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Drivers: hv: vmbus: Implement APIs to support "in place" consumption of vmbus packets

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Implement APIs for in-place consumption of vmbus packets. Currently, each
packet is copied and processed one at a time and as part of processing
each packet we potentially may signal the host (if it is waiting for
room to produce a packet).

These APIs help batched in-place processing of vmbus packets.
We also optimize host signaling by having a separate API to signal
the end of in-place consumption. With netvsc using these APIs,
on an iperf run on average I see about 20X reduction in checks to
signal the host.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
K. Y. Srinivasan 2016-04-02 17:59:51 -07:00 committed by Greg Kroah-Hartman
parent 687f32e6d9
commit ab028db41c
2 changed files with 87 additions and 0 deletions
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1
drivers/hv/ring_buffer.c
View File

@ -132,6 +132,7 @@ hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
u32 next_read_location)
{
ring_info->ring_buffer->read_index = next_read_location;
ring_info->priv_read_index = next_read_location;
}
/* Get the size of the ring buffer. */

86
include/linux/hyperv.h
View File

@ -126,6 +126,8 @@ struct hv_ring_buffer_info {
u32 ring_datasize; /* < ring_size */
u32 ring_data_startoffset;
u32 priv_write_index;
u32 priv_read_index;
};
/*
@ -1420,4 +1422,88 @@ static inline bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi)
return false;
}
/*
* An API to support in-place processing of incoming VMBUS packets.
*/
#define VMBUS_PKT_TRAILER 8
static inline struct vmpacket_descriptor *
get_next_pkt_raw(struct vmbus_channel *channel)
{
struct hv_ring_buffer_info *ring_info = &channel->inbound;
u32 read_loc = ring_info->priv_read_index;
void *ring_buffer = hv_get_ring_buffer(ring_info);
struct vmpacket_descriptor *cur_desc;
u32 packetlen;
u32 dsize = ring_info->ring_datasize;
u32 delta = read_loc - ring_info->ring_buffer->read_index;
u32 bytes_avail_toread = (hv_get_bytes_to_read(ring_info) - delta);
if (bytes_avail_toread < sizeof(struct vmpacket_descriptor))
return NULL;
if ((read_loc + sizeof(*cur_desc)) > dsize)
return NULL;
cur_desc = ring_buffer + read_loc;
packetlen = cur_desc->len8 << 3;
/*
* If the packet under consideration is wrapping around,
* return failure.
*/
if ((read_loc + packetlen + VMBUS_PKT_TRAILER) > (dsize - 1))
return NULL;
return cur_desc;
}
/*
* A helper function to step through packets "in-place"
* This API is to be called after each successful call
* get_next_pkt_raw().
*/
static inline void put_pkt_raw(struct vmbus_channel *channel,
struct vmpacket_descriptor *desc)
{
struct hv_ring_buffer_info *ring_info = &channel->inbound;
u32 read_loc = ring_info->priv_read_index;
u32 packetlen = desc->len8 << 3;
u32 dsize = ring_info->ring_datasize;
if ((read_loc + packetlen + VMBUS_PKT_TRAILER) > dsize)
BUG();
/*
* Include the packet trailer.
*/
ring_info->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
}
/*
* This call commits the read index and potentially signals the host.
* Here is the pattern for using the "in-place" consumption APIs:
*
* while (get_next_pkt_raw() {
* process the packet "in-place";
* put_pkt_raw();
* }
* if (packets processed in place)
* commit_rd_index();
*/
static inline void commit_rd_index(struct vmbus_channel *channel)
{
struct hv_ring_buffer_info *ring_info = &channel->inbound;
/*
* Make sure all reads are done before we update the read index since
* the writer may start writing to the read area once the read index
* is updated.
*/
virt_rmb();
ring_info->ring_buffer->read_index = ring_info->priv_read_index;
if (hv_need_to_signal_on_read(ring_info))
vmbus_set_event(channel);
}
#endif /* _HYPERV_H */