Commit 83b1bc12 authored Dec 06, 2018 by Li RongQing Committed by David S. Miller Dec 06, 2018

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>

parent 7a35a50d

drivers/net/tun.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -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
		@@ -539,7 +539,9 @@ 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? */
		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 {

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