From 83b1bc122cab87547731a154db5feec5b9d4807c Mon Sep 17 00:00:00 2001
From: Li RongQing <lirongqing@baidu.com>
Date: Thu, 6 Dec 2018 16:08:17 +0800
Subject: [PATCH] tun: align write-heavy flow entry members to a cache line
tun flow entry 'updated' fields are written when receive
every packet. Thus if a flow is receiving packets from a
particular flow entry, it'll cause false-sharing with
all the other who has looked it up, so move it in its own
cache line
and update 'queue_index' and 'update' field only when
they are changed to reduce the cache false-sharing.
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
Signed-off-by: Wang Li <wangli39@baidu.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
drivers/net/tun.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 835c73f42ae7a..d0745dc819769 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -201,7 +201,7 @@ struct tun_flow_entry {
u32 rxhash;
u32 rps_rxhash;
int queue_index;
- unsigned long updated;
+ unsigned long updated ____cacheline_aligned_in_smp;
};
#define TUN_NUM_FLOW_ENTRIES 1024
@@ -539,8 +539,10 @@ static void tun_flow_update(struct tun_struct *tun, u32 rxhash,
e = tun_flow_find(head, rxhash);
if (likely(e)) {
/* TODO: keep queueing to old queue until it's empty? */
- e->queue_index = queue_index;
- e->updated = jiffies;
+ if (e->queue_index != queue_index)
+ e->queue_index = queue_index;
+ if (e->updated != jiffies)
+ e->updated = jiffies;
sock_rps_record_flow_hash(e->rps_rxhash);
} else {
spin_lock_bh(&tun->lock);
--
2.30.2