From: Cong Wang <xiyou.wangcong@gmail.com>
To: Eric Dumazet <edumazet@google.com>
Cc: "David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Simon Horman <horms@kernel.org>,
netdev@vger.kernel.org, eric.dumazet@gmail.com,
Neal Cardwell <ncardwell@google.com>
Subject: Re: [PATCH net] net: add net.core.qdisc_max_burst
Date: Wed, 7 Jan 2026 15:25:43 -0800 [thread overview]
Message-ID: <aV7rd0dNS2NBX5b+@pop-os.localdomain> (raw)
In-Reply-To: <20260107104159.3669285-1-edumazet@google.com>
On Wed, Jan 07, 2026 at 10:41:59AM +0000, Eric Dumazet wrote:
> 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.
Hm, if q->limit is the problem here, why not introduce a new Qdisc
option for this?
>
> Add a new sysctl : net.core.qdisc_max_burst to control
> how many packets can be stored in the temporary lockless queue.
This becomes global instead of per-Qdisc. If this is intended, you might
want to document it explicitly in the documentation.
Regards,
Cong
next prev parent reply other threads:[~2026-01-07 23:25 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-07 10:41 [PATCH net] net: add net.core.qdisc_max_burst Eric Dumazet
2026-01-07 23:25 ` Cong Wang [this message]
2026-01-09 14:42 ` Eric Dumazet
2026-01-09 15:15 ` Neal Cardwell
2026-01-13 9:30 ` patchwork-bot+netdevbpf
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