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Commit 98fa8cf4 authored by K. Y. Srinivasan's avatar K. Y. Srinivasan Committed by Greg Kroah-Hartman
Browse files

Drivers: hv: Optimize the signaling on the write path 



The host has already implemented the "read" side optimizations.
Leverage that to optimize "write" side signaling.

Signed-off-by: default avatarK. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: default avatarHaiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f878f3d5

drivers/hv/channel.c

+9 −6
Original line number Diff line number Diff line
@@ -564,6 +564,7 @@ int vmbus_sendpacket(struct vmbus_channel *channel, const void *buffer, 
	struct scatterlist bufferlist[3];

	u64 aligned_data = 0;

	int ret;

	bool signal = false;





	/* Setup the descriptor */
@@ -580,9 +581,9 @@ int vmbus_sendpacket(struct vmbus_channel *channel, const void *buffer, 
	sg_set_buf(&bufferlist[2], &aligned_data,

		   packetlen_aligned - packetlen);



	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3);

	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);



	if (ret == 0 && !hv_get_ringbuffer_interrupt_mask(&channel->outbound))

	if (ret == 0 && signal)

		vmbus_setevent(channel);



	return ret;
@@ -606,6 +607,7 @@ int vmbus_sendpacket_pagebuffer(struct vmbus_channel *channel, 
	u32 packetlen_aligned;

	struct scatterlist bufferlist[3];

	u64 aligned_data = 0;

	bool signal = false;



	if (pagecount > MAX_PAGE_BUFFER_COUNT)

		return -EINVAL;
@@ -641,9 +643,9 @@ int vmbus_sendpacket_pagebuffer(struct vmbus_channel *channel, 
	sg_set_buf(&bufferlist[2], &aligned_data,

		packetlen_aligned - packetlen);



	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3);

	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);



	if (ret == 0 && !hv_get_ringbuffer_interrupt_mask(&channel->outbound))

	if (ret == 0 && signal)

		vmbus_setevent(channel);



	return ret;
@@ -665,6 +667,7 @@ int vmbus_sendpacket_multipagebuffer(struct vmbus_channel *channel, 
	u32 packetlen_aligned;

	struct scatterlist bufferlist[3];

	u64 aligned_data = 0;

	bool signal = false;

	u32 pfncount = NUM_PAGES_SPANNED(multi_pagebuffer->offset,

					 multi_pagebuffer->len);
@@ -703,9 +706,9 @@ int vmbus_sendpacket_multipagebuffer(struct vmbus_channel *channel, 
	sg_set_buf(&bufferlist[2], &aligned_data,

		packetlen_aligned - packetlen);



	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3);

	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);



	if (ret == 0 && !hv_get_ringbuffer_interrupt_mask(&channel->outbound))

	if (ret == 0 && signal)

		vmbus_setevent(channel);



	return ret;

drivers/hv/hyperv_vmbus.h

+1 −1
Original line number Diff line number Diff line
@@ -555,7 +555,7 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info); 


int hv_ringbuffer_write(struct hv_ring_buffer_info *ring_info,

		    struct scatterlist *sglist,

		    u32 sgcount);

		    u32 sgcount, bool *signal);



int hv_ringbuffer_peek(struct hv_ring_buffer_info *ring_info, void *buffer,

		   u32 buflen);

drivers/hv/ring_buffer.c

+39 −3
Original line number Diff line number Diff line
@@ -53,6 +53,37 @@ u32 hv_end_read(struct hv_ring_buffer_info *rbi) 
	return read;

}



/*

 * When we write to the ring buffer, check if the host needs to

 * be signaled. Here is the details of this protocol:

 *

 *	1. The host guarantees that while it is draining the

 *	   ring buffer, it will set the interrupt_mask to

 *	   indicate it does not need to be interrupted when

 *	   new data is placed.

 *

 *	2. The host guarantees that it will completely drain

 *	   the ring buffer before exiting the read loop. Further,

 *	   once the ring buffer is empty, it will clear the

 *	   interrupt_mask and re-check to see if new data has

 *	   arrived.

 */



static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)

{

	if (rbi->ring_buffer->interrupt_mask)

		return false;



	/*

	 * This is the only case we need to signal when the

	 * ring transitions from being empty to non-empty.

	 */

	if (old_write == rbi->ring_buffer->read_index)

		return true;



	return false;

}





/*

 * hv_get_next_write_location()
@@ -322,7 +353,7 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info) 
 *

 */

int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,

		    struct scatterlist *sglist, u32 sgcount)

		    struct scatterlist *sglist, u32 sgcount, bool *signal)

{

	int i = 0;

	u32 bytes_avail_towrite;
@@ -331,6 +362,7 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, 


	struct scatterlist *sg;

	u32 next_write_location;

	u32 old_write;

	u64 prev_indices = 0;

	unsigned long flags;
@@ -359,6 +391,8 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, 
	/* Write to the ring buffer */

	next_write_location = hv_get_next_write_location(outring_info);



	old_write = next_write_location;



	for_each_sg(sglist, sg, sgcount, i)

	{

		next_write_location = hv_copyto_ringbuffer(outring_info,
@@ -375,14 +409,16 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, 
					     &prev_indices,

					     sizeof(u64));



	/* Make sure we flush all writes before updating the writeIndex */

	smp_wmb();

	/* Issue a full memory barrier before updating the write index */

	smp_mb();



	/* Now, update the write location */

	hv_set_next_write_location(outring_info, next_write_location);





	spin_unlock_irqrestore(&outring_info->ring_lock, flags);



	*signal = hv_need_to_signal(old_write, outring_info);

	return 0;

}