diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 8 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 11 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 10 |
3 files changed, 27 insertions, 2 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 500cfa776225..79f2020b0a62 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5018,6 +5018,14 @@ the ->nocb_bypass queue. The definition of "too many" is supplied by this kernel boot parameter. + rcutree.nohz_full_patience_delay= [KNL] + On callback-offloaded (rcu_nocbs) CPUs, avoid + disturbing RCU unless the grace period has + reached the specified age in milliseconds. + Defaults to zero. Large values will be capped + at five seconds. All values will be rounded down + to the nearest value representable by jiffies. + rcutree.qhimark= [KNL] Set threshold of queued RCU callbacks beyond which batch limiting is disabled. diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 18eba61a6f8b..e942dcf51008 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -176,6 +176,9 @@ static int gp_init_delay; module_param(gp_init_delay, int, 0444); static int gp_cleanup_delay; module_param(gp_cleanup_delay, int, 0444); +static int nohz_full_patience_delay; +module_param(nohz_full_patience_delay, int, 0444); +static int nohz_full_patience_delay_jiffies; // Add delay to rcu_read_unlock() for strict grace periods. static int rcu_unlock_delay; @@ -4335,11 +4338,15 @@ static int rcu_pending(int user) return 1; /* Is this a nohz_full CPU in userspace or idle? (Ignore RCU if so.) */ - if ((user || rcu_is_cpu_rrupt_from_idle()) && rcu_nohz_full_cpu()) + gp_in_progress = rcu_gp_in_progress(); + if ((user || rcu_is_cpu_rrupt_from_idle() || + (gp_in_progress && + time_before(jiffies, READ_ONCE(rcu_state.gp_start) + + nohz_full_patience_delay_jiffies))) && + rcu_nohz_full_cpu()) return 0; /* Is the RCU core waiting for a quiescent state from this CPU? */ - gp_in_progress = rcu_gp_in_progress(); if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm && gp_in_progress) return 1; diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 340bbefe5f65..009ce0320f7f 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -93,6 +93,16 @@ static void __init rcu_bootup_announce_oddness(void) pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_init_delay); if (gp_cleanup_delay) pr_info("\tRCU debug GP cleanup slowdown %d jiffies.\n", gp_cleanup_delay); + if (nohz_full_patience_delay < 0) { + pr_info("\tRCU NOCB CPU patience negative (%d), resetting to zero.\n", nohz_full_patience_delay); + nohz_full_patience_delay = 0; + } else if (nohz_full_patience_delay > 5 * MSEC_PER_SEC) { + pr_info("\tRCU NOCB CPU patience too large (%d), resetting to %ld.\n", nohz_full_patience_delay, 5 * MSEC_PER_SEC); + nohz_full_patience_delay = 5 * MSEC_PER_SEC; + } else if (nohz_full_patience_delay) { + pr_info("\tRCU NOCB CPU patience set to %d milliseconds.\n", nohz_full_patience_delay); + } + nohz_full_patience_delay_jiffies = msecs_to_jiffies(nohz_full_patience_delay); if (!use_softirq) pr_info("\tRCU_SOFTIRQ processing moved to rcuc kthreads.\n"); if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG)) |