git: 2666f081bac0 - stable/12 - ip_reass: do less work in ipreass_slowtimo if possible

[Mateusz Guzik]

The branch stable/12 has been updated by mjg:

URL: https://cgit.FreeBSD.org/src/commit/?id=2666f081bac0c9225b7db2cb7a6776ed52bd568a

commit 2666f081bac0c9225b7db2cb7a6776ed52bd568a
Author:     Mateusz Guzik <mjg at FreeBSD.org>
AuthorDate: 2021-08-13 09:32:16 +0000
Commit:     Mateusz Guzik <mjg at FreeBSD.org>
CommitDate: 2021-08-18 09:48:16 +0000

    ip_reass: do less work in ipreass_slowtimo if possible
    
    ipreass_slowtimo avoidably uses CPU on otherwise idle boxes
    
    Reviewed by:    kp
    Sponsored by:   Rubicon Communications, LLC ("Netgate")
    Differential Revision:  https://reviews.freebsd.org/D31526
    
    (cherry picked from commit 3be3cbe06d6107486d67d8eb80480d34d084c39c)
---
 sys/netinet/ip_reass.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/sys/netinet/ip_reass.c b/sys/netinet/ip_reass.c
index 5aa75474ad60..0d5300d7382b 100644
--- a/sys/netinet/ip_reass.c
+++ b/sys/netinet/ip_reass.c
@@ -592,11 +592,16 @@ ipreass_slowtimo(void)
 {
 	struct ipq *fp, *tmp;
 
+	if (atomic_load_int(&nfrags) == 0)
+		return;
+
 	for (int i = 0; i < IPREASS_NHASH; i++) {
+		if (TAILQ_EMPTY(&V_ipq[i].head))
+			continue;
 		IPQ_LOCK(i);
 		TAILQ_FOREACH_SAFE(fp, &V_ipq[i].head, ipq_list, tmp)
 		if (--fp->ipq_ttl == 0)
-				ipq_timeout(&V_ipq[i], fp);
+			ipq_timeout(&V_ipq[i], fp);
 		IPQ_UNLOCK(i);
 	}
 }