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>
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@ -356,8 +356,9 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
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* We need to free the bit for init_vp_index() to work in the case
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* of sub-channel, when we reload drivers like hv_netvsc.
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*/
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cpumask_clear_cpu(channel->target_cpu,
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&primary_channel->alloced_cpus_in_node);
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if (channel->affinity_policy == HV_LOCALIZED)
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cpumask_clear_cpu(channel->target_cpu,
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&primary_channel->alloced_cpus_in_node);
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vmbus_release_relid(relid);
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@ -548,17 +549,17 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
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}
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/*
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* We distribute primary channels evenly across all the available
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* NUMA nodes and within the assigned NUMA node we will assign the
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* first available CPU to the primary channel.
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* The sub-channels will be assigned to the CPUs available in the
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* NUMA node evenly.
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* Based on the channel affinity policy, we will assign the NUMA
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* nodes.
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*/
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if (!primary) {
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if ((channel->affinity_policy == HV_BALANCED) || (!primary)) {
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while (true) {
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next_node = next_numa_node_id++;
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if (next_node == nr_node_ids)
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if (next_node == nr_node_ids) {
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next_node = next_numa_node_id = 0;
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continue;
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}
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if (cpumask_empty(cpumask_of_node(next_node)))
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continue;
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break;
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@ -582,15 +583,17 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
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cur_cpu = -1;
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/*
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* Normally Hyper-V host doesn't create more subchannels than there
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* are VCPUs on the node but it is possible when not all present VCPUs
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* on the node are initialized by guest. Clear the alloced_cpus_in_node
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* to start over.
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*/
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if (cpumask_equal(&primary->alloced_cpus_in_node,
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cpumask_of_node(primary->numa_node)))
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cpumask_clear(&primary->alloced_cpus_in_node);
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if (primary->affinity_policy == HV_LOCALIZED) {
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/*
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* Normally Hyper-V host doesn't create more subchannels
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* than there are VCPUs on the node but it is possible when not
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* all present VCPUs on the node are initialized by guest.
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* Clear the alloced_cpus_in_node to start over.
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*/
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if (cpumask_equal(&primary->alloced_cpus_in_node,
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cpumask_of_node(primary->numa_node)))
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cpumask_clear(&primary->alloced_cpus_in_node);
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}
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while (true) {
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cur_cpu = cpumask_next(cur_cpu, &available_mask);
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@ -601,17 +604,24 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
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continue;
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}
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/*
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* NOTE: in the case of sub-channel, we clear the sub-channel
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* related bit(s) in primary->alloced_cpus_in_node in
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* hv_process_channel_removal(), so when we reload drivers
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* like hv_netvsc in SMP guest, here we're able to re-allocate
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* bit from primary->alloced_cpus_in_node.
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*/
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if (!cpumask_test_cpu(cur_cpu,
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&primary->alloced_cpus_in_node)) {
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cpumask_set_cpu(cur_cpu,
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&primary->alloced_cpus_in_node);
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if (primary->affinity_policy == HV_LOCALIZED) {
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/*
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* NOTE: in the case of sub-channel, we clear the
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* sub-channel related bit(s) in
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* primary->alloced_cpus_in_node in
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* hv_process_channel_removal(), so when we
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* reload drivers like hv_netvsc in SMP guest, here
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* we're able to re-allocate
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* bit from primary->alloced_cpus_in_node.
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*/
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if (!cpumask_test_cpu(cur_cpu,
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&primary->alloced_cpus_in_node)) {
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cpumask_set_cpu(cur_cpu,
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&primary->alloced_cpus_in_node);
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cpumask_set_cpu(cur_cpu, alloced_mask);
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break;
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}
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} else {
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cpumask_set_cpu(cur_cpu, alloced_mask);
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break;
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}
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@ -674,6 +674,11 @@ enum hv_signal_policy {
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HV_SIGNAL_POLICY_EXPLICIT,
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};
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enum hv_numa_policy {
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HV_BALANCED = 0,
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HV_LOCALIZED,
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};
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enum vmbus_device_type {
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HV_IDE = 0,
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HV_SCSI,
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@ -876,6 +881,18 @@ struct vmbus_channel {
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*/
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bool low_latency;
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/*
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* NUMA distribution policy:
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* We support teo policies:
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* 1) Balanced: Here all performance critical channels are
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* distributed evenly amongst all the NUMA nodes.
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* This policy will be the default policy.
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* 2) Localized: All channels of a given instance of a
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* performance critical service will be assigned CPUs
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* within a selected NUMA node.
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*/
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enum hv_numa_policy affinity_policy;
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};
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static inline void set_channel_lock_state(struct vmbus_channel *c, bool state)
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@ -895,6 +912,12 @@ static inline void set_channel_signal_state(struct vmbus_channel *c,
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c->signal_policy = policy;
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}
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static inline void set_channel_affinity_state(struct vmbus_channel *c,
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enum hv_numa_policy policy)
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{
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c->affinity_policy = policy;
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}
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static inline void set_channel_read_state(struct vmbus_channel *c, bool state)
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{
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c->batched_reading = state;
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