INTRO (9) NetBSD Kernel Developer's Manual INTRO (9) NAME ...

ALTQ (9) NetBSD Kernel Developer’s Manual ALTQ (9)if (something_goes_wrong) { | if (something_goes_wrong) {IF_PREPEND(&ifp->if_snd, m); |return; | return;} | }|| /∗ at this point, the driver| ∗ is committed to send this| ∗ packet.| ∗/| IFQ_DEQUEUE(&ifp->if_snd, m);|/∗ kick the hardware ∗/ | /∗ kick the hardware ∗/} | }|Purge operationUse IFQ_PURGE() to empty the queue. Note that a non-work conserving queue cannot be emptied by adequeue loop.##old-style##|while (ifp->if_snd.ifq_head != NULL) {|IF_DEQUEUE(&ifp->if_snd, m); |m_freem(m); |} ||##new-style##IFQ_PURGE(&ifp->if_snd);Attach routineUse IFQ_SET_MAXLEN() to set ifq_maxlen to len. Add IFQ_SET_READY() to show this driver isconverted to the new style. (This is used to distinguish new-style drivers.)##old-style##ifp->if_snd.ifq_maxlen = qsize;if_attach(ifp);Other issuesThe new macros for statistics:##new-style##|| IFQ_SET_MAXLEN(&ifp->if_snd, qsize);| IFQ_SET_READY(&ifp->if_snd);| if_attach(ifp);|##old-style####new-style##|IF_DROP(&ifp->if_snd);| IFQ_INC_DROPS(&ifp->if_snd);|ifp->if_snd.ifq_len++;| IFQ_INC_LEN(&ifp->if_snd);|ifp->if_snd.ifq_len--;| IFQ_DEC_LEN(&ifp->if_snd);|Some drivers instruct the hardware to invoke transmission complete interrupts only when it thinks necessary.Rate-limiting breaks its assumption.NetBSD 3.0 October 12, 2006 6