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Date: Tue, 14 Nov 2017 20:56:04 -0500 From: Willem de Bruijn <willemdebruijn.kernel@...il.com> To: John Fastabend <john.fastabend@...il.com> Cc: Daniel Borkmann <daniel@...earbox.net>, Eric Dumazet <eric.dumazet@...il.com>, make0818@...il.com, Network Development <netdev@...r.kernel.org>, Jiří Pírko <jiri@...nulli.us>, Cong Wang <xiyou.wangcong@...il.com> Subject: Re: [RFC PATCH 03/17] net: sched: remove remaining uses for qdisc_qlen in xmit path On Tue, Nov 14, 2017 at 7:11 PM, Willem de Bruijn <willemdebruijn.kernel@...il.com> wrote: > On Mon, Nov 13, 2017 at 3:08 PM, John Fastabend > <john.fastabend@...il.com> wrote: >> sch_direct_xmit() uses qdisc_qlen as a return value but all call sites >> of the routine only check if it is zero or not. Simplify the logic so >> that we don't need to return an actual queue length value. >> >> This introduces a case now where sch_direct_xmit would have returned >> a qlen of zero but now it returns true. > > You mean the first case, when the likely(skb) branch failed? > Can that return false, then? I misunderstood. __qdisc_run will just take one extra loop, since it will no longer break out of the loop on reading the last packet on the queue with qdisc_restart. That does have a subtle (but benign if rare) side effect of possibly calling __netif_schedule while there is nothing queued, if either the quota is exactly exhausted or need_resched is true.
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