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Drivers: hv: Implement flow management on the send side

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Implement flow management on the send side. When the sender is blocked, the reader
can potentially signal the sender to indicate there is now room to send.

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>
This commit is contained in:
K. Y. Srinivasan 2012-12-01 06:46:57 -08:00 committed by Greg Kroah-Hartman
parent 2a5c43a821
commit c2b8e5202c
3 changed files with 61 additions and 4 deletions
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12
drivers/hv/channel.c
View file

@ -735,6 +735,7 @@ int vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
u32 packetlen;
u32 userlen;
int ret;
bool signal = false;
*buffer_actual_len = 0;
*requestid = 0;
@ -761,8 +762,10 @@ int vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
/* Copy over the packet to the user buffer */
ret = hv_ringbuffer_read(&channel->inbound, buffer, userlen,
(desc.offset8 << 3));
(desc.offset8 << 3), &signal);
if (signal)
vmbus_setevent(channel);
return 0;
}
@ -779,6 +782,7 @@ int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer,
u32 packetlen;
u32 userlen;
int ret;
bool signal = false;
*buffer_actual_len = 0;
*requestid = 0;
@ -805,7 +809,11 @@ int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer,
*requestid = desc.trans_id;
/* Copy over the entire packet to the user buffer */
ret = hv_ringbuffer_read(&channel->inbound, buffer, packetlen, 0);
ret = hv_ringbuffer_read(&channel->inbound, buffer, packetlen, 0,
&signal);
if (signal)
vmbus_setevent(channel);
return 0;
}

2
drivers/hv/hyperv_vmbus.h
View file

@ -550,7 +550,7 @@ int hv_ringbuffer_peek(struct hv_ring_buffer_info *ring_info, void *buffer,
int hv_ringbuffer_read(struct hv_ring_buffer_info *ring_info,
void *buffer,
u32 buflen,
u32 offset);
u32 offset, bool *signal);
void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,

51
drivers/hv/ring_buffer.c
View file

@ -84,6 +84,50 @@ static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
return false;
}
/*
* To optimize the flow management on the send-side,
* when the sender is blocked because of lack of
* sufficient space in the ring buffer, potential the
* consumer of the ring buffer can signal the producer.
* This is controlled by the following parameters:
*
* 1. pending_send_sz: This is the size in bytes that the
* producer is trying to send.
* 2. The feature bit feat_pending_send_sz set to indicate if
* the consumer of the ring will signal when the ring
* state transitions from being full to a state where
* there is room for the producer to send the pending packet.
*/
static bool hv_need_to_signal_on_read(u32 old_rd,
struct hv_ring_buffer_info *rbi)
{
u32 prev_write_sz;
u32 cur_write_sz;
u32 r_size;
u32 write_loc = rbi->ring_buffer->write_index;
u32 read_loc = rbi->ring_buffer->read_index;
u32 pending_sz = rbi->ring_buffer->pending_send_sz;
/*
* If the other end is not blocked on write don't bother.
*/
if (pending_sz == 0)
return false;
r_size = rbi->ring_datasize;
cur_write_sz = write_loc >= read_loc ? r_size - (write_loc - read_loc) :
read_loc - write_loc;
prev_write_sz = write_loc >= old_rd ? r_size - (write_loc - old_rd) :
old_rd - write_loc;
if ((prev_write_sz < pending_sz) && (cur_write_sz >= pending_sz))
return true;
return false;
}
/*
* hv_get_next_write_location()
@ -461,13 +505,14 @@ int hv_ringbuffer_peek(struct hv_ring_buffer_info *Inring_info,
*
*/
int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
u32 buflen, u32 offset)
u32 buflen, u32 offset, bool *signal)
{
u32 bytes_avail_towrite;
u32 bytes_avail_toread;
u32 next_read_location = 0;
u64 prev_indices = 0;
unsigned long flags;
u32 old_read;
if (buflen <= 0)
return -EINVAL;
@ -478,6 +523,8 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
&bytes_avail_toread,
&bytes_avail_towrite);
old_read = bytes_avail_toread;
/* Make sure there is something to read */
if (bytes_avail_toread < buflen) {
spin_unlock_irqrestore(&inring_info->ring_lock, flags);
@ -508,5 +555,7 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
spin_unlock_irqrestore(&inring_info->ring_lock, flags);
*signal = hv_need_to_signal_on_read(old_read, inring_info);
return 0;
}