srcu: Move ->srcu_gp_mutex from srcu_struct to srcu_usage

This commit moves the ->srcu_gp_mutex 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>

diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 694d87b819175b71bfae03664d7dc2abd64ec857..d04e3da6181c47fe8a4ce3be66d332c4486747be 100644 (file)
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -67,13 +67,13 @@ struct srcu_usage {
        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. */
 };
 
 /*
  * Per-SRCU-domain structure, similar in function to rcu_state.
  */
 struct srcu_struct {
-       struct mutex srcu_gp_mutex;             /* Serialize GP work. */
        unsigned int srcu_idx;                  /* Current rdr array element. */
        unsigned long srcu_gp_seq;              /* Grace-period seq #. */
        unsigned long srcu_gp_seq_needed;       /* Latest gp_seq needed. */

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index c42248cf18f62080a75628020cfcb1c3d7c265d6..a36066798de72d9b39f5750731fb27e9de2b7ae8 100644 (file)
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -245,7 +245,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
        ssp->srcu_sup->srcu_size_state = SRCU_SIZE_SMALL;
        ssp->srcu_sup->node = NULL;
        mutex_init(&ssp->srcu_sup->srcu_cb_mutex);
-       mutex_init(&ssp->srcu_gp_mutex);
+       mutex_init(&ssp->srcu_sup->srcu_gp_mutex);
        ssp->srcu_idx = 0;
        ssp->srcu_gp_seq = 0;
        ssp->srcu_barrier_seq = 0;
@@ -876,7 +876,7 @@ static void srcu_gp_end(struct srcu_struct *ssp)
        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->srcu_sup);
-       mutex_unlock(&ssp->srcu_gp_mutex);
+       mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
        /* A new grace period can start at this point.  But only one. */
 
        /* Initiate callback invocation as needed. */
@@ -1585,7 +1585,7 @@ static void srcu_advance_state(struct srcu_struct *ssp)
 {
        int idx;
 
-       mutex_lock(&ssp->srcu_gp_mutex);
+       mutex_lock(&ssp->srcu_sup->srcu_gp_mutex);
 
        /*
         * Because readers might be delayed for an extended period after
@@ -1603,7 +1603,7 @@ static void srcu_advance_state(struct srcu_struct *ssp)
                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->srcu_sup);
-                       mutex_unlock(&ssp->srcu_gp_mutex);
+                       mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
                        return;
                }
                idx = rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq));
@@ -1611,7 +1611,7 @@ static void srcu_advance_state(struct srcu_struct *ssp)
                        srcu_gp_start(ssp);
                spin_unlock_irq_rcu_node(ssp->srcu_sup);
                if (idx != SRCU_STATE_IDLE) {
-                       mutex_unlock(&ssp->srcu_gp_mutex);
+                       mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
                        return; /* Someone else started the grace period. */
                }
        }
@@ -1619,7 +1619,7 @@ static void srcu_advance_state(struct srcu_struct *ssp)
        if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) == SRCU_STATE_SCAN1) {
                idx = 1 ^ (ssp->srcu_idx & 1);
                if (!try_check_zero(ssp, idx, 1)) {
-                       mutex_unlock(&ssp->srcu_gp_mutex);
+                       mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
                        return; /* readers present, retry later. */
                }
                srcu_flip(ssp);
@@ -1637,7 +1637,7 @@ static void srcu_advance_state(struct srcu_struct *ssp)
                 */
                idx = 1 ^ (ssp->srcu_idx & 1);
                if (!try_check_zero(ssp, idx, 2)) {
-                       mutex_unlock(&ssp->srcu_gp_mutex);
+                       mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
                        return; /* readers present, retry later. */
                }
                ssp->srcu_n_exp_nodelay = 0;