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Commit a13e8bbe authored by K. Y. Srinivasan's avatar K. Y. Srinivasan Committed by Greg Kroah-Hartman
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Drivers: hv: vmbus: Use a round-robin algorithm for picking the outgoing channel 



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: default avatarK. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: default avatarLong Li <longli@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 96c1d058

drivers/hv/channel_mgmt.c

+15 −15
Original line number Diff line number Diff line
@@ -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 @@ int vmbus_request_offers(void) 


/*

 * 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;

include/linux/hyperv.h

+3 −0
Original line number Diff line number Diff line
@@ -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)