cpumask: Utility function to set n'th cpu - local cpu first

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>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index d08e4d2a9b92..d5ef249735d2 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