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Message-Id: <20230324001938.3443499-8-paulmck@kernel.org>
Date: Thu, 23 Mar 2023 17:19:27 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, kernel-team@...a.com,
rostedt@...dmis.org, hch@....de,
"Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH RFC rcu 08/19] 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: Christoph Hellwig <hch@....de>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
include/linux/srcutree.h | 11 +++++---
kernel/rcu/srcutree.c | 56 ++++++++++++++++++++--------------------
2 files changed, 35 insertions(+), 32 deletions(-)
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 69d49de87b67..6fe5743c1179 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -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 #. */
@@ -129,7 +129,6 @@ 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, \
@@ -167,7 +166,9 @@ 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 \
@@ -175,7 +176,9 @@ 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
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index f6f37e34a1e0..579c43ff0f4b 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -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);
}
/*
@@ -1621,17 +1621,17 @@ 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. */
@@ -1645,10 +1645,10 @@ 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) {
@@ -1732,7 +1732,7 @@ 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. */
@@ -1742,7 +1742,7 @@ 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);
--
2.40.0.rc2
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