The current algorithm for picking an outgoing channel was not distributing
the load well. Implement a simple round-robin scheme to ensure good
distribution of the outgoing traffic.
Signed-off-by: K. Y. Srinivasan <k...@microsoft.com>
Reviewed-by: Long Li <lon...@microsoft.com>
---
drivers/hv/channel_mgmt.c | 30 +++++++++++++++---------------
include/linux/hyperv.h | 3 +++
2 files changed, 18 insertions(+), 15 deletions(-)
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index b1e5a5f..6117891 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -350,6 +350,7 @@ static void vmbus_process_offer(struct vmbus_channel
*newchannel)
}
newchannel->state = CHANNEL_OPEN_STATE;
+ channel->num_sc++;
if (channel->sc_creation_callback != NULL)
/*
* We need to invoke the sub-channel creation
@@ -862,9 +863,8 @@ cleanup:
/*
* Retrieve the (sub) channel on which to send an outgoing request.
- * When a primary channel has multiple sub-channels, we choose a
- * channel whose VCPU binding is closest to the VCPU on which
- * this call is being made.
+ * When a primary channel has multiple sub-channels, we try to
+ * distribute the load equally amongst all available channels.
*/
struct vmbus_channel *vmbus_get_outgoing_channel(struct vmbus_channel *primary)
{
@@ -872,11 +872,19 @@ struct vmbus_channel *vmbus_get_outgoing_channel(struct
vmbus_channel *primary)
int cur_cpu;
struct vmbus_channel *cur_channel;
struct vmbus_channel *outgoing_channel = primary;
- int cpu_distance, new_cpu_distance;
+ int next_channel;
+ int i = 1;
if (list_empty(&primary->sc_list))
return outgoing_channel;
+ next_channel = primary->next_oc++;
+
+ if (next_channel > (primary->num_sc)) {
+ primary->next_oc = 0;
+ return outgoing_channel;
+ }
+
cur_cpu = hv_context.vp_index[get_cpu()];
put_cpu();
list_for_each_safe(cur, tmp, &primary->sc_list) {
@@ -887,18 +895,10 @@ struct vmbus_channel *vmbus_get_outgoing_channel(struct
vmbus_channel *primary)
if (cur_channel->target_vp == cur_cpu)
return cur_channel;
- cpu_distance = ((outgoing_channel->target_vp > cur_cpu) ?
- (outgoing_channel->target_vp - cur_cpu) :
- (cur_cpu - outgoing_channel->target_vp));
-
- new_cpu_distance = ((cur_channel->target_vp > cur_cpu) ?
- (cur_channel->target_vp - cur_cpu) :
- (cur_cpu - cur_channel->target_vp));
-
- if (cpu_distance < new_cpu_distance)
- continue;
+ if (i == next_channel)
+ return cur_channel;
- outgoing_channel = cur_channel;
+ i++;
}
return outgoing_channel;
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index dd92a85..1ca5824 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -761,6 +761,9 @@ struct vmbus_channel {
* link up channels based on their CPU affinity.
*/
struct list_head percpu_list;
+
+ int num_sc;
+ int next_oc;
};
static inline void set_channel_read_state(struct vmbus_channel *c, bool state)
--
1.7.4.1
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