[PATCH net-next 06/15] netvsc: prefetch the first incoming ring element

[Stephen Hemminger]

In interrupt handler, prefetch the first incoming ring element
so that it is in cache by the time NAPI poll gets to it.

Signed-off-by: Stephen Hemminger <sthem...@microsoft.com>
---
 drivers/net/hyperv/netvsc.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index ee5f8c520977..cee8e020ac56 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -29,6 +29,8 @@
 #include <linux/netdevice.h>
 #include <linux/if_ether.h>
 #include <linux/vmalloc.h>
+#include <linux/prefetch.h>
+
 #include <asm/sync_bitops.h>
 
 #include "hyperv_net.h"
@@ -1280,10 +1282,15 @@ int netvsc_poll(struct napi_struct *napi, int budget)
 void netvsc_channel_cb(void *context)
 {
        struct netvsc_channel *nvchan = context;
+       struct vmbus_channel *channel = nvchan->channel;
+       struct hv_ring_buffer_info *rbi = &channel->inbound;
+
+       /* preload first vmpacket descriptor */
+       prefetch(hv_get_ring_buffer(rbi) + rbi->priv_read_index);
 
        if (napi_schedule_prep(&nvchan->napi)) {
                /* disable interupts from host */
-               hv_begin_read(&nvchan->channel->inbound);
+               hv_begin_read(rbi);
 
                __napi_schedule(&nvchan->napi);
        }
-- 
2.11.0