usage name##_srcu_usage;						\

	static struct srcu_usage name##_srcu_usage = {						\

		.lock = __SPIN_LOCK_UNLOCKED(name.lock),					\

	};											\

	is_static struct srcu_struct name =							\

		__SRCU_STRUCT_INIT(name, name##_srcu_usage, name##_srcu_data)

#endif

kernel/rcu/srcutree.c

+28 −28
Original line number Diff line number Diff line
@@ -241,7 +241,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static) 
	if (!ssp->srcu_sup)

		return -ENOMEM;

	if (!is_static)

		spin_lock_init(&ACCESS_PRIVATE(ssp, lock));

		spin_lock_init(&ACCESS_PRIVATE(ssp->srcu_sup, lock));

	ssp->srcu_sup->srcu_size_state = SRCU_SIZE_SMALL;

	ssp->srcu_sup->node = NULL;

	mutex_init(&ssp->srcu_sup->srcu_cb_mutex);
@@ -314,7 +314,7 @@ EXPORT_SYMBOL_GPL(init_srcu_struct); 
 */

static void __srcu_transition_to_big(struct srcu_struct *ssp)

{

	lockdep_assert_held(&ACCESS_PRIVATE(ssp, lock));

	lockdep_assert_held(&ACCESS_PRIVATE(ssp->srcu_sup, lock));

	smp_store_release(&ssp->srcu_sup->srcu_size_state, SRCU_SIZE_ALLOC);

}
@@ -328,13 +328,13 @@ static void srcu_transition_to_big(struct srcu_struct *ssp) 
	/* Double-checked locking on ->srcu_size-state. */

	if (smp_load_acquire(&ssp->srcu_sup->srcu_size_state) != SRCU_SIZE_SMALL)

		return;

	spin_lock_irqsave_rcu_node(ssp, flags);

	spin_lock_irqsave_rcu_node(ssp->srcu_sup, flags);

	if (smp_load_acquire(&ssp->srcu_sup->srcu_size_state) != SRCU_SIZE_SMALL) {

		spin_unlock_irqrestore_rcu_node(ssp, flags);

		spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);

		return;

	}

	__srcu_transition_to_big(ssp);

	spin_unlock_irqrestore_rcu_node(ssp, flags);

	spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);

}



/*
@@ -369,9 +369,9 @@ static void spin_lock_irqsave_sdp_contention(struct srcu_data *sdp, unsigned lon 


	if (spin_trylock_irqsave_rcu_node(sdp, *flags))

		return;

	spin_lock_irqsave_rcu_node(ssp, *flags);

	spin_lock_irqsave_rcu_node(ssp->srcu_sup, *flags);

	spin_lock_irqsave_check_contention(ssp);

	spin_unlock_irqrestore_rcu_node(ssp, *flags);

	spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, *flags);

	spin_lock_irqsave_rcu_node(sdp, *flags);

}
@@ -383,9 +383,9 @@ static void spin_lock_irqsave_sdp_contention(struct srcu_data *sdp, unsigned lon 
 */

static void spin_lock_irqsave_ssp_contention(struct srcu_struct *ssp, unsigned long *flags)

{

	if (spin_trylock_irqsave_rcu_node(ssp, *flags))

	if (spin_trylock_irqsave_rcu_node(ssp->srcu_sup, *flags))

		return;

	spin_lock_irqsave_rcu_node(ssp, *flags);

	spin_lock_irqsave_rcu_node(ssp->srcu_sup, *flags);

	spin_lock_irqsave_check_contention(ssp);

}
@@ -404,13 +404,13 @@ static void check_init_srcu_struct(struct srcu_struct *ssp) 
	/* The smp_load_acquire() pairs with the smp_store_release(). */

	if (!rcu_seq_state(smp_load_acquire(&ssp->srcu_gp_seq_needed))) /*^^^*/

		return; /* Already initialized. */

	spin_lock_irqsave_rcu_node(ssp, flags);

	spin_lock_irqsave_rcu_node(ssp->srcu_sup, flags);

	if (!rcu_seq_state(ssp->srcu_gp_seq_needed)) {

		spin_unlock_irqrestore_rcu_node(ssp, flags);

		spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);

		return;

	}

	init_srcu_struct_fields(ssp, true);

	spin_unlock_irqrestore_rcu_node(ssp, flags);

	spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);

}



/*
@@ -774,7 +774,7 @@ static void srcu_gp_start(struct srcu_struct *ssp) 
		sdp = per_cpu_ptr(ssp->sda, get_boot_cpu_id());

	else

		sdp = this_cpu_ptr(ssp->sda);

	lockdep_assert_held(&ACCESS_PRIVATE(ssp, lock));

	lockdep_assert_held(&ACCESS_PRIVATE(ssp->srcu_sup, lock));

	WARN_ON_ONCE(ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed));

	spin_lock_rcu_node(sdp);  /* Interrupts already disabled. */

	rcu_segcblist_advance(&sdp->srcu_cblist,
@@ -864,7 +864,7 @@ static void srcu_gp_end(struct srcu_struct *ssp) 
	mutex_lock(&ssp->srcu_sup->srcu_cb_mutex);



	/* End the current grace period. */

	spin_lock_irq_rcu_node(ssp);

	spin_lock_irq_rcu_node(ssp->srcu_sup);

	idx = rcu_seq_state(ssp->srcu_gp_seq);

	WARN_ON_ONCE(idx != SRCU_STATE_SCAN2);

	if (ULONG_CMP_LT(READ_ONCE(ssp->srcu_gp_seq), READ_ONCE(ssp->srcu_gp_seq_needed_exp)))
@@ -875,7 +875,7 @@ static void srcu_gp_end(struct srcu_struct *ssp) 
	gpseq = rcu_seq_current(&ssp->srcu_gp_seq);

	if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, gpseq))

		WRITE_ONCE(ssp->srcu_gp_seq_needed_exp, gpseq);

	spin_unlock_irq_rcu_node(ssp);

	spin_unlock_irq_rcu_node(ssp->srcu_sup);

	mutex_unlock(&ssp->srcu_gp_mutex);

	/* A new grace period can start at this point.  But only one. */
@@ -924,15 +924,15 @@ static void srcu_gp_end(struct srcu_struct *ssp) 
	mutex_unlock(&ssp->srcu_sup->srcu_cb_mutex);



	/* Start a new grace period if needed. */

	spin_lock_irq_rcu_node(ssp);

	spin_lock_irq_rcu_node(ssp->srcu_sup);

	gpseq = rcu_seq_current(&ssp->srcu_gp_seq);

	if (!rcu_seq_state(gpseq) &&

	    ULONG_CMP_LT(gpseq, ssp->srcu_gp_seq_needed)) {

		srcu_gp_start(ssp);

		spin_unlock_irq_rcu_node(ssp);

		spin_unlock_irq_rcu_node(ssp->srcu_sup);

		srcu_reschedule(ssp, 0);

	} else {

		spin_unlock_irq_rcu_node(ssp);

		spin_unlock_irq_rcu_node(ssp->srcu_sup);

	}



	/* Transition to big if needed. */
@@ -975,7 +975,7 @@ static void srcu_funnel_exp_start(struct srcu_struct *ssp, struct srcu_node *snp 
	spin_lock_irqsave_ssp_contention(ssp, &flags);

	if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, s))

		WRITE_ONCE(ssp->srcu_gp_seq_needed_exp, s);

	spin_unlock_irqrestore_rcu_node(ssp, flags);

	spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);

}



/*
@@ -1064,7 +1064,7 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp, 
		else if (list_empty(&ssp->work.work.entry))

			list_add(&ssp->work.work.entry, &srcu_boot_list);

	}

	spin_unlock_irqrestore_rcu_node(ssp, flags);

	spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags);

}



/*
@@ -1599,17 +1599,17 @@ static void srcu_advance_state(struct srcu_struct *ssp) 
	 */

	idx = rcu_seq_state(smp_load_acquire(&ssp->srcu_gp_seq)); /* ^^^ */

	if (idx == SRCU_STATE_IDLE) {

		spin_lock_irq_rcu_node(ssp);

		spin_lock_irq_rcu_node(ssp->srcu_sup);

		if (ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed)) {

			WARN_ON_ONCE(rcu_seq_state(ssp->srcu_gp_seq));

			spin_unlock_irq_rcu_node(ssp);

			spin_unlock_irq_rcu_node(ssp->srcu_sup);

			mutex_unlock(&ssp->srcu_gp_mutex);

			return;

		}

		idx = rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq));

		if (idx == SRCU_STATE_IDLE)

			srcu_gp_start(ssp);

		spin_unlock_irq_rcu_node(ssp);

		spin_unlock_irq_rcu_node(ssp->srcu_sup);

		if (idx != SRCU_STATE_IDLE) {

			mutex_unlock(&ssp->srcu_gp_mutex);

			return; /* Someone else started the grace period. */
@@ -1623,10 +1623,10 @@ static void srcu_advance_state(struct srcu_struct *ssp) 
			return; /* readers present, retry later. */

		}

		srcu_flip(ssp);

		spin_lock_irq_rcu_node(ssp);

		spin_lock_irq_rcu_node(ssp->srcu_sup);

		rcu_seq_set_state(&ssp->srcu_gp_seq, SRCU_STATE_SCAN2);

		ssp->srcu_n_exp_nodelay = 0;

		spin_unlock_irq_rcu_node(ssp);

		spin_unlock_irq_rcu_node(ssp->srcu_sup);

	}



	if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) == SRCU_STATE_SCAN2) {
@@ -1710,7 +1710,7 @@ static void srcu_reschedule(struct srcu_struct *ssp, unsigned long delay) 
{

	bool pushgp = true;



	spin_lock_irq_rcu_node(ssp);

	spin_lock_irq_rcu_node(ssp->srcu_sup);

	if (ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed)) {

		if (!WARN_ON_ONCE(rcu_seq_state(ssp->srcu_gp_seq))) {

			/* All requests fulfilled, time to go idle. */
@@ -1720,7 +1720,7 @@ static void srcu_reschedule(struct srcu_struct *ssp, unsigned long delay) 
		/* Outstanding request and no GP.  Start one. */

		srcu_gp_start(ssp);

	}

	spin_unlock_irq_rcu_node(ssp);

	spin_unlock_irq_rcu_node(ssp->srcu_sup);



	if (pushgp)

		queue_delayed_work(rcu_gp_wq, &ssp->work, delay);