diff mbox

[trusty,SRU,2/5] cpumask: Utility function to set n'th cpu - local cpu first

Message ID 1405693242-3929-3-git-send-email-ming.lei@canonical.com
State New
Headers show

Commit Message

Ming Lei July 18, 2014, 2:20 p.m. UTC 
From: Amir Vadai <amirv@mellanox.com>

This function sets the n'th cpu - local cpu's first.
For example: in a 16 cores server with even cpu's local, will get the
following values:
cpumask_set_cpu_local_first(0, numa, cpumask) => cpu 0 is set
cpumask_set_cpu_local_first(1, numa, cpumask) => cpu 2 is set
...
cpumask_set_cpu_local_first(7, numa, cpumask) => cpu 14 is set
cpumask_set_cpu_local_first(8, numa, cpumask) => cpu 1 is set
cpumask_set_cpu_local_first(9, numa, cpumask) => cpu 3 is set
...
cpumask_set_cpu_local_first(15, numa, cpumask) => cpu 15 is set

Curently this function will be used by multi queue networking devices to
calculate the irq affinity mask, such that as many local cpu's as
possible will be utilized to handle the mq device irq's.

Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit da91309e0a7e8966d916a74cce42ed170fde06bf)
Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 include/linux/cpumask.h |    8 ++++++
 lib/cpumask.c           |   63 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)
diff mbox

Patch

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 3557ea7..2997af6 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -142,6 +142,13 @@  static inline unsigned int cpumask_any_but(const struct cpumask *mask,
 	return 1;
 }
 
+static inline int cpumask_set_cpu_local_first(int i, int numa_node, cpumask_t *dstp)
+{
+	set_bit(0, cpumask_bits(dstp));
+
+	return 0;
+}
+
 #define for_each_cpu(cpu, mask)			\
 	for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
 #define for_each_cpu_not(cpu, mask)		\
@@ -192,6 +199,7 @@  static inline unsigned int cpumask_next_zero(int n, const struct cpumask *srcp)
 
 int cpumask_next_and(int n, const struct cpumask *, const struct cpumask *);
 int cpumask_any_but(const struct cpumask *mask, unsigned int cpu);
+int cpumask_set_cpu_local_first(int i, int numa_node, cpumask_t *dstp);
 
 /**
  * for_each_cpu - iterate over every cpu in a mask
diff --git a/lib/cpumask.c b/lib/cpumask.c
index d327b87..be5f391 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -164,3 +164,66 @@  void __init free_bootmem_cpumask_var(cpumask_var_t mask)
 	free_bootmem(__pa(mask), cpumask_size());
 }
 #endif
+
+/**
+ * cpumask_set_cpu_local_first - set i'th cpu with local numa cpu's first
+ *
+ * @i: index number
+ * @numa_node: local numa_node
+ * @dstp: cpumask with the relevant cpu bit set according to the policy
+ *
+ * This function sets the cpumask according to a numa aware policy.
+ * cpumask could be used as an affinity hint for the IRQ related to a
+ * queue. When the policy is to spread queues across cores - local cores
+ * first.
+ *
+ * Returns 0 on success, -ENOMEM for no memory, and -EAGAIN when failed to set
+ * the cpu bit and need to re-call the function.
+ */
+int cpumask_set_cpu_local_first(int i, int numa_node, cpumask_t *dstp)
+{
+	cpumask_var_t mask;
+	int cpu;
+	int ret = 0;
+
+	if (!zalloc_cpumask_var(&mask, GFP_KERNEL))
+		return -ENOMEM;
+
+	i %= num_online_cpus();
+
+	if (!cpumask_of_node(numa_node)) {
+		/* Use all online cpu's for non numa aware system */
+		cpumask_copy(mask, cpu_online_mask);
+	} else {
+		int n;
+
+		cpumask_and(mask,
+			    cpumask_of_node(numa_node), cpu_online_mask);
+
+		n = cpumask_weight(mask);
+		if (i >= n) {
+			i -= n;
+
+			/* If index > number of local cpu's, mask out local
+			 * cpu's
+			 */
+			cpumask_andnot(mask, cpu_online_mask, mask);
+		}
+	}
+
+	for_each_cpu(cpu, mask) {
+		if (--i < 0)
+			goto out;
+	}
+
+	ret = -EAGAIN;
+
+out:
+	free_cpumask_var(mask);
+
+	if (!ret)
+		cpumask_set_cpu(cpu, dstp);
+
+	return ret;
+}
+EXPORT_SYMBOL(cpumask_set_cpu_local_first);