lkml.org 
[lkml]   [2017]   [Oct]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.13 11/11] vmbus: more host signalling avoidance
Date
4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stephen Hemminger <stephen@networkplumber.org>

commit 03bad714a1619c0074eb44d6f217c505fe27030f upstream.

Don't signal host if it has disabled interrupts for that
ring buffer. Check the feature bit to see if host supports
pending send size flag.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/hv/ring_buffer.c | 27 +++++++++++++++++++--------
1 file changed, 19 insertions(+), 8 deletions(-)

--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -396,7 +396,6 @@ void hv_pkt_iter_close(struct vmbus_chan
{
struct hv_ring_buffer_info *rbi = &channel->inbound;
u32 orig_write_sz = hv_get_bytes_to_write(rbi);
- u32 pending_sz;

/*
* Make sure all reads are done before we update the read index since
@@ -419,15 +418,27 @@ void hv_pkt_iter_close(struct vmbus_chan
*/
virt_mb();

- pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
- /* If the other end is not blocked on write don't bother. */
- if (pending_sz == 0)
+ /* If host has disabled notifications then skip */
+ if (rbi->ring_buffer->interrupt_mask)
return;

- if (hv_get_bytes_to_write(rbi) < pending_sz)
- return;
+ if (rbi->ring_buffer->feature_bits.feat_pending_send_sz) {
+ u32 pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
+
+ /*
+ * If there was space before we began iteration,
+ * then host was not blocked. Also handles case where
+ * pending_sz is zero then host has nothing pending
+ * and does not need to be signaled.
+ */
+ if (orig_write_sz > pending_sz)
+ return;
+
+ /* If pending write will not fit, don't give false hope. */
+ if (hv_get_bytes_to_write(rbi) < pending_sz)
+ return;
+ }

- if (orig_write_sz < pending_sz)
- vmbus_setevent(channel);
+ vmbus_setevent(channel);
}
EXPORT_SYMBOL_GPL(hv_pkt_iter_close);

\
 
 \ /
  Last update: 2017-10-22 17:24    [W:0.071 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site