net_sched: use qdisc_skb_cb(skb)->pkt_segs in bstats_update()

Avoid up to two cache line misses in qdisc dequeue() to fetch
skb_shinfo(skb)->gso_segs/gso_size while qdisc spinlock is held.

This gives a 5 % improvement in a TX intensive workload.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20251121083256.674562-6-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 9cd8b5d..cdf7a58 100644 (file)
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -829,6 +829,15 @@ static inline unsigned int qdisc_pkt_len(const struct sk_buff *skb)
        return qdisc_skb_cb(skb)->pkt_len;
 }
 
+static inline unsigned int qdisc_pkt_segs(const struct sk_buff *skb)
+{
+       u32 pkt_segs = qdisc_skb_cb(skb)->pkt_segs;
+
+       DEBUG_NET_WARN_ON_ONCE(pkt_segs !=
+                       (skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 1));
+       return pkt_segs;
+}
+
 /* additional qdisc xmit flags (NET_XMIT_MASK in linux/netdevice.h) */
 enum net_xmit_qdisc_t {
        __NET_XMIT_STOLEN = 0x00010000,
@@ -870,9 +879,7 @@ static inline void _bstats_update(struct gnet_stats_basic_sync *bstats,
 static inline void bstats_update(struct gnet_stats_basic_sync *bstats,
                                 const struct sk_buff *skb)
 {
-       _bstats_update(bstats,
-                      qdisc_pkt_len(skb),
-                      skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 1);
+       _bstats_update(bstats, qdisc_pkt_len(skb), qdisc_pkt_segs(skb));
 }
 
 static inline void qdisc_bstats_cpu_update(struct Qdisc *sch,

diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c
index 9213129..a208800 100644 (file)
--- a/net/sched/sch_cake.c
+++ b/net/sched/sch_cake.c
@@ -1800,6 +1800,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                skb_list_walk_safe(segs, segs, nskb) {
                        skb_mark_not_on_list(segs);
                        qdisc_skb_cb(segs)->pkt_len = segs->len;
+                       qdisc_skb_cb(segs)->pkt_segs = 1;
                        cobalt_set_enqueue_time(segs, now);
                        get_cobalt_cb(segs)->adjusted_len = cake_overhead(q,
                                                                          segs);

diff --git a/net/sched/sch_dualpi2.c b/net/sched/sch_dualpi2.c
index 4b975fe..6d7e638 100644 (file)
--- a/net/sched/sch_dualpi2.c
+++ b/net/sched/sch_dualpi2.c
@@ -475,6 +475,7 @@ static int dualpi2_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                         * (3) Enqueue fragment & set ts in dualpi2_enqueue_skb
                         */
                        qdisc_skb_cb(nskb)->pkt_len = nskb->len;
+                       qdisc_skb_cb(nskb)->pkt_segs = 1;
                        dualpi2_skb_cb(nskb)->classified =
                                dualpi2_skb_cb(skb)->classified;
                        dualpi2_skb_cb(nskb)->ect = dualpi2_skb_cb(skb)->ect;

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index eafc316..32a5f33 100644 (file)
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -429,6 +429,7 @@ static struct sk_buff *netem_segment(struct sk_buff *skb, struct Qdisc *sch,
        struct sk_buff *segs;
        netdev_features_t features = netif_skb_features(skb);
 
+       qdisc_skb_cb(skb)->pkt_segs = 1;
        segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
 
        if (IS_ERR_OR_NULL(segs)) {

diff --git a/net/sched/sch_qfq.c b/net/sched/sch_qfq.c
index 2255355..d920f57 100644 (file)
--- a/net/sched/sch_qfq.c
+++ b/net/sched/sch_qfq.c
@@ -1250,7 +1250,7 @@ static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                }
        }
 
-       gso_segs = skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 1;
+       gso_segs = qdisc_pkt_segs(skb);
        err = qdisc_enqueue(skb, cl->qdisc, to_free);
        if (unlikely(err != NET_XMIT_SUCCESS)) {
                pr_debug("qfq_enqueue: enqueue failed %d\n", err);

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 39b7353..300d577 100644 (file)
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -595,6 +595,7 @@ static int taprio_enqueue_segmented(struct sk_buff *skb, struct Qdisc *sch,
        skb_list_walk_safe(segs, segs, nskb) {
                skb_mark_not_on_list(segs);
                qdisc_skb_cb(segs)->pkt_len = segs->len;
+               qdisc_skb_cb(segs)->pkt_segs = 1;
                slen += segs->len;
 
                /* FIXME: we should be segmenting to a smaller size

diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
index 4c977f0..f234016 100644 (file)
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -221,6 +221,7 @@ static int tbf_segment(struct sk_buff *skb, struct Qdisc *sch,
                skb_mark_not_on_list(segs);
                seg_len = segs->len;
                qdisc_skb_cb(segs)->pkt_len = seg_len;
+               qdisc_skb_cb(segs)->pkt_segs = 1;
                ret = qdisc_enqueue(segs, q->qdisc, to_free);
                if (ret != NET_XMIT_SUCCESS) {
                        if (net_xmit_drop_count(ret))