Re: [PATCH v2 net-next 08/12] inet: frags: use rhashtables for reassembly units

On 03/30/2018 03:44 PM, Kirill Tkhai wrote:

Hi, Eric,

thanks for more small patches in v2. One comment below.

quoted

-
-struct inet_frag_bucket {
-	struct hlist_head	chain;
-	spinlock_t		chain_lock;
+	struct netns_frags      *net;
+	struct rcu_head		rcu;

inet_frag_destroy() calls call_rcu() after frags are destroyed.
It looks like we may place this rcu in union with fragments and
fragments_tail and to sa

No, because I am planning to free skbs in the rcu call back very shortly.

As I mentioned, I believe we could use pure RCU lookups, without grabing a
reference and then release it after packet is processed/added to the queue.

This is not urgent, I wanted to get the first patches for review before doing
this final step, as I do not expect more than 5 % improvement from this optimization.

Also note that the ipq structure is 192 bytes, nicely using 3 cache lines.

Trying to save 16 bytes will likely reduce performance,  unless we force padding
to reach 192 bytes again :)