git: 2da4005188ce - stable/12 - frag6: do less work in frag6_slowtimo if possible

[Mateusz Guzik]

The branch stable/12 has been updated by mjg:

URL: https://cgit.FreeBSD.org/src/commit/?id=2da4005188ced25eee5ccb803586bf31f4574fca

commit 2da4005188ced25eee5ccb803586bf31f4574fca
Author:     Mateusz Guzik <mjg at FreeBSD.org>
AuthorDate: 2021-08-13 11:32:03 +0000
Commit:     Mateusz Guzik <mjg at FreeBSD.org>
CommitDate: 2021-08-18 09:48:22 +0000

    frag6: do less work in frag6_slowtimo if possible
    
    frag6_slowtimo avoidably uses CPU on otherwise idle boxes
    
    Reviewed by:    kp
    Sponsored by:   Rubicon Communications, LLC ("Netgate")
    Differential Revision:  https://reviews.freebsd.org/D31528
    
    (cherry picked from commit 8afe9481cfa382337b8a885f358fe888bddf5982)
---
 sys/netinet6/frag6.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sys/netinet6/frag6.c b/sys/netinet6/frag6.c
index d27d21e536fe..5a31bbff9747 100644
--- a/sys/netinet6/frag6.c
+++ b/sys/netinet6/frag6.c
@@ -901,10 +901,15 @@ frag6_slowtimo(void)
 	struct ip6q *q6, *q6tmp;
 	uint32_t bucket;
 
+	if (atomic_load_int(&frag6_nfrags) == 0)
+		return;
+
 	VNET_LIST_RLOCK_NOSLEEP();
 	VNET_FOREACH(vnet_iter) {
 		CURVNET_SET(vnet_iter);
 		for (bucket = 0; bucket < IP6REASS_NHASH; bucket++) {
+			if (V_ip6qb[bucket].count == 0)
+				continue;
 			IP6QB_LOCK(bucket);
 			head = IP6QB_HEAD(bucket);
 			TAILQ_FOREACH_SAFE(q6, head, ip6q_tq, q6tmp)