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authorAmir Vadai <amirv@mellanox.com>2014-06-09 10:24:38 +0300
committerDavid S. Miller <davem@davemloft.net>2014-06-11 14:58:16 -0700
commitda91309e0a7e8966d916a74cce42ed170fde06bf (patch)
tree71bb5b4da988abb97d1a696c2f64bf39ecf9ae0d /lib/cpumask.c
parentd4f3862017f9aaa1a6b6bade396a99a4b77e2cb2 (diff)
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>
Diffstat (limited to 'lib/cpumask.c')
-rw-r--r--lib/cpumask.c63
1 files changed, 63 insertions, 0 deletions
diff --git a/lib/cpumask.c b/lib/cpumask.c
index b810b753c607..c101230658eb 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -164,3 +164,66 @@ void __init free_bootmem_cpumask_var(cpumask_var_t mask)
memblock_free_early(__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);

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