On 2018年04月20日 19:18, Paolo Abeni wrote:
Currently, the tun driver, in absence of an eBPF steering program,
always compute the rxhash in its rx path, even when such value
is later unused due to additional checks (
This changeset moves the all the related checks just before the
__skb_get_hash_symmetric(), so that the latter is no more computed
when unneeded.
Also replace an unneeded RCU section with rcu_access_pointer().
Signed-off-by: Paolo Abeni <pab...@redhat.com>
---
drivers/net/tun.c | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 1e58be152d5c..091ace726763 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -525,11 +525,6 @@ static void tun_flow_update(struct tun_struct *tun, u32
rxhash,
rcu_read_lock();
- /* We may get a very small possibility of OOO during switching, not
- * worth to optimize.*/
- if (tun->numqueues == 1 || tfile->detached)
- goto unlock;
-
e = tun_flow_find(head, rxhash);
if (likely(e)) {
/* TODO: keep queueing to old queue until it's empty? */
@@ -548,7 +543,6 @@ static void tun_flow_update(struct tun_struct *tun, u32
rxhash,
spin_unlock_bh(&tun->lock);
}
-unlock:
rcu_read_unlock();
}
@@ -1937,10 +1931,13 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
rcu_read_unlock();
}
- rcu_read_lock();
- if (!rcu_dereference(tun->steering_prog))
+ /* Compute the costly rx hash only if needed for flow updates.
+ * We may get a very small possibility of OOO during switching, not
+ * worth to optimize.
+ */
+ if (!rcu_access_pointer(tun->steering_prog) && tun->numqueues > 1 &&
+ !tfile->detached)
rxhash = __skb_get_hash_symmetric(skb);
- rcu_read_unlock();
if (frags) {
/* Exercise flow dissector code path. */
Acked-by: Jason Wang <jasow...@redhat.com>
