[PATCH 01/28] Drivers: hv: Implement routines for read side signaling optimization

K. Y. Srinivasan
2012-12-01T14:23:43Z

Implement functions that will support read-side signaling optimization.
By having the reader indicate the start of the "read" operation and the
"end" of the read operation we can more efficiently handle the signaling
protocol: while the read is in progress, there is no need for the "writer"
to signal the "reader" as new items are put on the read queue.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
---
drivers/hv/hyperv_vmbus.h | 4 ++++
drivers/hv/ring_buffer.c | 24 ++++++++++++++++++++++++
2 files changed, 28 insertions(+), 0 deletions(-)

diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index d8d1fad..3184f6f 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -570,6 +570,10 @@ u32 hv_get_ringbuffer_interrupt_mask(struct hv_ring_buffer_info *ring_info);
void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
struct hv_ring_buffer_debug_info *debug_info);

+void hv_begin_read(struct hv_ring_buffer_info *rbi);
+
+u32 hv_end_read(struct hv_ring_buffer_info *rbi);
+
/*
* Maximum channels is determined by the size of the interrupt page
* which is PAGE_SIZE. 1/2 of PAGE_SIZE is for send endpoint interrupt
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 7233c88..0010792 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -29,6 +29,30 @@

#include "hyperv_vmbus.h"

+void hv_begin_read(struct hv_ring_buffer_info *rbi)
+{
+ rbi->ring_buffer->interrupt_mask = 1;
+ smp_mb();
+}
+
+u32 hv_end_read(struct hv_ring_buffer_info *rbi)
+{
+ u32 read;
+ u32 write;
+
+ rbi->ring_buffer->interrupt_mask = 0;
+ smp_mb();
+
+ /*
+ * Now check to see if the ring buffer is still empty.
+ * If it is not, we raced and we need to process new
+ * incoming messages.
+ */
+ hv_get_ringbuffer_availbytes(rbi, &read, &write);
+
+ return read;
+}
+

/*
* hv_get_next_write_location()
--
1.7.4.1