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srcu: Move ->lock from srcu_struct to srcu_usage

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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: Christoph Hellwig <hch@lst.de>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Tested-by: "Zhang, Qiang1" <qiang1.zhang@intel.com>
Tested-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2023-03-17 18:29:38 -07:00
parent 0839ade94b
commit b3fb11f7e9
2 changed files with 35 additions and 32 deletions
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11
include/linux/srcutree.h
View File

@ -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

56
kernel/rcu/srcutree.c
View File

@ -103,7 +103,7 @@ do { \
#define spin_trylock_irqsave_rcu_node(p, flags) \
({ \
bool ___locked = spin_trylock_irqsave(&ACCESS_PRIVATE(p, lock), flags); \
bool ___locked = spin_trylock_irqsave(&ACCESS_PRIVATE(p, lock), flags); \
\
if (___locked) \
smp_mb__after_unlock_lock(); \
@ -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);