From: stephen hemminger <stephen@networkplumber.org>
Date: Mon, 24 Jul 2017 10:57:27 -0700
Patch-mainline: v4.14-rc1
Subject: netvsc: prefetch the first incoming ring element
Git-commit: 43bf99ce009de710b68473480a611f3b5ddd11d5
References: fate#323887
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 <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Olaf Hering <ohering@suse.de>
---
drivers/net/hyperv/netvsc.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -30,6 +30,7 @@
#include <linux/if_ether.h>
#include <linux/vmalloc.h>
#include <linux/rtnetlink.h>
+#include <linux/prefetch.h>
#include <asm/sync_bitops.h>
@@ -1265,10 +1266,15 @@ 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);
}