[PATCH v3 21/30] net: speed up skb_rbtree_purge()

Stephen Hemminger
2018-09-13T14:58:53Z

From: Eric Dumazet <edumazet@google.com>

As measured in my prior patch ("sch_netem: faster rb tree removal"),
rbtree_postorder_for_each_entry_safe() is nice looking but much slower
than using rb_next() directly, except when tree is small enough
to fit in CPU caches (then the cost is the same)

Also note that there is not even an increase of text size :
$ size net/core/skbuff.o.before net/core/skbuff.o
text data bss dec hex filename
40711 1298 0 42009 a419 net/core/skbuff.o.before
40711 1298 0 42009 a419 net/core/skbuff.o

From: Eric Dumazet <edumazet@google.com>

Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 7c90584c66cc4b033a3b684b0e0950f79e7b7166)
---
net/core/skbuff.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 2e5eeba97de9..c7c5f05f2af1 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2850,12 +2850,15 @@ EXPORT_SYMBOL(skb_queue_purge);
*/
void skb_rbtree_purge(struct rb_root *root)
{
- struct sk_buff *skb, *next;
+ struct rb_node *p = rb_first(root);

- rbtree_postorder_for_each_entry_safe(skb, next, root, rbnode)
- kfree_skb(skb);
+ while (p) {
+ struct sk_buff *skb = rb_entry(p, struct sk_buff, rbnode);

- *root = RB_ROOT;
+ p = rb_next(p);
+ rb_erase(&skb->rbnode, root);
+ kfree_skb(skb);
+ }
}

/**
--
2.18.0