Channels/sub-channels can be affinitized to VCPUs in the guest. Implement
this affinity in a way that is NUMA aware. The current protocol distributed
the primary channels uniformly across all available CPUs. The new protocol
is NUMA aware: primary channels are distributed across the available NUMA
nodes while the sub-channels within a primary channel are distributed amongst
CPUs within the NUMA node assigned to the primary channel.
Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
---
drivers/hv/channel_mgmt.c | 72 +++++++++++++++++++++++++++------------------
include/linux/hyperv.h | 5 +++
2 files changed, 48 insertions(+), 29 deletions(-)
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index c3eba37..4506a66 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -370,25 +370,27 @@ static const struct hv_vmbus_device_id hp_devs[] = {
/*
* We use this state to statically distribute the channel interrupt load.
*/
-static u32 next_vp;
+static int next_numa_node_id;
/*
* Starting with Win8, we can statically distribute the incoming
- * channel interrupt load by binding a channel to VCPU. We
- * implement here a simple round robin scheme for distributing
- * the interrupt load.
- * We will bind channels that are not performance critical to cpu 0 and
- * performance critical channels (IDE, SCSI and Network) will be uniformly
- * distributed across all available CPUs.
+ * channel interrupt load by binding a channel to VCPU.
+ * We do this in a hierarchical fashion:
+ * First distribute the primary channels across available NUMA nodes
+ * and then distribute the subchannels amongst the CPUs in the NUMA
+ * node assigned to the primary channel.
+ *
+ * For pre-win8 hosts or non-performance critical channels we assign the
+ * first CPU in the first NUMA node.
*/
static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_guid)
{
u32 cur_cpu;
int i;
bool perf_chn = false;
- u32 max_cpus = num_online_cpus();
- struct vmbus_channel *primary = channel->primary_channel, *prev;
- unsigned long flags;
+ struct vmbus_channel *primary = channel->primary_channel;
+ int next_node;
+ struct cpumask available_mask;
for (i = IDE; i < MAX_PERF_CHN; i++) {
if (!memcmp(type_guid->b, hp_devs[i].guid,
@@ -405,36 +407,48 @@ static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_gui
* Also if the channel is not a performance critical
* channel, bind it to cpu 0.
*/
+ channel->numa_node = 0;
+ cpumask_set_cpu(0, &channel->alloced_cpus_in_node);
channel->target_cpu = 0;
channel->target_vp = hv_context.vp_index[0];
return;
}
/*
- * Primary channels are distributed evenly across all vcpus we have.
- * When the host asks us to create subchannels it usually makes us
- * num_cpus-1 offers and we are supposed to distribute the work evenly
- * among the channel itself and all its subchannels. Make sure they are
- * all assigned to different vcpus.
+ * 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.
*/
- if (!primary)
- cur_cpu = (++next_vp % max_cpus);
- else {
+ if (!primary) {
+ while (true) {
+ next_node = next_numa_node_id++;
+ if (next_node == nr_node_ids)
+ next_node = next_numa_node_id = 0;
+ if (cpumask_empty(cpumask_of_node(next_node)))
+ continue;
+ break;
+ }
+ channel->numa_node = next_node;
+ primary = channel;
+ }
+
+ if (cpumask_weight(&primary->alloced_cpus_in_node) ==
+ cpumask_weight(cpumask_of_node(primary->numa_node))) {
/*
- * Let's assign the first subchannel of a channel to the
- * primary->target_cpu+1 and all the subsequent channels to
- * the prev->target_cpu+1.
+ * We have cycled through all the CPUs in the node;
+ * reset the alloced map.
*/
- spin_lock_irqsave(&primary->lock, flags);
- if (primary->num_sc == 1)
- cur_cpu = (primary->target_cpu + 1) % max_cpus;
- else {
- prev = list_prev_entry(channel, sc_list);
- cur_cpu = (prev->target_cpu + 1) % max_cpus;
- }
- spin_unlock_irqrestore(&primary->lock, flags);
+ cpumask_clear(&primary->alloced_cpus_in_node);
}
+ cpumask_xor(&available_mask, &primary->alloced_cpus_in_node,
+ cpumask_of_node(primary->numa_node));
+
+ cur_cpu = cpumask_next(-1, &available_mask);
+ cpumask_set_cpu(cur_cpu, &primary->alloced_cpus_in_node);
+
channel->target_cpu = cur_cpu;
channel->target_vp = hv_context.vp_index[cur_cpu];
}
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 4317cd1..30d3a1f 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -697,6 +697,11 @@ struct vmbus_channel {
/* The corresponding CPUID in the guest */
u32 target_cpu;
/*
+ * State to manage the CPU affiliation of channels.
+ */
+ struct cpumask alloced_cpus_in_node;
+ int numa_node;
+ /*
* Support for sub-channels. For high performance devices,
* it will be useful to have multiple sub-channels to support
* a scalable communication infrastructure with the host.
--
1.7.4.1
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