From 83b1bc122cab87547731a154db5feec5b9d4807c Mon Sep 17 00:00:00 2001 From: Li RongQing 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 Signed-off-by: Wang Li Signed-off-by: Li RongQing Acked-by: Jason Wang Signed-off-by: David S. Miller --- 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 835c73f..d0745dc 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); -- 2.7.4