diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 8 | ||||
| -rw-r--r-- | include/linux/srcutree.h | 1 | ||||
| -rw-r--r-- | kernel/rcu/srcutree.c | 18 |
3 files changed, 26 insertions, 1 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index facc20a3f962..4a4b9266c4de 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3779,6 +3779,14 @@ spia_pedr= spia_peddr= + srcutree.exp_holdoff [KNL] + Specifies how many nanoseconds must elapse + since the end of the last SRCU grace period for + a given srcu_struct until the next normal SRCU + grace period will be considered for automatic + expediting. Set to zero to disable automatic + expediting. + stacktrace [FTRACE] Enabled the stack tracer on boot up. diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 86df48d3e97b..32e86d85fd11 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -84,6 +84,7 @@ struct srcu_struct { unsigned long srcu_gp_seq; /* Grace-period seq #. */ unsigned long srcu_gp_seq_needed; /* Latest gp_seq needed. */ unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */ + unsigned long srcu_last_gp_end; /* Last GP end timestamp (ns) */ struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */ unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */ struct mutex srcu_barrier_mutex; /* Serialize barrier ops. */ diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 2286e06fd159..74c283f9d15e 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -34,10 +34,14 @@ #include <linux/sched.h> #include <linux/smp.h> #include <linux/delay.h> +#include <linux/module.h> #include <linux/srcu.h> #include "rcu.h" +ulong exp_holdoff = 50 * 1000; /* Holdoff (ns) for auto-expediting. */ +module_param(exp_holdoff, ulong, 0444); + static void srcu_invoke_callbacks(struct work_struct *work); static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay); @@ -145,6 +149,7 @@ static int init_srcu_struct_fields(struct srcu_struct *sp, bool is_static) sp->sda = alloc_percpu(struct srcu_data); init_srcu_struct_nodes(sp, is_static); sp->srcu_gp_seq_needed_exp = 0; + sp->srcu_last_gp_end = ktime_get_mono_fast_ns(); smp_store_release(&sp->srcu_gp_seq_needed, 0); /* Init done. */ return sp->sda ? 0 : -ENOMEM; } @@ -498,6 +503,7 @@ static void srcu_gp_end(struct srcu_struct *sp) idx = rcu_seq_state(sp->srcu_gp_seq); WARN_ON_ONCE(idx != SRCU_STATE_SCAN2); cbdelay = srcu_get_delay(sp); + sp->srcu_last_gp_end = ktime_get_mono_fast_ns(); rcu_seq_end(&sp->srcu_gp_seq); gpseq = rcu_seq_current(&sp->srcu_gp_seq); if (ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, gpseq)) @@ -700,9 +706,10 @@ static void srcu_flip(struct srcu_struct *sp) */ static bool srcu_might_be_idle(struct srcu_struct *sp) { + unsigned long curseq; unsigned long flags; struct srcu_data *sdp; - unsigned long curseq; + unsigned long t; /* If the local srcu_data structure has callbacks, not idle. */ local_irq_save(flags); @@ -718,6 +725,15 @@ static bool srcu_might_be_idle(struct srcu_struct *sp) * Exact information would require acquiring locks, which would * kill scalability, hence the probabalistic nature of the probe. */ + + /* First, see if enough time has passed since the last GP. */ + t = ktime_get_mono_fast_ns(); + if (exp_holdoff == 0 || + time_in_range_open(t, sp->srcu_last_gp_end, + sp->srcu_last_gp_end + exp_holdoff)) + return false; /* Too soon after last GP. */ + + /* Next, check for probable idleness. */ curseq = rcu_seq_current(&sp->srcu_gp_seq); smp_mb(); /* Order ->srcu_gp_seq with ->srcu_gp_seq_needed. */ if (ULONG_CMP_LT(curseq, READ_ONCE(sp->srcu_gp_seq_needed))) |