This patchset adds a new CPU mask for SMP systems to the irq_desc
struct. It also exposes an API for underlying device drivers to
assist irqbalance in making smarter decisions when balancing, especially
in a NUMA environment. For example, an ethernet driver with MSI-X may
wish to limit the CPUs that an interrupt can be balanced within to
stay on a single NUMA node. Current irqbalance operation can move the
interrupt off the node, resulting in cross-node memory accesses and
locks.
The API is a get/set API within the kernel, along with a /proc entry
for the interrupt.
Signed-off-by: Peter P Waskiewicz Jr <[email protected]>
---
include/linux/interrupt.h | 8 ++++++
include/linux/irq.h | 2 ++
kernel/irq/manage.c | 32 +++++++++++++++++++++++++
kernel/irq/proc.c | 57 +++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 99 insertions(+), 0 deletions(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 75f3f00..9fd08aa 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -208,6 +208,8 @@ extern cpumask_var_t irq_default_affinity;
extern int irq_set_affinity(unsigned int irq, const struct cpumask *cpumask);
extern int irq_can_set_affinity(unsigned int irq);
extern int irq_select_affinity(unsigned int irq);
+extern int irq_set_node_affinity(unsigned int irq,
+ const struct cpumask *cpumask);
#else /* CONFIG_SMP */
@@ -223,6 +225,12 @@ static inline int irq_can_set_affinity(unsigned int irq)
static inline int irq_select_affinity(unsigned int irq) { return 0; }
+static inline int irq_set_node_affinity(unsigned int irq,
+ const struct cpumask *m)
+{
+ return -EINVAL;
+}
+
#endif /* CONFIG_SMP && CONFIG_GENERIC_HARDIRQS */
#ifdef CONFIG_GENERIC_HARDIRQS
diff --git a/include/linux/irq.h b/include/linux/irq.h
index ae9653d..26d7d07 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -166,6 +166,7 @@ struct irq_2_iommu;
* @lock: locking for SMP
* @affinity: IRQ affinity on SMP
* @node: node index useful for balancing
+ * @node_affinity: irq mask hints for irqbalance
* @pending_mask: pending rebalanced interrupts
* @threads_active: number of irqaction threads currently running
* @wait_for_threads: wait queue for sync_irq to wait for threaded handlers
@@ -196,6 +197,7 @@ struct irq_desc {
#ifdef CONFIG_SMP
cpumask_var_t affinity;
unsigned int node;
+ cpumask_var_t node_affinity;
#ifdef CONFIG_GENERIC_PENDING_IRQ
cpumask_var_t pending_mask;
#endif
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 7305b29..9e80783 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -138,6 +138,38 @@ int irq_set_affinity(unsigned int irq, const struct cpumask *cpumask)
return 0;
}
+/**
+ * irq_set_node_affinity - Set the CPU mask this interrupt can run on
+ * @irq: Interrupt to modify
+ * @cpumask: CPU mask to assign to the interrupt
+ *
+ */
+int irq_set_node_affinity(unsigned int irq, const struct cpumask *cpumask)
+{
+ struct irq_desc *desc = irq_to_desc(irq);
+ unsigned long flags;
+
+ spin_lock_irqsave(&desc->lock, flags);
+ cpumask_copy(desc->node_affinity, cpumask);
+ spin_unlock_irqrestore(&desc->lock, flags);
+
+ return 0;
+}
+EXPORT_SYMBOL(irq_set_node_affinity);
+
+/**
+ * irq_get_node_affinity - Get the CPU mask this interrupt can run on
+ * @irq: Interrupt to get information
+ *
+ */
+struct cpumask *irq_get_node_affinity(unsigned int irq)
+{
+ struct irq_desc *desc = irq_to_desc(irq);
+
+ return desc->node_affinity;
+}
+EXPORT_SYMBOL(irq_get_node_affinity);
+
#ifndef CONFIG_AUTO_IRQ_AFFINITY
/*
* Generic version of the affinity autoselector.
diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index 0832145..192e3fb 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -31,6 +31,16 @@ static int irq_affinity_proc_show(struct seq_file *m, void *v)
return 0;
}
+static int irq_node_affinity_proc_show(struct seq_file *m, void *v)
+{
+ struct irq_desc *desc = irq_to_desc((long)m->private);
+ const struct cpumask *mask = desc->node_affinity;
+
+ seq_cpumask(m, mask);
+ seq_putc(m, '\n');
+ return 0;
+}
+
#ifndef is_affinity_mask_valid
#define is_affinity_mask_valid(val) 1
#endif
@@ -78,11 +88,46 @@ free_cpumask:
return err;
}
+static ssize_t irq_node_affinity_proc_write(struct file *file,
+ const char __user *buffer, size_t count, loff_t *pos)
+{
+ unsigned int irq = (int)(long)PDE(file->f_path.dentry->d_inode)->data;
+ cpumask_var_t new_value;
+ int err;
+
+ if (no_irq_affinity || irq_balancing_disabled(irq))
+ return -EIO;
+
+ if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
+ return -ENOMEM;
+
+ err = cpumask_parse_user(buffer, count, new_value);
+ if (err)
+ goto free_cpumask;
+
+ if (!is_affinity_mask_valid(new_value)) {
+ err = -EINVAL;
+ goto free_cpumask;
+ }
+
+ irq_set_node_affinity(irq, new_value);
+ err = count;
+
+free_cpumask:
+ free_cpumask_var(new_value);
+ return err;
+}
+
static int irq_affinity_proc_open(struct inode *inode, struct file *file)
{
return single_open(file, irq_affinity_proc_show, PDE(inode)->data);
}
+static int irq_node_affinity_proc_open(struct inode *inode, struct file *f)
+{
+ return single_open(f, irq_node_affinity_proc_show, PDE(inode)->data);
+}
+
static const struct file_operations irq_affinity_proc_fops = {
.open = irq_affinity_proc_open,
.read = seq_read,
@@ -91,6 +136,14 @@ static const struct file_operations irq_affinity_proc_fops = {
.write = irq_affinity_proc_write,
};
+static const struct file_operations irq_node_affinity_proc_fops = {
+ .open = irq_node_affinity_proc_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+ .write = irq_node_affinity_proc_write,
+};
+
static int default_affinity_show(struct seq_file *m, void *v)
{
seq_cpumask(m, irq_default_affinity);
@@ -230,6 +283,10 @@ void register_irq_proc(unsigned int irq, struct irq_desc *desc)
/* create /proc/irq/<irq>/smp_affinity */
proc_create_data("smp_affinity", 0600, desc->dir,
&irq_affinity_proc_fops, (void *)(long)irq);
+
+ /* create /proc/irq/<irq>/node_affinity */
+ proc_create_data("node_affinity", 0600, desc->dir,
+ &irq_node_affinity_proc_fops, (void *)(long)irq);
#endif
proc_create_data("spurious", 0444, desc->dir,