This is a note to let you know that I've just added the patch titled
vmbus: more host signalling avoidance
to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
vmbus-more-host-signalling-avoidance.patch
and it can be found in the queue-4.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 03bad714a1619c0074eb44d6f217c505fe27030f Mon Sep 17 00:00:00 2001
From: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
Date: Sun, 25 Jun 2017 12:30:28 -0700
Subject: vmbus: more host signalling avoidance
From: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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);
Patches currently in stable-queue which might be from stephen@xxxxxxxxxxxxxxxxxx are
queue-4.13/vmbus-more-host-signalling-avoidance.patch
queue-4.13/vmbus-refactor-hv_signal_on_read.patch
queue-4.13/vmbus-simplify-hv_ringbuffer_read.patch
queue-4.13/vmbus-eliminate-duplicate-cached-index.patch