diff options
| author | Eric Dumazet <edumazet@google.com> | 2026-01-07 10:41:59 +0000 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2026-01-13 10:12:11 +0100 |
| commit | ffe4ccd359d006eba559cb1a3c6113144b7fb38c (patch) | |
| tree | 00547b3df467260871b935d0fb3347f3c556c026 /include | |
| parent | dfdf774656205515b2d6ad94fce63c7ccbe92d91 (diff) | |
net: add net.core.qdisc_max_burst
In blamed commit, I added a check against the temporary queue
built in __dev_xmit_skb(). Idea was to drop packets early,
before any spinlock was acquired.
if (unlikely(defer_count > READ_ONCE(q->limit))) {
kfree_skb_reason(skb, SKB_DROP_REASON_QDISC_DROP);
return NET_XMIT_DROP;
}
It turned out that HTB Qdisc has a zero q->limit.
HTB limits packets on a per-class basis.
Some of our tests became flaky.
Add a new sysctl : net.core.qdisc_max_burst to control
how many packets can be stored in the temporary lockless queue.
Also add a new QDISC_BURST_DROP drop reason to better diagnose
future issues.
Thanks Neal !
Fixes: 100dfa74cad9 ("net: dev_queue_xmit() llist adoption")
Reported-and-bisected-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Link: https://patch.msgid.link/20260107104159.3669285-1-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/dropreason-core.h | 6 | ||||
| -rw-r--r-- | include/net/hotdata.h | 1 |
2 files changed, 7 insertions, 0 deletions
diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h index 58d91ccc56e0..a7b7abd66e21 100644 --- a/include/net/dropreason-core.h +++ b/include/net/dropreason-core.h @@ -67,6 +67,7 @@ FN(TC_EGRESS) \ FN(SECURITY_HOOK) \ FN(QDISC_DROP) \ + FN(QDISC_BURST_DROP) \ FN(QDISC_OVERLIMIT) \ FN(QDISC_CONGESTED) \ FN(CAKE_FLOOD) \ @@ -375,6 +376,11 @@ enum skb_drop_reason { */ SKB_DROP_REASON_QDISC_DROP, /** + * @SKB_DROP_REASON_QDISC_BURST_DROP: dropped when net.core.qdisc_max_burst + * limit is hit. + */ + SKB_DROP_REASON_QDISC_BURST_DROP, + /** * @SKB_DROP_REASON_QDISC_OVERLIMIT: dropped by qdisc when a qdisc * instance exceeds its total buffer size limit. */ diff --git a/include/net/hotdata.h b/include/net/hotdata.h index 4acec191c54a..6632b1aa7584 100644 --- a/include/net/hotdata.h +++ b/include/net/hotdata.h @@ -42,6 +42,7 @@ struct net_hotdata { int netdev_budget_usecs; int tstamp_prequeue; int max_backlog; + int qdisc_max_burst; int dev_tx_weight; int dev_rx_weight; int sysctl_max_skb_frags; |