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Commit 509879bd authored by K. Y. Srinivasan's avatar K. Y. Srinivasan Committed by Greg Kroah-Hartman
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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: default avatarK. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent bb08d431

drivers/hv/channel_mgmt.c

+39 −29
Original line number Diff line number Diff line
@@ -356,6 +356,7 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid) 
	 * We need to free the bit for init_vp_index() to work in the case

	 * of sub-channel, when we reload drivers like hv_netvsc.

	 */

	if (channel->affinity_policy == HV_LOCALIZED)

		cpumask_clear_cpu(channel->target_cpu,

				  &primary_channel->alloced_cpus_in_node);
@@ -548,17 +549,17 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type) 
	}



	/*

	 * We distribute primary channels evenly across all the available

	 * NUMA nodes and within the assigned NUMA node we will assign the

	 * first available CPU to the primary channel.

	 * The sub-channels will be assigned to the CPUs available in the

	 * NUMA node evenly.

	 * Based on the channel affinity policy, we will assign the NUMA

	 * nodes.

	 */

	if (!primary) {



	if ((channel->affinity_policy == HV_BALANCED) || (!primary)) {

		while (true) {

			next_node = next_numa_node_id++;

			if (next_node == nr_node_ids)

			if (next_node == nr_node_ids) {

				next_node = next_numa_node_id = 0;

				continue;

			}

			if (cpumask_empty(cpumask_of_node(next_node)))

				continue;

			break;
@@ -582,15 +583,17 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type) 


	cur_cpu = -1;



	if (primary->affinity_policy == HV_LOCALIZED) {

		/*

	 * Normally Hyper-V host doesn't create more subchannels than there

	 * are VCPUs on the node but it is possible when not all present VCPUs

	 * on the node are initialized by guest. Clear the alloced_cpus_in_node

	 * to start over.

		 * Normally Hyper-V host doesn't create more subchannels

		 * than there are VCPUs on the node but it is possible when not

		 * all present VCPUs on the node are initialized by guest.

		 * Clear the alloced_cpus_in_node to start over.

		 */

		if (cpumask_equal(&primary->alloced_cpus_in_node,

				  cpumask_of_node(primary->numa_node)))

			cpumask_clear(&primary->alloced_cpus_in_node);

	}



	while (true) {

		cur_cpu = cpumask_next(cur_cpu, &available_mask);
@@ -601,11 +604,14 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type) 
			continue;

		}



		if (primary->affinity_policy == HV_LOCALIZED) {

			/*

		 * NOTE: in the case of sub-channel, we clear the sub-channel

		 * related bit(s) in primary->alloced_cpus_in_node in

		 * hv_process_channel_removal(), so when we reload drivers

		 * like hv_netvsc in SMP guest, here we're able to re-allocate

			 * NOTE: in the case of sub-channel, we clear the

			 * sub-channel related bit(s) in

			 * primary->alloced_cpus_in_node in

			 * hv_process_channel_removal(), so when we

			 * reload drivers like hv_netvsc in SMP guest, here

			 * we're able to re-allocate

			 * bit from primary->alloced_cpus_in_node.

			 */

			if (!cpumask_test_cpu(cur_cpu,
@@ -615,6 +621,10 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type) 
				cpumask_set_cpu(cur_cpu, alloced_mask);

				break;

			}

		} else {

			cpumask_set_cpu(cur_cpu, alloced_mask);

			break;

		}

	}



	channel->target_cpu = cur_cpu;

include/linux/hyperv.h

+23 −0
Original line number Diff line number Diff line
@@ -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;