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Drivers: hv: vmbus: Use a round-robin algorithm for picking the outgoing channel

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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 <kys@microsoft.com>
Reviewed-by: Long Li <longli@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
K. Y. Srinivasan 2015-02-28 11:39:02 -08:00 committed by Greg Kroah-Hartman
parent 96c1d0581d
commit a13e8bbe85
2 changed files with 18 additions and 15 deletions
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30
drivers/hv/channel_mgmt.c
View file

@ -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));
if (i == next_channel)
return cur_channel;
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;
outgoing_channel = cur_channel;
i++;
}
return outgoing_channel;

3
include/linux/hyperv.h
View file

@ -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)