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authorAmir Vadai <amirv@mellanox.com>2014-05-25 17:47:26 +0300
committerDavid S. Miller <davem@davemloft.net>2014-06-01 19:16:29 -0700
commitc8865b64b05b2f4eeefd369373e9c8aeb069e7a1 (patch)
treefef93ad82529c709aeb8d15fb4330631918698d9
parent90d0e08e574d1aa8553ee6179fcf3bf2b333ca6d (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>
-rw-r--r--include/linux/cpumask.h2
-rw-r--r--lib/cpumask.c64
2 files changed, 66 insertions, 0 deletions
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index d08e4d2a9b92..3551d667ef9f 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -257,6 +257,8 @@ static inline void cpumask_set_cpu(unsigned int cpu, struct cpumask *dstp)
set_bit(cpumask_check(cpu), cpumask_bits(dstp));
}
+int cpumask_set_cpu_local_first(int i, int numa_node, cpumask_t *dstp);
+
/**
* cpumask_clear_cpu - clear a cpu in a cpumask
* @cpu: cpu number (< nr_cpu_ids)
diff --git a/lib/cpumask.c b/lib/cpumask.c
index b810b753c607..14049a96f04a 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -163,4 +163,68 @@ void __init free_bootmem_cpumask_var(cpumask_var_t mask)
{
memblock_free_early(__pa(mask), cpumask_size());
}
+
+/**
+ * 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);
+
#endif

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