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rcu: simplify the usage of percpu data 

&percpu_data is compatible with allocated percpu data.

And we use it and remove the "->rda[NR_CPUS]" array, saving significant
storage on systems with large numbers of CPUs.  This does add an additional
level of indirection and thus an additional cache line referenced, but
because ->rda is not used on the read side, this is OK.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Reviewed-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Lai Jiangshan 2010-06-28 16:25:04 +08:00 committed by Paul E. McKenney
parent e546f485e1
commit 394f99a900
4 changed files with 19 additions and 31 deletions
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42
kernel/rcutree.c
View File

@ -712,7 +712,7 @@ static void
rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
__releases(rcu_get_root(rsp)->lock)
{
struct rcu_data *rdp = rsp->rda[smp_processor_id()];
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
struct rcu_node *rnp = rcu_get_root(rsp);
if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) {
@ -960,7 +960,7 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp)
{
int i;
struct rcu_data *rdp = rsp->rda[smp_processor_id()];
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
if (rdp->nxtlist == NULL)
return; /* irqs disabled, so comparison is stable. */
@ -984,7 +984,7 @@ static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
struct rcu_data *rdp;
raw_spin_lock_irqsave(&rsp->onofflock, flags);
rdp = rsp->rda[smp_processor_id()];
rdp = this_cpu_ptr(rsp->rda);
if (rsp->orphan_cbs_list == NULL) {
raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
return;
@ -1007,7 +1007,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
unsigned long flags;
unsigned long mask;
int need_report = 0;
struct rcu_data *rdp = rsp->rda[cpu];
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp;
/* Exclude any attempts to start a new grace period. */
@ -1226,7 +1226,8 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
cpu = rnp->grplo;
bit = 1;
for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu]))
if ((rnp->qsmask & bit) != 0 &&
f(per_cpu_ptr(rsp->rda, cpu)))
mask |= bit;
}
if (mask != 0) {
@ -1402,7 +1403,7 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
* a quiescent state betweentimes.
*/
local_irq_save(flags);
rdp = rsp->rda[smp_processor_id()];
rdp = this_cpu_ptr(rsp->rda);
rcu_process_gp_end(rsp, rdp);
check_for_new_grace_period(rsp, rdp);
@ -1701,7 +1702,7 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
{
unsigned long flags;
int i;
struct rcu_data *rdp = rsp->rda[cpu];
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp = rcu_get_root(rsp);
/* Set up local state, ensuring consistent view of global state. */
@ -1729,7 +1730,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable)
{
unsigned long flags;
unsigned long mask;
struct rcu_data *rdp = rsp->rda[cpu];
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp = rcu_get_root(rsp);
/* Set up local state, ensuring consistent view of global state. */
@ -1865,7 +1866,8 @@ static void __init rcu_init_levelspread(struct rcu_state *rsp)
/*
* Helper function for rcu_init() that initializes one rcu_state structure.
*/
static void __init rcu_init_one(struct rcu_state *rsp)
static void __init rcu_init_one(struct rcu_state *rsp,
struct rcu_data __percpu *rda)
{
static char *buf[] = { "rcu_node_level_0",
"rcu_node_level_1",
@ -1918,37 +1920,23 @@ static void __init rcu_init_one(struct rcu_state *rsp)
}
}
rsp->rda = rda;
rnp = rsp->level[NUM_RCU_LVLS - 1];
for_each_possible_cpu(i) {
while (i > rnp->grphi)
rnp++;
rsp->rda[i]->mynode = rnp;
per_cpu_ptr(rsp->rda, i)->mynode = rnp;
rcu_boot_init_percpu_data(i, rsp);
}
}
/*
* Helper macro for __rcu_init() and __rcu_init_preempt(). To be used
* nowhere else! Assigns leaf node pointers into each CPU's rcu_data
* structure.
*/
#define RCU_INIT_FLAVOR(rsp, rcu_data) \
do { \
int i; \
\
for_each_possible_cpu(i) { \
(rsp)->rda[i] = &per_cpu(rcu_data, i); \
} \
rcu_init_one(rsp); \
} while (0)
void __init rcu_init(void)
{
int cpu;
rcu_bootup_announce();
RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data);
RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data);
rcu_init_one(&rcu_sched_state, &rcu_sched_data);
rcu_init_one(&rcu_bh_state, &rcu_bh_data);
__rcu_init_preempt();
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);

2
kernel/rcutree.h
View File

@ -283,7 +283,7 @@ struct rcu_state {
struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */
u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */
u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */
struct rcu_data *rda[NR_CPUS]; /* array of rdp pointers. */
struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */
/* The following fields are guarded by the root rcu_node's lock. */

4
kernel/rcutree_plugin.h
View File

@ -154,7 +154,7 @@ static void rcu_preempt_note_context_switch(int cpu)
(t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
/* Possibly blocking in an RCU read-side critical section. */
rdp = rcu_preempt_state.rda[cpu];
rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu);
rnp = rdp->mynode;
raw_spin_lock_irqsave(&rnp->lock, flags);
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
@ -771,7 +771,7 @@ static void rcu_preempt_send_cbs_to_orphanage(void)
*/
static void __init __rcu_init_preempt(void)
{
RCU_INIT_FLAVOR(&rcu_preempt_state, rcu_preempt_data);
rcu_init_one(&rcu_preempt_state, &rcu_preempt_data);
}
/*

2
kernel/rcutree_trace.c
View File

@ -262,7 +262,7 @@ static void print_rcu_pendings(struct seq_file *m, struct rcu_state *rsp)
struct rcu_data *rdp;
for_each_possible_cpu(cpu) {
rdp = rsp->rda[cpu];
rdp = per_cpu_ptr(rsp->rda, cpu);
if (rdp->beenonline)
print_one_rcu_pending(m, rdp);
}