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| author | Paul E. McKenney <paul.mckenney@linaro.org> | 2011-04-14 12:13:53 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2011-05-05 23:16:55 -0700 |
| commit | 0f962a5e7277c34987b77dc82fc9aefcedc95e27 (patch) | |
| tree | b265d93dcc8f2669f8fb9b353344b9f6cc354728 /kernel/rcutree.c | |
| parent | 27f4d28057adf98750cf863c40baefb12f5b6d21 (diff) | |
| download | lwn-0f962a5e7277c34987b77dc82fc9aefcedc95e27.tar.gz lwn-0f962a5e7277c34987b77dc82fc9aefcedc95e27.zip | |
rcu: Force per-rcu_node kthreads off of the outgoing CPU
The scheduler has had some heartburn in the past when too many real-time
kthreads were affinitied to the outgoing CPU. So, this commit lightens
the load by forcing the per-rcu_node and the boost kthreads off of the
outgoing CPU. Note that RCU's per-CPU kthread remains on the outgoing
CPU until the bitter end, as it must in order to preserve correctness.
Also avoid disabling hardirqs across calls to set_cpus_allowed_ptr(),
given that this function can block.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree.c')
| -rw-r--r-- | kernel/rcutree.c | 24 |
1 files changed, 19 insertions, 5 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 28fd92a9e0d0..51eef4193e7c 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -95,7 +95,7 @@ static DEFINE_PER_CPU(wait_queue_head_t, rcu_cpu_wq); static DEFINE_PER_CPU(char, rcu_cpu_has_work); static char rcu_kthreads_spawnable; -static void rcu_node_kthread_setaffinity(struct rcu_node *rnp); +static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); static void invoke_rcu_cpu_kthread(void); #define RCU_KTHREAD_PRIO 1 /* RT priority for per-CPU kthreads. */ @@ -1099,7 +1099,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) kthread_stop(t); rcu_stop_boost_kthread(rnp); } else - rcu_node_kthread_setaffinity(rnp); + rcu_node_kthread_setaffinity(rnp, -1); } /* @@ -1644,8 +1644,12 @@ static int rcu_node_kthread(void *arg) * Set the per-rcu_node kthread's affinity to cover all CPUs that are * served by the rcu_node in question. The CPU hotplug lock is still * held, so the value of rnp->qsmaskinit will be stable. + * + * We don't include outgoingcpu in the affinity set, use -1 if there is + * no outgoing CPU. If there are no CPUs left in the affinity set, + * this function allows the kthread to execute on any CPU. */ -static void rcu_node_kthread_setaffinity(struct rcu_node *rnp) +static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) { cpumask_var_t cm; int cpu; @@ -1657,8 +1661,14 @@ static void rcu_node_kthread_setaffinity(struct rcu_node *rnp) return; cpumask_clear(cm); for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) - if (mask & 0x1) + if ((mask & 0x1) && cpu != outgoingcpu) cpumask_set_cpu(cpu, cm); + if (cpumask_weight(cm) == 0) { + cpumask_setall(cm); + for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) + cpumask_clear_cpu(cpu, cm); + WARN_ON_ONCE(cpumask_weight(cm) == 0); + } set_cpus_allowed_ptr(rnp->node_kthread_task, cm); rcu_boost_kthread_setaffinity(rnp, cm); free_cpumask_var(cm); @@ -2154,7 +2164,11 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self, rcu_online_kthreads(cpu); break; case CPU_ONLINE: - rcu_node_kthread_setaffinity(rnp); + case CPU_DOWN_FAILED: + rcu_node_kthread_setaffinity(rnp, -1); + break; + case CPU_DOWN_PREPARE: + rcu_node_kthread_setaffinity(rnp, cpu); break; case CPU_DYING: case CPU_DYING_FROZEN: |