workqueue: update sysfs interface to reflect NUMA awareness and a kernel param to disable NUMA affinity
Unbound workqueues are now NUMA aware. Let's add some control knobs
and update sysfs interface accordingly.
* Add kernel param workqueue.numa_disable which disables NUMA affinity
globally.
* Replace sysfs file "pool_id" with "pool_ids" which contain
node:pool_id pairs. This change is userland-visible but "pool_id"
hasn't seen a release yet, so this is okay.
* Add a new sysf files "numa" which can toggle NUMA affinity on
individual workqueues. This is implemented as attrs->no_numa whichn
is special in that it isn't part of a pool's attributes. It only
affects how apply_workqueue_attrs() picks which pools to use.
After "pool_ids" change, first_pwq() doesn't have any user left.
Removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4609e81..c75ea0b 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3222,6 +3222,15 @@
or other driver-specific files in the
Documentation/watchdog/ directory.
+ workqueue.disable_numa
+ By default, all work items queued to unbound
+ workqueues are affine to the NUMA nodes they're
+ issued on, which results in better behavior in
+ general. If NUMA affinity needs to be disabled for
+ whatever reason, this option can be used. Note
+ that this also can be controlled per-workqueue for
+ workqueues visible under /sys/bus/workqueue/.
+
x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
default x2apic cluster mode on platforms
supporting x2apic.
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 835d12b..7179756 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -119,10 +119,15 @@
/*
* A struct for workqueue attributes. This can be used to change
* attributes of an unbound workqueue.
+ *
+ * Unlike other fields, ->no_numa isn't a property of a worker_pool. It
+ * only modifies how apply_workqueue_attrs() select pools and thus doesn't
+ * participate in pool hash calculations or equality comparisons.
*/
struct workqueue_attrs {
int nice; /* nice level */
cpumask_var_t cpumask; /* allowed CPUs */
+ bool no_numa; /* disable NUMA affinity */
};
static inline struct delayed_work *to_delayed_work(struct work_struct *work)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 57cd77d..729ac6a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -268,6 +268,9 @@
static cpumask_var_t *wq_numa_possible_cpumask;
/* possible CPUs of each node */
+static bool wq_disable_numa;
+module_param_named(disable_numa, wq_disable_numa, bool, 0444);
+
static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
@@ -517,21 +520,6 @@
}
/**
- * first_pwq - return the first pool_workqueue of the specified workqueue
- * @wq: the target workqueue
- *
- * This must be called either with wq->mutex held or sched RCU read locked.
- * If the pwq needs to be used beyond the locking in effect, the caller is
- * responsible for guaranteeing that the pwq stays online.
- */
-static struct pool_workqueue *first_pwq(struct workqueue_struct *wq)
-{
- assert_rcu_or_wq_mutex(wq);
- return list_first_or_null_rcu(&wq->pwqs, struct pool_workqueue,
- pwqs_node);
-}
-
-/**
* unbound_pwq_by_node - return the unbound pool_workqueue for the given node
* @wq: the target workqueue
* @node: the node ID
@@ -3114,16 +3102,21 @@
__ATTR_NULL,
};
-static ssize_t wq_pool_id_show(struct device *dev,
- struct device_attribute *attr, char *buf)
+static ssize_t wq_pool_ids_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
{
struct workqueue_struct *wq = dev_to_wq(dev);
- struct worker_pool *pool;
- int written;
+ const char *delim = "";
+ int node, written = 0;
rcu_read_lock_sched();
- pool = first_pwq(wq)->pool;
- written = scnprintf(buf, PAGE_SIZE, "%d\n", pool->id);
+ for_each_node(node) {
+ written += scnprintf(buf + written, PAGE_SIZE - written,
+ "%s%d:%d", delim, node,
+ unbound_pwq_by_node(wq, node)->pool->id);
+ delim = " ";
+ }
+ written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
rcu_read_unlock_sched();
return written;
@@ -3212,10 +3205,46 @@
return ret ?: count;
}
+static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct workqueue_struct *wq = dev_to_wq(dev);
+ int written;
+
+ mutex_lock(&wq->mutex);
+ written = scnprintf(buf, PAGE_SIZE, "%d\n",
+ !wq->unbound_attrs->no_numa);
+ mutex_unlock(&wq->mutex);
+
+ return written;
+}
+
+static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct workqueue_struct *wq = dev_to_wq(dev);
+ struct workqueue_attrs *attrs;
+ int v, ret;
+
+ attrs = wq_sysfs_prep_attrs(wq);
+ if (!attrs)
+ return -ENOMEM;
+
+ ret = -EINVAL;
+ if (sscanf(buf, "%d", &v) == 1) {
+ attrs->no_numa = !v;
+ ret = apply_workqueue_attrs(wq, attrs);
+ }
+
+ free_workqueue_attrs(attrs);
+ return ret ?: count;
+}
+
static struct device_attribute wq_sysfs_unbound_attrs[] = {
- __ATTR(pool_id, 0444, wq_pool_id_show, NULL),
+ __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
__ATTR(nice, 0644, wq_nice_show, wq_nice_store),
__ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
+ __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
__ATTR_NULL,
};
@@ -3750,7 +3779,7 @@
static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
int cpu_going_down, cpumask_t *cpumask)
{
- if (!wq_numa_enabled)
+ if (!wq_numa_enabled || attrs->no_numa)
goto use_dfl;
/* does @node have any online CPUs @attrs wants? */
@@ -3951,6 +3980,8 @@
cpumask = target_attrs->cpumask;
mutex_lock(&wq->mutex);
+ if (wq->unbound_attrs->no_numa)
+ goto out_unlock;
copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
pwq = unbound_pwq_by_node(wq, node);
@@ -4763,6 +4794,11 @@
if (num_possible_nodes() <= 1)
return;
+ if (wq_disable_numa) {
+ pr_info("workqueue: NUMA affinity support disabled\n");
+ return;
+ }
+
wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs(GFP_KERNEL);
BUG_ON(!wq_update_unbound_numa_attrs_buf);