Drivers: hv: Introduce a policy for controlling channel affinity

Introduce a mechanism to control how channels will be affinitized. We will
support two policies:

1. HV_BALANCED: All performance critical channels will be dstributed
evenly amongst all the available NUMA nodes. Once the Node is assigned,
we will assign the CPU based on a simple round robin scheme.

2. HV_LOCALIZED: Only the primary channels are distributed across all
NUMA nodes. Sub-channels will be in the same NUMA node as the primary
channel. This is the current behaviour.

The default policy will be the HV_BALANCED as it can minimize the remote
memory access on NUMA machines with applications that span NUMA nodes.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index e6ef571e6100..c877e7980585 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -674,6 +674,11 @@ enum hv_signal_policy {
 	HV_SIGNAL_POLICY_EXPLICIT,
 };
 
+enum hv_numa_policy {
+	HV_BALANCED = 0,
+	HV_LOCALIZED,
+};
+
 enum vmbus_device_type {
 	HV_IDE = 0,
 	HV_SCSI,
@@ -876,6 +881,18 @@ struct vmbus_channel {
 	 */
 	bool low_latency;
 
+	/*
+	 * NUMA distribution policy:
+	 * We support teo policies:
+	 * 1) Balanced: Here all performance critical channels are
+	 *    distributed evenly amongst all the NUMA nodes.
+	 *    This policy will be the default policy.
+	 * 2) Localized: All channels of a given instance of a
+	 *    performance critical service will be assigned CPUs
+	 *    within a selected NUMA node.
+	 */
+	enum hv_numa_policy affinity_policy;
+
 };
 
 static inline void set_channel_lock_state(struct vmbus_channel *c, bool state)
@@ -895,6 +912,12 @@ static inline void set_channel_signal_state(struct vmbus_channel *c,
 	c->signal_policy = policy;
 }
 
+static inline void set_channel_affinity_state(struct vmbus_channel *c,
+					      enum hv_numa_policy policy)
+{
+	c->affinity_policy = policy;
+}
+
 static inline void set_channel_read_state(struct vmbus_channel *c, bool state)
 {
 	c->batched_reading = state;