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authorK. Y. Srinivasan <kys@microsoft.com>2012-12-01 06:46:35 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-01-17 10:46:39 -0800
commitf878f3d59ed26f489add852ed6d5c8e5f3bbb1aa (patch)
treea43fb3ee6c95abb34660921dad31b80a59d9cde6 /drivers/hv
parent7ae3e035195735f9b6ce3308b6240af877a41ea0 (diff)
Drivers: hv: Optimize signaling in the read path
Now that we have the infratructure for correctly determining when we should signal the host; optimize the signaling on the read side - signaling the guest from the host. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/hv')
-rw-r--r--drivers/hv/connection.c28
1 files changed, 25 insertions, 3 deletions
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 650c9f0b6642..d1019a770ad7 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -212,6 +212,9 @@ static void process_chn_event(u32 relid)
{
struct vmbus_channel *channel;
unsigned long flags;
+ void *arg;
+ bool read_state;
+ u32 bytes_to_read;
/*
* Find the channel based on this relid and invokes the
@@ -234,10 +237,29 @@ static void process_chn_event(u32 relid)
*/
spin_lock_irqsave(&channel->inbound_lock, flags);
- if (channel->onchannel_callback != NULL)
- channel->onchannel_callback(channel->channel_callback_context);
- else
+ if (channel->onchannel_callback != NULL) {
+ arg = channel->channel_callback_context;
+ read_state = channel->batched_reading;
+ /*
+ * This callback reads the messages sent by the host.
+ * We can optimize host to guest signaling by ensuring:
+ * 1. While reading the channel, we disable interrupts from
+ * host.
+ * 2. Ensure that we process all posted messages from the host
+ * before returning from this callback.
+ * 3. Once we return, enable signaling from the host. Once this
+ * state is set we check to see if additional packets are
+ * available to read. In this case we repeat the process.
+ */
+
+ do {
+ hv_begin_read(&channel->inbound);
+ channel->onchannel_callback(arg);
+ bytes_to_read = hv_end_read(&channel->inbound);
+ } while (read_state && (bytes_to_read != 0));
+ } else {
pr_err("no channel callback for relid - %u\n", relid);
+ }
spin_unlock_irqrestore(&channel->inbound_lock, flags);
}

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