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 <t...@kernel.org>
---
Documentation/kernel-parameters.txt | 9 +++
include/linux/workqueue.h | 5 ++
kernel/workqueue.c | 125 +++++++++++++++++++++++++-----------
3 files changed, 102 insertions(+), 37 deletions(-)
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 @@ bytes respectively. Such letter suffixes can also be
entirely omitted.
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 @@ struct delayed_work {
/*
* 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 0c36327..b48373a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -45,6 +45,7 @@
#include <linux/hashtable.h>
#include <linux/rculist.h>
#include <linux/nodemask.h>
+#include <linux/moduleparam.h>
#include "workqueue_internal.h"
@@ -302,6 +303,9 @@ EXPORT_SYMBOL_GPL(system_unbound_wq);
struct workqueue_struct *system_freezable_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_freezable_wq);
+static bool wq_disable_numa;
+module_param_named(disable_numa, wq_disable_numa, bool, 0444);
+
static int worker_thread(void *__worker);
static void copy_workqueue_attrs(struct workqueue_attrs *to,
const struct workqueue_attrs *from);
@@ -516,21 +520,6 @@ static int worker_pool_assign_id(struct worker_pool *pool)
}
/**
- * first_pwq - return the first pool_workqueue of the specified workqueue
- * @wq: the target workqueue
- *
- * This must be called either with pwq_lock 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_pwq_lock();
- 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
@@ -3101,16 +3090,21 @@ static struct device_attribute wq_sysfs_attrs[] = {
__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;
@@ -3199,10 +3193,52 @@ static ssize_t wq_cpumask_store(struct device *dev,
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 &&
+ wq_numa_possible_cpumask);
+ 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) {
+ if (!v || wq_numa_possible_cpumask) {
+ attrs->no_numa = !v;
+ ret = apply_workqueue_attrs(wq, attrs);
+ } else {
+ printk_ratelimited(KERN_WARNING "workqueue: can't
enable NUMA affinity for \"%s\", disabled system-wide\n",
+ wq->name);
+ }
+ }
+
+ 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,
};
@@ -3725,6 +3761,7 @@ int apply_workqueue_attrs(struct workqueue_struct *wq,
{
struct pool_workqueue **pwq_tbl = NULL, *dfl_pwq = NULL;
struct workqueue_attrs *tmp_attrs = NULL;
+ bool do_numa = !attrs->no_numa && wq_numa_possible_cpumask;
int node;
/* only unbound workqueues can change attributes */
@@ -3740,7 +3777,15 @@ int apply_workqueue_attrs(struct workqueue_struct *wq,
if (!pwq_tbl || !tmp_attrs)
goto enomem;
+ /*
+ * We'll be creating multiple pwqs with differing cpumasks. Make a
+ * copy of @attrs which will be modified and used to obtain pools.
+ * no_numa attribute is special in that it isn't a part of pool
+ * attributes but modifies how pools are selected in this function.
+ * Let's not leak no_numa to pool handling functions.
+ */
copy_workqueue_attrs(tmp_attrs, attrs);
+ tmp_attrs->no_numa = false;
/*
* We want NUMA affinity. For each node with intersecting possible
@@ -3755,7 +3800,7 @@ int apply_workqueue_attrs(struct workqueue_struct *wq,
* Just fall through if NUMA affinity isn't enabled. We'll
* end up using the default pwq which is what we want.
*/
- if (wq_numa_possible_cpumask) {
+ if (do_numa) {
cpumask_and(cpumask, wq_numa_possible_cpumask[node],
attrs->cpumask);
if (cpumask_empty(cpumask))
@@ -4588,22 +4633,28 @@ static int __init init_workqueues(void)
* available. Build one from cpu_to_node() which should have been
* fully initialized by now.
*/
- wq_numa_possible_cpumask = kzalloc(wq_numa_tbl_len *
- sizeof(wq_numa_possible_cpumask[0]),
- GFP_KERNEL);
- BUG_ON(!wq_numa_possible_cpumask);
+ if (!wq_disable_numa) {
+ static cpumask_var_t *tbl;
- for_each_node(node)
- BUG_ON(!alloc_cpumask_var_node(&wq_numa_possible_cpumask[node],
- GFP_KERNEL, node));
- for_each_possible_cpu(cpu) {
- node = cpu_to_node(cpu);
- if (WARN_ON(node == NUMA_NO_NODE)) {
- pr_err("workqueue: NUMA node mapping not available for
cpu%d, disabling NUMA support\n", cpu);
- wq_numa_possible_cpumask = NULL;
- break;
+ tbl = kzalloc(wq_numa_tbl_len * sizeof(tbl[0]), GFP_KERNEL);
+ BUG_ON(!tbl);
+
+ for_each_node(node)
+ BUG_ON(!alloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
+ node));
+ for_each_possible_cpu(cpu) {
+ node = cpu_to_node(cpu);
+ if (WARN_ON(node == NUMA_NO_NODE)) {
+ pr_warn("workqueue: NUMA node mapping not
available for cpu%d, disabling NUMA support\n", cpu);
+ tbl = NULL;
+ break;
+ }
+ cpumask_set_cpu(cpu, tbl[node]);
}
- cpumask_set_cpu(cpu, wq_numa_possible_cpumask[node]);
+
+ wq_numa_possible_cpumask = tbl;
+ } else {
+ pr_info("workqueue: NUMA affinity support disabled\n");
}
/* initialize CPU pools */
--
1.8.1.4
--
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