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Message-Id: <20230324001938.3443499-5-paulmck@kernel.org>
Date: Thu, 23 Mar 2023 17:19:24 -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 05/19] srcu: Move ->srcu_size_state from srcu_struct to srcu_usage
This commit moves the ->srcu_size_state 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 | 2 +-
kernel/rcu/srcutree.c | 37 +++++++++++++++++++------------------
2 files changed, 20 insertions(+), 19 deletions(-)
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 362c8f39c53d..72fb01fb2eb5 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -64,13 +64,13 @@ struct srcu_usage {
struct srcu_node *node; /* Combining tree. */
struct srcu_node *level[RCU_NUM_LVLS + 1];
/* First node at each level. */
+ int srcu_size_state; /* Small-to-big transition state. */
};
/*
* Per-SRCU-domain structure, similar in function to rcu_state.
*/
struct srcu_struct {
- 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. */
struct mutex srcu_gp_mutex; /* Serialize GP work. */
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 90d753e10e33..2717217de136 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -225,7 +225,7 @@ static bool init_srcu_struct_nodes(struct srcu_struct *ssp, gfp_t gfp_flags)
}
sdp->grpmask = 1 << (cpu - sdp->mynode->grplo);
}
- smp_store_release(&ssp->srcu_size_state, SRCU_SIZE_WAIT_BARRIER);
+ smp_store_release(&ssp->srcu_sup->srcu_size_state, SRCU_SIZE_WAIT_BARRIER);
return true;
}
@@ -240,7 +240,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
ssp->srcu_sup = kzalloc(sizeof(*ssp->srcu_sup), GFP_KERNEL);
if (!ssp->srcu_sup)
return -ENOMEM;
- ssp->srcu_size_state = SRCU_SIZE_SMALL;
+ ssp->srcu_sup->srcu_size_state = SRCU_SIZE_SMALL;
ssp->srcu_sup->node = NULL;
mutex_init(&ssp->srcu_cb_mutex);
mutex_init(&ssp->srcu_gp_mutex);
@@ -261,7 +261,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
init_srcu_struct_data(ssp);
ssp->srcu_gp_seq_needed_exp = 0;
ssp->srcu_last_gp_end = ktime_get_mono_fast_ns();
- if (READ_ONCE(ssp->srcu_size_state) == SRCU_SIZE_SMALL && SRCU_SIZING_IS_INIT()) {
+ if (READ_ONCE(ssp->srcu_sup->srcu_size_state) == SRCU_SIZE_SMALL && SRCU_SIZING_IS_INIT()) {
if (!init_srcu_struct_nodes(ssp, GFP_ATOMIC)) {
if (!ssp->sda_is_static) {
free_percpu(ssp->sda);
@@ -270,7 +270,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
return -ENOMEM;
}
} else {
- WRITE_ONCE(ssp->srcu_size_state, SRCU_SIZE_BIG);
+ WRITE_ONCE(ssp->srcu_sup->srcu_size_state, SRCU_SIZE_BIG);
}
}
smp_store_release(&ssp->srcu_gp_seq_needed, 0); /* Init done. */
@@ -315,7 +315,7 @@ EXPORT_SYMBOL_GPL(init_srcu_struct);
static void __srcu_transition_to_big(struct srcu_struct *ssp)
{
lockdep_assert_held(&ACCESS_PRIVATE(ssp, lock));
- smp_store_release(&ssp->srcu_size_state, SRCU_SIZE_ALLOC);
+ smp_store_release(&ssp->srcu_sup->srcu_size_state, SRCU_SIZE_ALLOC);
}
/*
@@ -326,10 +326,10 @@ static void srcu_transition_to_big(struct srcu_struct *ssp)
unsigned long flags;
/* Double-checked locking on ->srcu_size-state. */
- if (smp_load_acquire(&ssp->srcu_size_state) != SRCU_SIZE_SMALL)
+ if (smp_load_acquire(&ssp->srcu_sup->srcu_size_state) != SRCU_SIZE_SMALL)
return;
spin_lock_irqsave_rcu_node(ssp, flags);
- if (smp_load_acquire(&ssp->srcu_size_state) != SRCU_SIZE_SMALL) {
+ if (smp_load_acquire(&ssp->srcu_sup->srcu_size_state) != SRCU_SIZE_SMALL) {
spin_unlock_irqrestore_rcu_node(ssp, flags);
return;
}
@@ -345,7 +345,7 @@ static void spin_lock_irqsave_check_contention(struct srcu_struct *ssp)
{
unsigned long j;
- if (!SRCU_SIZING_IS_CONTEND() || ssp->srcu_size_state)
+ if (!SRCU_SIZING_IS_CONTEND() || ssp->srcu_sup->srcu_size_state)
return;
j = jiffies;
if (ssp->srcu_size_jiffies != j) {
@@ -666,7 +666,7 @@ void cleanup_srcu_struct(struct srcu_struct *ssp)
}
kfree(ssp->srcu_sup->node);
ssp->srcu_sup->node = NULL;
- ssp->srcu_size_state = SRCU_SIZE_SMALL;
+ ssp->srcu_sup->srcu_size_state = SRCU_SIZE_SMALL;
if (!ssp->sda_is_static) {
free_percpu(ssp->sda);
ssp->sda = NULL;
@@ -770,7 +770,7 @@ static void srcu_gp_start(struct srcu_struct *ssp)
struct srcu_data *sdp;
int state;
- if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
+ if (smp_load_acquire(&ssp->srcu_sup->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
sdp = per_cpu_ptr(ssp->sda, get_boot_cpu_id());
else
sdp = this_cpu_ptr(ssp->sda);
@@ -880,7 +880,7 @@ static void srcu_gp_end(struct srcu_struct *ssp)
/* A new grace period can start at this point. But only one. */
/* Initiate callback invocation as needed. */
- ss_state = smp_load_acquire(&ssp->srcu_size_state);
+ ss_state = smp_load_acquire(&ssp->srcu_sup->srcu_size_state);
if (ss_state < SRCU_SIZE_WAIT_BARRIER) {
srcu_schedule_cbs_sdp(per_cpu_ptr(ssp->sda, get_boot_cpu_id()),
cbdelay);
@@ -940,7 +940,7 @@ static void srcu_gp_end(struct srcu_struct *ssp)
if (ss_state == SRCU_SIZE_ALLOC)
init_srcu_struct_nodes(ssp, GFP_KERNEL);
else
- smp_store_release(&ssp->srcu_size_state, ss_state + 1);
+ smp_store_release(&ssp->srcu_sup->srcu_size_state, ss_state + 1);
}
}
@@ -1002,7 +1002,7 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp,
unsigned long snp_seq;
/* Ensure that snp node tree is fully initialized before traversing it */
- if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
+ if (smp_load_acquire(&ssp->srcu_sup->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
snp_leaf = NULL;
else
snp_leaf = sdp->mynode;
@@ -1229,7 +1229,7 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp,
* sequence number cannot wrap around in the meantime.
*/
idx = __srcu_read_lock_nmisafe(ssp);
- ss_state = smp_load_acquire(&ssp->srcu_size_state);
+ ss_state = smp_load_acquire(&ssp->srcu_sup->srcu_size_state);
if (ss_state < SRCU_SIZE_WAIT_CALL)
sdp = per_cpu_ptr(ssp->sda, get_boot_cpu_id());
else
@@ -1568,7 +1568,7 @@ void srcu_barrier(struct srcu_struct *ssp)
atomic_set(&ssp->srcu_barrier_cpu_cnt, 1);
idx = __srcu_read_lock_nmisafe(ssp);
- if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
+ if (smp_load_acquire(&ssp->srcu_sup->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, get_boot_cpu_id()));
else
for_each_possible_cpu(cpu)
@@ -1806,7 +1806,7 @@ void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf)
int cpu;
int idx;
unsigned long s0 = 0, s1 = 0;
- int ss_state = READ_ONCE(ssp->srcu_size_state);
+ int ss_state = READ_ONCE(ssp->srcu_sup->srcu_size_state);
int ss_state_idx = ss_state;
idx = ssp->srcu_idx & 0x1;
@@ -1893,8 +1893,9 @@ void __init srcu_init(void)
ssp = list_first_entry(&srcu_boot_list, struct srcu_struct,
work.work.entry);
list_del_init(&ssp->work.work.entry);
- if (SRCU_SIZING_IS(SRCU_SIZING_INIT) && ssp->srcu_size_state == SRCU_SIZE_SMALL)
- ssp->srcu_size_state = SRCU_SIZE_ALLOC;
+ if (SRCU_SIZING_IS(SRCU_SIZING_INIT) &&
+ ssp->srcu_sup->srcu_size_state == SRCU_SIZE_SMALL)
+ ssp->srcu_sup->srcu_size_state = SRCU_SIZE_ALLOC;
queue_work(rcu_gp_wq, &ssp->work.work);
}
}
--
2.40.0.rc2
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