ifpoll: Reorganize TX/RX polling sysctl tree

[dragonfly.git] / sys / net / if_poll.c

/*-
 * Copyright (c) 2001-2002 Luigi Rizzo
 *
 * Supported by: the Xorp Project (www.xorp.org)
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD: src/sys/kern/kern_poll.c,v 1.2.2.4 2002/06/27 23:26:33 luigi Exp $
 */

#include "opt_ifpoll.h"

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/malloc.h>
#include <sys/serialize.h>
#include <sys/socket.h>
#include <sys/sysctl.h>

#include <sys/thread2.h>
#include <sys/msgport2.h>

#include <machine/atomic.h>
#include <machine/clock.h>
#include <machine/smp.h>

#include <net/if.h>
#include <net/if_poll.h>
#include <net/netmsg2.h>

/*
 * Polling support for network device drivers.
 *
 * Drivers which support this feature try to register one status polling
 * handler and several TX/RX polling handlers with the polling code.
 * If interface's if_qpoll is called with non-NULL second argument, then
 * a register operation is requested, else a deregister operation is
 * requested.  If the requested operation is "register", driver should
 * setup the ifpoll_info passed in accoding its own needs:
 *   ifpoll_info.ifpi_status.status_func == NULL
 *     No status polling handler will be installed on CPU(0)
 *   ifpoll_info.ifpi_rx[n].poll_func == NULL
 *     No RX polling handler will be installed on CPU(n)
 *   ifpoll_info.ifpi_tx[n].poll_func == NULL
 *     No TX polling handler will be installed on CPU(n)
 *
 * All of the registered polling handlers are called only if the interface
 * is marked as 'IFF_RUNNING and IFF_NPOLLING'.  However, the interface's
 * register and deregister function (ifnet.if_qpoll) will be called even
 * if interface is not marked with 'IFF_RUNNING'.
 *
 * If registration is successful, the driver must disable interrupts,
 * and further I/O is performed through the TX/RX polling handler, which
 * are invoked (at least once per clock tick) with 3 arguments: the "arg"
 * passed at register time, a struct ifnet pointer, and a "count" limit.
 * The registered serializer will be held before calling the related
 * polling handler.
 *
 * The count limit specifies how much work the handler can do during the
 * call -- typically this is the number of packets to be received, or
 * transmitted, etc. (drivers are free to interpret this number, as long
 * as the max time spent in the function grows roughly linearly with the
 * count).
 *
 * A second variable controls the sharing of CPU between polling/kernel
 * network processing, and other activities (typically userlevel tasks):
 * net.ifpoll.{rxX,txX}.user_frac (between 0 and 100, default 50) sets the
 * share of CPU allocated to user tasks.  CPU is allocated proportionally
 * to the shares, by dynamically adjusting the "count" (poll_burst).
 *
 * Other parameters can should be left to their default values.
 * The following constraints hold
 *
 *      1 <= poll_burst <= poll_burst_max
 *      1 <= poll_each_burst <= poll_burst_max
 *      MIN_POLL_BURST_MAX <= poll_burst_max <= MAX_POLL_BURST_MAX
 */

#define IFPOLL_LIST_LEN         128
#define IFPOLL_FREQ_MAX         30000

#define MIN_IOPOLL_BURST_MAX    10
#define MAX_IOPOLL_BURST_MAX    1000
#define IOPOLL_BURST_MAX        150     /* good for 100Mbit net and HZ=1000 */

#define IOPOLL_EACH_BURST       5

#define IFPOLL_FREQ_DEFAULT     2000
#define IOPOLL_FREQ_DEFAULT     IFPOLL_FREQ_DEFAULT
#define STPOLL_FREQ_DEFAULT     100

#define IFPOLL_TXFRAC_DEFAULT   1
#define IFPOLL_STFRAC_DEFAULT   20

#define IFPOLL_RX               0x1
#define IFPOLL_TX               0x2

union ifpoll_time {
        struct timeval          tv;
        uint64_t                tsc;
};

struct iopoll_rec {
        struct lwkt_serialize   *serializer;
        struct ifnet            *ifp;
        void                    *arg;
        ifpoll_iofn_t           poll_func;
};

struct iopoll_ctx {
#ifdef IFPOLL_MULTI_SYSTIMER
        struct systimer         pollclock;
#endif

        union ifpoll_time       prev_t;
        uint32_t                short_ticks;            /* statistics */
        uint32_t                lost_polls;             /* statistics */
        uint32_t                suspect;                /* statistics */
        uint32_t                stalled;                /* statistics */
        uint32_t                pending_polls;          /* state */

        struct netmsg           poll_netmsg;

        int                     poll_cpuid;
#ifdef IFPOLL_MULTI_SYSTIMER
        int                     pollhz;                 /* tunable */
#else
        int                     poll_type;              /* IFPOLL_{RX,TX} */
#endif
        uint32_t                phase;                  /* state */
        int                     residual_burst;         /* state */
        uint32_t                poll_each_burst;        /* tunable */
        union ifpoll_time       poll_start_t;           /* state */

        uint32_t                poll_handlers; /* next free entry in pr[]. */
        struct iopoll_rec       pr[IFPOLL_LIST_LEN];

        struct netmsg           poll_more_netmsg;

        uint32_t                poll_burst;             /* state */
        uint32_t                poll_burst_max;         /* tunable */
        uint32_t                user_frac;              /* tunable */
        uint32_t                kern_frac;              /* state */

        struct sysctl_ctx_list  poll_sysctl_ctx;
        struct sysctl_oid       *poll_sysctl_tree;
} __cachealign;

struct iopoll_comm {
        struct sysctl_ctx_list  sysctl_ctx;
        struct sysctl_oid       *sysctl_tree;
} __cachealign;

struct stpoll_rec {
        struct lwkt_serialize   *serializer;
        struct ifnet            *ifp;
        ifpoll_stfn_t           status_func;
};

struct stpoll_ctx {
#ifdef IFPOLL_MULTI_SYSTIMER
        struct systimer         pollclock;
#endif

        struct netmsg           poll_netmsg;

#ifdef IFPOLL_MULTI_SYSTIMER
        int                     pollhz;                 /* tunable */
#endif
        uint32_t                poll_handlers; /* next free entry in pr[]. */
        struct stpoll_rec       pr[IFPOLL_LIST_LEN];

        struct sysctl_ctx_list  poll_sysctl_ctx;
        struct sysctl_oid       *poll_sysctl_tree;
};

struct iopoll_sysctl_netmsg {
        struct netmsg           nmsg;
        struct iopoll_ctx       *ctx;
};

#ifndef IFPOLL_MULTI_SYSTIMER

struct ifpoll_data {
        struct systimer clock;
        int             txfrac_count;
        int             stfrac_count;
        u_int           tx_cpumask;
        u_int           rx_cpumask;
} __cachealign;

#endif

static struct stpoll_ctx        stpoll_context;
static struct iopoll_comm       *iopoll_common[IFPOLL_CTX_MAX];
static struct iopoll_ctx        *rxpoll_context[IFPOLL_CTX_MAX];
static struct iopoll_ctx        *txpoll_context[IFPOLL_CTX_MAX];

SYSCTL_NODE(_net, OID_AUTO, ifpoll, CTLFLAG_RW, 0,
            "Network device polling parameters");

static int      ifpoll_ncpus = IFPOLL_CTX_MAX;

static int      iopoll_burst_max = IOPOLL_BURST_MAX;
static int      iopoll_each_burst = IOPOLL_EACH_BURST;

TUNABLE_INT("net.ifpoll.burst_max", &iopoll_burst_max);
TUNABLE_INT("net.ifpoll.each_burst", &iopoll_each_burst);

#ifdef IFPOLL_MULTI_SYSTIMER

static int      stpoll_hz = STPOLL_FREQ_DEFAULT;
static int      iopoll_hz = IOPOLL_FREQ_DEFAULT;

TUNABLE_INT("net.ifpoll.stpoll_hz", &stpoll_hz);
TUNABLE_INT("net.ifpoll.iopoll_hz", &iopoll_hz);

#else   /* !IFPOLL_MULTI_SYSTIMER */

static struct ifpoll_data ifpoll0;
static int      ifpoll_pollhz = IFPOLL_FREQ_DEFAULT;
static int      ifpoll_stfrac = IFPOLL_STFRAC_DEFAULT;
static int      ifpoll_txfrac = IFPOLL_TXFRAC_DEFAULT;
static int      ifpoll_handlers;

TUNABLE_INT("net.ifpoll.pollhz", &ifpoll_pollhz);
TUNABLE_INT("net.ifpoll.status_frac", &ifpoll_stfrac);
TUNABLE_INT("net.ifpoll.tx_frac", &ifpoll_txfrac);

static void     sysctl_ifpollhz_handler(struct netmsg *);
static int      sysctl_ifpollhz(SYSCTL_HANDLER_ARGS);

SYSCTL_PROC(_net_ifpoll, OID_AUTO, pollhz, CTLTYPE_INT | CTLFLAG_RW,
            0, 0, sysctl_ifpollhz, "I", "Polling frequency");
SYSCTL_INT(_net_ifpoll, OID_AUTO, tx_frac, CTLFLAG_RW,
           &ifpoll_txfrac, 0, "Every this many cycles poll transmit");
SYSCTL_INT(_net_ifpoll, OID_AUTO, st_frac, CTLFLAG_RW,
           &ifpoll_stfrac, 0, "Every this many cycles poll status");

#endif  /* IFPOLL_MULTI_SYSTIMER */

void            ifpoll_init_pcpu(int);

#ifndef IFPOLL_MULTI_SYSTIMER
static void     ifpoll_start_handler(struct netmsg *);
static void     ifpoll_stop_handler(struct netmsg *);
static void     ifpoll_handler_addevent(void);
static void     ifpoll_handler_delevent(void);
static void     ifpoll_ipi_handler(void *, int);
static void     ifpoll_systimer(systimer_t, struct intrframe *);
#endif

static void     ifpoll_register_handler(struct netmsg *);
static void     ifpoll_deregister_handler(struct netmsg *);

/*
 * Status polling
 */
static void     stpoll_init(void);
static void     stpoll_handler(struct netmsg *);
static void     stpoll_clock(struct stpoll_ctx *);
#ifdef IFPOLL_MULTI_SYSTIMER
static void     stpoll_systimer(systimer_t, struct intrframe *);
#endif
static int      stpoll_register(struct ifnet *, const struct ifpoll_status *);
static int      stpoll_deregister(struct ifnet *);

#ifdef IFPOLL_MULTI_SYSTIMER
static void     sysctl_stpollhz_handler(struct netmsg *);
static int      sysctl_stpollhz(SYSCTL_HANDLER_ARGS);
#endif

/*
 * RX/TX polling
 */
static struct iopoll_ctx *iopoll_ctx_create(int, int);
static struct iopoll_comm *iopoll_comm_create(int);
static void     iopoll_init(int);
static void     iopoll_handler(struct netmsg *);
static void     iopollmore_handler(struct netmsg *);
static void     iopoll_clock(struct iopoll_ctx *);
#ifdef IFPOLL_MULTI_SYSTIMER
static void     iopoll_systimer(systimer_t, struct intrframe *);
#endif
static int      iopoll_register(struct ifnet *, struct iopoll_ctx *,
                    const struct ifpoll_io *);
static int      iopoll_deregister(struct ifnet *, struct iopoll_ctx *);

static void     iopoll_add_sysctl(struct sysctl_ctx_list *,
                    struct sysctl_oid_list *, struct iopoll_ctx *);
#ifdef IFPOLL_MULTI_SYSTIMER
static void     sysctl_iopollhz_handler(struct netmsg *);
static int      sysctl_iopollhz(SYSCTL_HANDLER_ARGS);
#endif
static void     sysctl_burstmax_handler(struct netmsg *);
static int      sysctl_burstmax(SYSCTL_HANDLER_ARGS);
static void     sysctl_eachburst_handler(struct netmsg *);
static int      sysctl_eachburst(SYSCTL_HANDLER_ARGS);

static __inline void
ifpoll_sendmsg_oncpu(struct netmsg *msg)
{
        if (msg->nm_lmsg.ms_flags & MSGF_DONE)
                ifnet_sendmsg(&msg->nm_lmsg, mycpuid);
}

static __inline void
sched_stpoll(struct stpoll_ctx *st_ctx)
{
        ifpoll_sendmsg_oncpu(&st_ctx->poll_netmsg);
}

static __inline void
sched_iopoll(struct iopoll_ctx *io_ctx)
{
        ifpoll_sendmsg_oncpu(&io_ctx->poll_netmsg);
}

static __inline void
sched_iopollmore(struct iopoll_ctx *io_ctx)
{
        ifpoll_sendmsg_oncpu(&io_ctx->poll_more_netmsg);
}

static __inline void
ifpoll_time_get(union ifpoll_time *t)
{
        if (tsc_present)
                t->tsc = rdtsc();
        else
                microuptime(&t->tv);
}

/* Return time diff in us */
static __inline int
ifpoll_time_diff(const union ifpoll_time *s, const union ifpoll_time *e)
{
        if (tsc_present) {
                return (((e->tsc - s->tsc) * 1000000) / tsc_frequency);
        } else {
                return ((e->tv.tv_usec - s->tv.tv_usec) +
                        (e->tv.tv_sec - s->tv.tv_sec) * 1000000);
        }
}

/*
 * Initialize per-cpu qpolling(4) context.  Called from kern_clock.c:
 */
void
ifpoll_init_pcpu(int cpuid)
{
        if (cpuid >= IFPOLL_CTX_MAX) {
                return;
        } else if (cpuid == 0) {
                if (ifpoll_ncpus > ncpus)
                        ifpoll_ncpus = ncpus;
                kprintf("ifpoll_ncpus %d\n", ifpoll_ncpus);

#ifndef IFPOLL_MULTI_SYSTIMER
                systimer_init_periodic_nq(&ifpoll0.clock,
                                          ifpoll_systimer, NULL, 1);
#endif

                stpoll_init();
        }
        iopoll_init(cpuid);
}

#ifndef IFPOLL_MULTI_SYSTIMER

static void
ifpoll_ipi_handler(void *arg __unused, int poll)
{
        KKASSERT(mycpuid < ifpoll_ncpus);

        if (poll & IFPOLL_TX)
                iopoll_clock(txpoll_context[mycpuid]);
        if (poll & IFPOLL_RX)
                iopoll_clock(rxpoll_context[mycpuid]);
}

static void
ifpoll_systimer(systimer_t info __unused, struct intrframe *frame __unused)
{
        uint32_t cpumask = 0;

        KKASSERT(mycpuid == 0);

        if (ifpoll0.stfrac_count-- == 0) {
                ifpoll0.stfrac_count = ifpoll_stfrac;
                stpoll_clock(&stpoll_context);
        }

        if (ifpoll0.txfrac_count-- == 0) {
                ifpoll0.txfrac_count = ifpoll_txfrac;

                /* TODO: We may try to piggyback TX on RX */
                cpumask = smp_active_mask & ifpoll0.tx_cpumask;
                if (cpumask != 0) {
                        lwkt_send_ipiq2_mask(cpumask, ifpoll_ipi_handler,
                                             NULL, IFPOLL_TX);
                }
        }

        cpumask = smp_active_mask & ifpoll0.rx_cpumask;
        if (cpumask != 0) {
                lwkt_send_ipiq2_mask(cpumask, ifpoll_ipi_handler,
                                     NULL, IFPOLL_RX);
        }
}

static void
ifpoll_start_handler(struct netmsg *nmsg)
{
        KKASSERT(&curthread->td_msgport == ifnet_portfn(0));

        kprintf("ifpoll: start\n");
        systimer_adjust_periodic(&ifpoll0.clock, ifpoll_pollhz);
        lwkt_replymsg(&nmsg->nm_lmsg, 0);
}

static void
ifpoll_stop_handler(struct netmsg *nmsg)
{
        KKASSERT(&curthread->td_msgport == ifnet_portfn(0));

        kprintf("ifpoll: stop\n");
        systimer_adjust_periodic(&ifpoll0.clock, 1);
        lwkt_replymsg(&nmsg->nm_lmsg, 0);
}

static void
ifpoll_handler_addevent(void)
{
        if (atomic_fetchadd_int(&ifpoll_handlers, 1) == 0) {
                struct netmsg *nmsg;

                /* Start systimer */
                nmsg = kmalloc(sizeof(*nmsg), M_LWKTMSG, M_WAITOK);
                netmsg_init(nmsg, &netisr_afree_rport, 0, ifpoll_start_handler);
                ifnet_sendmsg(&nmsg->nm_lmsg, 0);
        }
}

static void
ifpoll_handler_delevent(void)
{
        KKASSERT(ifpoll_handlers > 0);
        if (atomic_fetchadd_int(&ifpoll_handlers, -1) == 1) {
                struct netmsg *nmsg;

                /* Stop systimer */
                nmsg = kmalloc(sizeof(*nmsg), M_LWKTMSG, M_WAITOK);
                netmsg_init(nmsg, &netisr_afree_rport, 0, ifpoll_stop_handler);
                ifnet_sendmsg(&nmsg->nm_lmsg, 0);
        }
}

static void
sysctl_ifpollhz_handler(struct netmsg *nmsg)
{
        KKASSERT(&curthread->td_msgport == ifnet_portfn(0));

        /*
         * If there is no handler registered, don't adjust polling
         * systimer frequency; polling systimer frequency will be
         * adjusted once there is registered handler.
         */
        ifpoll_pollhz = nmsg->nm_lmsg.u.ms_result;
        if (ifpoll_handlers)
                systimer_adjust_periodic(&ifpoll0.clock, ifpoll_pollhz);

        lwkt_replymsg(&nmsg->nm_lmsg, 0);
}

static int
sysctl_ifpollhz(SYSCTL_HANDLER_ARGS)
{
        struct netmsg nmsg;
        int error, phz;

        phz = ifpoll_pollhz;
        error = sysctl_handle_int(oidp, &phz, 0, req);
        if (error || req->newptr == NULL)
                return error;
        if (phz <= 0)
                return EINVAL;
        else if (phz > IFPOLL_FREQ_MAX)
                phz = IFPOLL_FREQ_MAX;

        netmsg_init(&nmsg, &curthread->td_msgport, MSGF_MPSAFE,
                    sysctl_ifpollhz_handler);
        nmsg.nm_lmsg.u.ms_result = phz;

        return ifnet_domsg(&nmsg.nm_lmsg, 0);
}

#endif  /* !IFPOLL_MULTI_SYSTIMER */

int
ifpoll_register(struct ifnet *ifp)
{
        struct ifpoll_info info;
        struct netmsg nmsg;
        int error;

        if (ifp->if_qpoll == NULL) {
                /* Device does not support polling */
                return EOPNOTSUPP;
        }

        /*
         * Attempt to register.  Interlock with IFF_NPOLLING.
         */

        ifnet_serialize_all(ifp);

        if (ifp->if_flags & IFF_NPOLLING) {
                /* Already polling */
                ifnet_deserialize_all(ifp);
                return EBUSY;
        }

        bzero(&info, sizeof(info));
        info.ifpi_ifp = ifp;

        ifp->if_flags |= IFF_NPOLLING;
        ifp->if_qpoll(ifp, &info);

        ifnet_deserialize_all(ifp);

        netmsg_init(&nmsg, &curthread->td_msgport, MSGF_MPSAFE,
                    ifpoll_register_handler);
        nmsg.nm_lmsg.u.ms_resultp = &info;

        error = ifnet_domsg(&nmsg.nm_lmsg, 0);
        if (error) {
                if (!ifpoll_deregister(ifp)) {
                        if_printf(ifp, "ifpoll_register: "
                                  "ifpoll_deregister failed!\n");
                }
        }
        return error;
}

int
ifpoll_deregister(struct ifnet *ifp)
{
        struct netmsg nmsg;
        int error;

        if (ifp->if_qpoll == NULL)
                return EOPNOTSUPP;

        ifnet_serialize_all(ifp);

        if ((ifp->if_flags & IFF_NPOLLING) == 0) {
                ifnet_deserialize_all(ifp);
                return EINVAL;
        }
        ifp->if_flags &= ~IFF_NPOLLING;

        ifnet_deserialize_all(ifp);

        netmsg_init(&nmsg, &curthread->td_msgport, MSGF_MPSAFE,
                    ifpoll_deregister_handler);
        nmsg.nm_lmsg.u.ms_resultp = ifp;

        error = ifnet_domsg(&nmsg.nm_lmsg, 0);
        if (!error) {
                ifnet_serialize_all(ifp);
                ifp->if_qpoll(ifp, NULL);
                ifnet_deserialize_all(ifp);
        }
        return error;
}

static void
ifpoll_register_handler(struct netmsg *nmsg)
{
        const struct ifpoll_info *info = nmsg->nm_lmsg.u.ms_resultp;
        int cpuid = mycpuid, nextcpu;
        int error;

        KKASSERT(cpuid < ifpoll_ncpus);
        KKASSERT(&curthread->td_msgport == ifnet_portfn(cpuid));

        if (cpuid == 0) {
                error = stpoll_register(info->ifpi_ifp, &info->ifpi_status);
                if (error)
                        goto failed;
        }

        error = iopoll_register(info->ifpi_ifp, rxpoll_context[cpuid],
                                &info->ifpi_rx[cpuid]);
        if (error)
                goto failed;

        error = iopoll_register(info->ifpi_ifp, txpoll_context[cpuid],
                                &info->ifpi_tx[cpuid]);
        if (error)
                goto failed;

        nextcpu = cpuid + 1;
        if (nextcpu < ifpoll_ncpus)
                ifnet_forwardmsg(&nmsg->nm_lmsg, nextcpu);
        else
                lwkt_replymsg(&nmsg->nm_lmsg, 0);
        return;
failed:
        lwkt_replymsg(&nmsg->nm_lmsg, error);
}

static void
ifpoll_deregister_handler(struct netmsg *nmsg)
{
        struct ifnet *ifp = nmsg->nm_lmsg.u.ms_resultp;
        int cpuid = mycpuid, nextcpu;

        KKASSERT(cpuid < ifpoll_ncpus);
        KKASSERT(&curthread->td_msgport == ifnet_portfn(cpuid));

        /* Ignore errors */
        if (cpuid == 0)
                stpoll_deregister(ifp);
        iopoll_deregister(ifp, rxpoll_context[cpuid]);
        iopoll_deregister(ifp, txpoll_context[cpuid]);

        nextcpu = cpuid + 1;
        if (nextcpu < ifpoll_ncpus)
                ifnet_forwardmsg(&nmsg->nm_lmsg, nextcpu);
        else
                lwkt_replymsg(&nmsg->nm_lmsg, 0);
}

static void
stpoll_init(void)
{
        struct stpoll_ctx *st_ctx = &stpoll_context;

#ifdef IFPOLL_MULTI_SYSTIMER
        st_ctx->pollhz = stpoll_hz;
#endif

        sysctl_ctx_init(&st_ctx->poll_sysctl_ctx);
        st_ctx->poll_sysctl_tree = SYSCTL_ADD_NODE(&st_ctx->poll_sysctl_ctx,
                                   SYSCTL_STATIC_CHILDREN(_net_ifpoll),
                                   OID_AUTO, "status", CTLFLAG_RD, 0, "");

#ifdef IFPOLL_MULTI_SYSTIMER
        SYSCTL_ADD_PROC(&st_ctx->poll_sysctl_ctx,
                        SYSCTL_CHILDREN(st_ctx->poll_sysctl_tree),
                        OID_AUTO, "pollhz", CTLTYPE_INT | CTLFLAG_RW,
                        st_ctx, 0, sysctl_stpollhz, "I",
                        "Status polling frequency");
#endif

        SYSCTL_ADD_UINT(&st_ctx->poll_sysctl_ctx,
                        SYSCTL_CHILDREN(st_ctx->poll_sysctl_tree),
                        OID_AUTO, "handlers", CTLFLAG_RD,
                        &st_ctx->poll_handlers, 0,
                        "Number of registered status poll handlers");

        netmsg_init(&st_ctx->poll_netmsg, &netisr_adone_rport, MSGF_MPSAFE,
                    stpoll_handler);

#ifdef IFPOLL_MULTI_SYSTIMER
        systimer_init_periodic_nq(&st_ctx->pollclock,
                                  stpoll_systimer, st_ctx, 1);
#endif
}

#ifdef IFPOLL_MULTI_SYSTIMER

static void
sysctl_stpollhz_handler(struct netmsg *msg)
{
        struct stpoll_ctx *st_ctx = &stpoll_context;

        KKASSERT(&curthread->td_msgport == ifnet_portfn(0));

        /*
         * If there is no handler registered, don't adjust polling
         * systimer frequency; polling systimer frequency will be
         * adjusted once there is registered handler.
         */
        st_ctx->pollhz = msg->nm_lmsg.u.ms_result;
        if (st_ctx->poll_handlers)
                systimer_adjust_periodic(&st_ctx->pollclock, st_ctx->pollhz);

        lwkt_replymsg(&msg->nm_lmsg, 0);
}

static int
sysctl_stpollhz(SYSCTL_HANDLER_ARGS)
{
        struct stpoll_ctx *st_ctx = arg1;
        struct netmsg msg;
        int error, phz;

        phz = st_ctx->pollhz;
        error = sysctl_handle_int(oidp, &phz, 0, req);
        if (error || req->newptr == NULL)
                return error;
        if (phz <= 0)
                return EINVAL;
        else if (phz > IFPOLL_FREQ_MAX)
                phz = IFPOLL_FREQ_MAX;

        netmsg_init(&msg, &curthread->td_msgport, MSGF_MPSAFE,
                    sysctl_stpollhz_handler);
        msg.nm_lmsg.u.ms_result = phz;

        return ifnet_domsg(&msg.nm_lmsg, 0);
}

#endif  /* IFPOLL_MULTI_SYSTIMER */

/*
 * stpoll_handler is scheduled by sched_stpoll when appropriate, typically
 * once per polling systimer tick.
 */
static void
stpoll_handler(struct netmsg *msg)
{
        struct stpoll_ctx *st_ctx = &stpoll_context;
        struct thread *td = curthread;
        int i, poll_hz;

        KKASSERT(&td->td_msgport == ifnet_portfn(0));

        crit_enter_quick(td);

        /* Reply ASAP */
        lwkt_replymsg(&msg->nm_lmsg, 0);

        if (st_ctx->poll_handlers == 0) {
                crit_exit_quick(td);
                return;
        }

#ifdef IFPOLL_MULTI_SYSTIMER
        poll_hz = st_ctx->pollhz;
#else
        poll_hz = ifpoll_pollhz / (ifpoll_stfrac + 1);
#endif

        for (i = 0; i < st_ctx->poll_handlers; ++i) {
                const struct stpoll_rec *rec = &st_ctx->pr[i];
                struct ifnet *ifp = rec->ifp;

                if (!lwkt_serialize_try(rec->serializer))
                        continue;

                if ((ifp->if_flags & (IFF_RUNNING | IFF_NPOLLING)) ==
                    (IFF_RUNNING | IFF_NPOLLING))
                        rec->status_func(ifp, poll_hz);

                lwkt_serialize_exit(rec->serializer);
        }

        crit_exit_quick(td);
}

/*
 * Hook from status poll systimer.  Tries to schedule an status poll.
 */
static void
stpoll_clock(struct stpoll_ctx *st_ctx)
{
        globaldata_t gd = mycpu;

        KKASSERT(gd->gd_cpuid == 0);

        if (st_ctx->poll_handlers == 0)
                return;

        crit_enter_gd(gd);
        sched_stpoll(st_ctx);
        crit_exit_gd(gd);
}

#ifdef IFPOLL_MULTI_SYSTIMER
static void
stpoll_systimer(systimer_t info, struct intrframe *frame __unused)
{
        stpoll_clock(info->data);
}
#endif

static int
stpoll_register(struct ifnet *ifp, const struct ifpoll_status *st_rec)
{
        struct stpoll_ctx *st_ctx = &stpoll_context;
        int error;

        KKASSERT(&curthread->td_msgport == ifnet_portfn(0));

        if (st_rec->status_func == NULL)
                return 0;

        /*
         * Check if there is room.
         */
        if (st_ctx->poll_handlers >= IFPOLL_LIST_LEN) {
                /*
                 * List full, cannot register more entries.
                 * This should never happen; if it does, it is probably a
                 * broken driver trying to register multiple times. Checking
                 * this at runtime is expensive, and won't solve the problem
                 * anyways, so just report a few times and then give up.
                 */
                static int verbose = 10; /* XXX */

                if (verbose > 0) {
                        kprintf("status poll handlers list full, "
                                "maybe a broken driver ?\n");
                        verbose--;
                }
                error = ENOENT;
        } else {
                struct stpoll_rec *rec = &st_ctx->pr[st_ctx->poll_handlers];

                rec->ifp = ifp;
                rec->serializer = st_rec->serializer;
                rec->status_func = st_rec->status_func;

                st_ctx->poll_handlers++;

#ifdef IFPOLL_MULTI_SYSTIMER
                if (st_ctx->poll_handlers == 1) {
                        systimer_adjust_periodic(&st_ctx->pollclock,
                                                 st_ctx->pollhz);
                }
#else
                ifpoll_handler_addevent();
#endif
                error = 0;
        }
        return error;
}

static int
stpoll_deregister(struct ifnet *ifp)
{
        struct stpoll_ctx *st_ctx = &stpoll_context;
        int i, error;

        KKASSERT(&curthread->td_msgport == ifnet_portfn(0));

        for (i = 0; i < st_ctx->poll_handlers; ++i) {
                if (st_ctx->pr[i].ifp == ifp) /* Found it */
                        break;
        }
        if (i == st_ctx->poll_handlers) {
                kprintf("stpoll_deregister: ifp not found!!!\n");
                error = ENOENT;
        } else {
                st_ctx->poll_handlers--;
                if (i < st_ctx->poll_handlers) {
                        /* Last entry replaces this one. */
                        st_ctx->pr[i] = st_ctx->pr[st_ctx->poll_handlers];
                }

#ifdef IFPOLL_MULTI_SYSTIMER
                if (st_ctx->poll_handlers == 0)
                        systimer_adjust_periodic(&st_ctx->pollclock, 1);
#else
                ifpoll_handler_delevent();
#endif
                error = 0;
        }
        return error;
}

#ifndef IFPOLL_MULTI_SYSTIMER
static __inline int
iopoll_hz(struct iopoll_ctx *io_ctx)
{
        int poll_hz;

        poll_hz = ifpoll_pollhz;
        if (io_ctx->poll_type == IFPOLL_TX)
                poll_hz /= ifpoll_txfrac + 1;
        return poll_hz;
}
#endif

static __inline void
iopoll_reset_state(struct iopoll_ctx *io_ctx)
{
        crit_enter();
        io_ctx->poll_burst = 5;
        io_ctx->pending_polls = 0;
        io_ctx->residual_burst = 0;
        io_ctx->phase = 0;
        io_ctx->kern_frac = 0;
        bzero(&io_ctx->poll_start_t, sizeof(io_ctx->poll_start_t));
        bzero(&io_ctx->prev_t, sizeof(io_ctx->prev_t));
        crit_exit();
}

static void
iopoll_init(int cpuid)
{
        KKASSERT(cpuid < IFPOLL_CTX_MAX);

        /* Create iopoll_comm context before TX/RX poll context */
        iopoll_common[cpuid] = iopoll_comm_create(cpuid);

        rxpoll_context[cpuid] = iopoll_ctx_create(cpuid, IFPOLL_RX);
        txpoll_context[cpuid] = iopoll_ctx_create(cpuid, IFPOLL_TX);
}

static struct iopoll_comm *
iopoll_comm_create(int cpuid)
{
        struct iopoll_comm *comm;
        char cpuid_str[16];

        comm = kmalloc(sizeof(*comm), M_DEVBUF, M_WAITOK | M_ZERO);

        ksnprintf(cpuid_str, sizeof(cpuid_str), "%d", cpuid);

        sysctl_ctx_init(&comm->sysctl_ctx);
        comm->sysctl_tree = SYSCTL_ADD_NODE(&comm->sysctl_ctx,
                            SYSCTL_STATIC_CHILDREN(_net_ifpoll),
                            OID_AUTO, cpuid_str, CTLFLAG_RD, 0, "");

        return comm;
}

static struct iopoll_ctx *
iopoll_ctx_create(int cpuid, int poll_type)
{
        struct iopoll_comm *comm;
        struct iopoll_ctx *io_ctx;
        const char *poll_type_str;

        KKASSERT(poll_type == IFPOLL_RX || poll_type == IFPOLL_TX);

        /*
         * Make sure that tunables are in sane state
         */
        if (iopoll_burst_max < MIN_IOPOLL_BURST_MAX)
                iopoll_burst_max = MIN_IOPOLL_BURST_MAX;
        else if (iopoll_burst_max > MAX_IOPOLL_BURST_MAX)
                iopoll_burst_max = MAX_IOPOLL_BURST_MAX;

        if (iopoll_each_burst > iopoll_burst_max)
                iopoll_each_burst = iopoll_burst_max;

        /*
         * Create the per-cpu polling context
         */
        io_ctx = kmalloc(sizeof(*io_ctx), M_DEVBUF, M_WAITOK | M_ZERO);

        io_ctx->poll_each_burst = iopoll_each_burst;
        io_ctx->poll_burst_max = iopoll_burst_max;
        io_ctx->user_frac = 50;
#ifdef IFPOLL_MULTI_SYSTIMER
        io_ctx->pollhz = iopoll_hz;
#else
        io_ctx->poll_type = poll_type;
#endif
        io_ctx->poll_cpuid = cpuid;
        iopoll_reset_state(io_ctx);

        netmsg_init(&io_ctx->poll_netmsg, &netisr_adone_rport, MSGF_MPSAFE,
                    iopoll_handler);
        io_ctx->poll_netmsg.nm_lmsg.u.ms_resultp = io_ctx;

        netmsg_init(&io_ctx->poll_more_netmsg, &netisr_adone_rport, MSGF_MPSAFE,
                    iopollmore_handler);
        io_ctx->poll_more_netmsg.nm_lmsg.u.ms_resultp = io_ctx;

        /*
         * Initialize per-cpu sysctl nodes
         */
        if (poll_type == IFPOLL_RX)
                poll_type_str = "rx";
        else
                poll_type_str = "tx";

        comm = iopoll_common[cpuid];
        sysctl_ctx_init(&io_ctx->poll_sysctl_ctx);
        io_ctx->poll_sysctl_tree = SYSCTL_ADD_NODE(&io_ctx->poll_sysctl_ctx,
                                   SYSCTL_CHILDREN(comm->sysctl_tree),
                                   OID_AUTO, poll_type_str, CTLFLAG_RD, 0, "");
        iopoll_add_sysctl(&io_ctx->poll_sysctl_ctx,
                          SYSCTL_CHILDREN(io_ctx->poll_sysctl_tree), io_ctx);

#ifdef IFPOLL_MULTI_SYSTIMER
        /*
         * Initialize systimer
         */
        systimer_init_periodic_nq(&io_ctx->pollclock,
                                  iopoll_systimer, io_ctx, 1);
#endif

        return io_ctx;
}

/*
 * Hook from iopoll systimer.  Tries to schedule an iopoll, but keeps
 * track of lost ticks due to the previous handler taking too long.
 * Normally, this should not happen, because polling handler should
 * run for a short time.  However, in some cases (e.g. when there are
 * changes in link status etc.) the drivers take a very long time
 * (even in the order of milliseconds) to reset and reconfigure the
 * device, causing apparent lost polls.
 *
 * The first part of the code is just for debugging purposes, and tries
 * to count how often hardclock ticks are shorter than they should,
 * meaning either stray interrupts or delayed events.
 *
 * WARNING! called from fastint or IPI, the MP lock might not be held.
 */
static void
iopoll_clock(struct iopoll_ctx *io_ctx)
{
        globaldata_t gd = mycpu;
        union ifpoll_time t;
        int delta, poll_hz;

        KKASSERT(gd->gd_cpuid == io_ctx->poll_cpuid);

        if (io_ctx->poll_handlers == 0)
                return;

#ifdef IFPOLL_MULTI_SYSTIMER
        poll_hz = io_ctx->pollhz;
#else
        poll_hz = iopoll_hz(io_ctx);
#endif

        ifpoll_time_get(&t);
        delta = ifpoll_time_diff(&io_ctx->prev_t, &t);
        if (delta * poll_hz < 500000)
                io_ctx->short_ticks++;
        else
                io_ctx->prev_t = t;

        if (io_ctx->pending_polls > 100) {
                /*
                 * Too much, assume it has stalled (not always true
                 * see comment above).
                 */
                io_ctx->stalled++;
                io_ctx->pending_polls = 0;
                io_ctx->phase = 0;
        }

        if (io_ctx->phase <= 2) {
                if (io_ctx->phase != 0)
                        io_ctx->suspect++;
                io_ctx->phase = 1;
                crit_enter_gd(gd);
                sched_iopoll(io_ctx);
                crit_exit_gd(gd);
                io_ctx->phase = 2;
        }
        if (io_ctx->pending_polls++ > 0)
                io_ctx->lost_polls++;
}

#ifdef IFPOLL_MULTI_SYSTIMER
static void
iopoll_systimer(systimer_t info, struct intrframe *frame __unused)
{
        iopoll_clock(info->data);
}
#endif

/*
 * iopoll_handler is scheduled by sched_iopoll when appropriate, typically
 * once per polling systimer tick.
 *
 * Note that the message is replied immediately in order to allow a new
 * ISR to be scheduled in the handler.
 */
static void
iopoll_handler(struct netmsg *msg)
{
        struct iopoll_ctx *io_ctx;
        struct thread *td = curthread;
        int i, cycles;

        io_ctx = msg->nm_lmsg.u.ms_resultp;
        KKASSERT(&td->td_msgport == ifnet_portfn(io_ctx->poll_cpuid));

        crit_enter_quick(td);

        /* Reply ASAP */
        lwkt_replymsg(&msg->nm_lmsg, 0);

        if (io_ctx->poll_handlers == 0) {
                crit_exit_quick(td);
                return;
        }

        io_ctx->phase = 3;
        if (io_ctx->residual_burst == 0) {
                /* First call in this tick */
                ifpoll_time_get(&io_ctx->poll_start_t);
                io_ctx->residual_burst = io_ctx->poll_burst;
        }
        cycles = (io_ctx->residual_burst < io_ctx->poll_each_burst) ?
                 io_ctx->residual_burst : io_ctx->poll_each_burst;
        io_ctx->residual_burst -= cycles;

        for (i = 0; i < io_ctx->poll_handlers; i++) {
                const struct iopoll_rec *rec = &io_ctx->pr[i];
                struct ifnet *ifp = rec->ifp;

                if (!lwkt_serialize_try(rec->serializer))
                        continue;

                if ((ifp->if_flags & (IFF_RUNNING | IFF_NPOLLING)) ==
                    (IFF_RUNNING | IFF_NPOLLING))
                        rec->poll_func(ifp, rec->arg, cycles);

                lwkt_serialize_exit(rec->serializer);
        }

        /*
         * Do a quick exit/enter to catch any higher-priority
         * interrupt sources.
         */
        crit_exit_quick(td);
        crit_enter_quick(td);

        sched_iopollmore(io_ctx);
        io_ctx->phase = 4;

        crit_exit_quick(td);
}

/*
 * iopollmore_handler is called after other netisr's, possibly scheduling
 * another iopoll_handler call, or adapting the burst size for the next cycle.
 *
 * It is very bad to fetch large bursts of packets from a single card at once,
 * because the burst could take a long time to be completely processed leading
 * to unfairness.  To reduce the problem, and also to account better for time
 * spent in network-related processing, we split the burst in smaller chunks
 * of fixed size, giving control to the other netisr's between chunks.  This
 * helps in improving the fairness, reducing livelock and accounting for the
 * work performed in low level handling.
 */
static void
iopollmore_handler(struct netmsg *msg)
{
        struct thread *td = curthread;
        struct iopoll_ctx *io_ctx;
        union ifpoll_time t;
        int kern_load, poll_hz;
        uint32_t pending_polls;

        io_ctx = msg->nm_lmsg.u.ms_resultp;
        KKASSERT(&td->td_msgport == ifnet_portfn(io_ctx->poll_cpuid));

        crit_enter_quick(td);

        /* Replay ASAP */
        lwkt_replymsg(&msg->nm_lmsg, 0);

        if (io_ctx->poll_handlers == 0) {
                crit_exit_quick(td);
                return;
        }

#ifdef IFPOLL_MULTI_SYSTIMER
        poll_hz = io_ctx->pollhz;
#else
        poll_hz = iopoll_hz(io_ctx);
#endif

        io_ctx->phase = 5;
        if (io_ctx->residual_burst > 0) {
                sched_iopoll(io_ctx);
                crit_exit_quick(td);
                /* Will run immediately on return, followed by netisrs */
                return;
        }

        /* Here we can account time spent in iopoll's in this tick */
        ifpoll_time_get(&t);
        kern_load = ifpoll_time_diff(&io_ctx->poll_start_t, &t);
        kern_load = (kern_load * poll_hz) / 10000; /* 0..100 */
        io_ctx->kern_frac = kern_load;

        if (kern_load > (100 - io_ctx->user_frac)) {
                /* Try decrease ticks */
                if (io_ctx->poll_burst > 1)
                        io_ctx->poll_burst--;
        } else {
                if (io_ctx->poll_burst < io_ctx->poll_burst_max)
                        io_ctx->poll_burst++;
        }

        io_ctx->pending_polls--;
        pending_polls = io_ctx->pending_polls;

        if (pending_polls == 0) {
                /* We are done */
                io_ctx->phase = 0;
        } else {
                /*
                 * Last cycle was long and caused us to miss one or more
                 * hardclock ticks.  Restart processing again, but slightly
                 * reduce the burst size to prevent that this happens again.
                 */
                io_ctx->poll_burst -= (io_ctx->poll_burst / 8);
                if (io_ctx->poll_burst < 1)
                        io_ctx->poll_burst = 1;
                sched_iopoll(io_ctx);
                io_ctx->phase = 6;
        }

        crit_exit_quick(td);
}

static void
iopoll_add_sysctl(struct sysctl_ctx_list *ctx, struct sysctl_oid_list *parent,
                  struct iopoll_ctx *io_ctx)
{
#ifdef IFPOLL_MULTI_SYSTIMER
        SYSCTL_ADD_PROC(ctx, parent, OID_AUTO, "pollhz",
                        CTLTYPE_INT | CTLFLAG_RW, io_ctx, 0, sysctl_iopollhz,
                        "I", "Device polling frequency");
#endif

        SYSCTL_ADD_PROC(ctx, parent, OID_AUTO, "burst_max",
                        CTLTYPE_UINT | CTLFLAG_RW, io_ctx, 0, sysctl_burstmax,
                        "IU", "Max Polling burst size");

        SYSCTL_ADD_PROC(ctx, parent, OID_AUTO, "each_burst",
                        CTLTYPE_UINT | CTLFLAG_RW, io_ctx, 0, sysctl_eachburst,
                        "IU", "Max size of each burst");

        SYSCTL_ADD_UINT(ctx, parent, OID_AUTO, "phase", CTLFLAG_RD,
                        &io_ctx->phase, 0, "Polling phase");

        SYSCTL_ADD_UINT(ctx, parent, OID_AUTO, "suspect", CTLFLAG_RW,
                        &io_ctx->suspect, 0, "suspect event");

        SYSCTL_ADD_UINT(ctx, parent, OID_AUTO, "stalled", CTLFLAG_RW,
                        &io_ctx->stalled, 0, "potential stalls");

        SYSCTL_ADD_UINT(ctx, parent, OID_AUTO, "burst", CTLFLAG_RD,
                        &io_ctx->poll_burst, 0, "Current polling burst size");

        SYSCTL_ADD_UINT(ctx, parent, OID_AUTO, "user_frac", CTLFLAG_RW,
                        &io_ctx->user_frac, 0,
                        "Desired user fraction of cpu time");

        SYSCTL_ADD_UINT(ctx, parent, OID_AUTO, "kern_frac", CTLFLAG_RD,
                        &io_ctx->kern_frac, 0,
                        "Kernel fraction of cpu time");

        SYSCTL_ADD_UINT(ctx, parent, OID_AUTO, "short_ticks", CTLFLAG_RW,
                        &io_ctx->short_ticks, 0,
                        "Hardclock ticks shorter than they should be");

        SYSCTL_ADD_UINT(ctx, parent, OID_AUTO, "lost_polls", CTLFLAG_RW,
                        &io_ctx->lost_polls, 0,
                        "How many times we would have lost a poll tick");

        SYSCTL_ADD_UINT(ctx, parent, OID_AUTO, "pending_polls", CTLFLAG_RD,
                        &io_ctx->pending_polls, 0, "Do we need to poll again");

        SYSCTL_ADD_INT(ctx, parent, OID_AUTO, "residual_burst", CTLFLAG_RD,
                       &io_ctx->residual_burst, 0,
                       "# of residual cycles in burst");

        SYSCTL_ADD_UINT(ctx, parent, OID_AUTO, "handlers", CTLFLAG_RD,
                        &io_ctx->poll_handlers, 0,
                        "Number of registered poll handlers");
}

#ifdef IFPOLL_MULTI_SYSTIMER

static int
sysctl_iopollhz(SYSCTL_HANDLER_ARGS)
{
        struct iopoll_ctx *io_ctx = arg1;
        struct iopoll_sysctl_netmsg msg;
        struct netmsg *nmsg;
        int error, phz;

        phz = io_ctx->pollhz;
        error = sysctl_handle_int(oidp, &phz, 0, req);
        if (error || req->newptr == NULL)
                return error;
        if (phz <= 0)
                return EINVAL;
        else if (phz > IFPOLL_FREQ_MAX)
                phz = IFPOLL_FREQ_MAX;

        nmsg = &msg.nmsg;
        netmsg_init(nmsg, &curthread->td_msgport, MSGF_MPSAFE,
                    sysctl_iopollhz_handler);
        nmsg->nm_lmsg.u.ms_result = phz;
        msg.ctx = io_ctx;

        return ifnet_domsg(&nmsg->nm_lmsg, io_ctx->poll_cpuid);
}

static void
sysctl_iopollhz_handler(struct netmsg *nmsg)
{
        struct iopoll_sysctl_netmsg *msg = (struct iopoll_sysctl_netmsg *)nmsg;
        struct iopoll_ctx *io_ctx;

        io_ctx = msg->ctx;
        KKASSERT(&curthread->td_msgport == ifnet_portfn(io_ctx->poll_cpuid));

        /*
         * If polling is disabled or there is no polling handler
         * registered, don't adjust polling systimer frequency.
         * Polling systimer frequency will be adjusted once there
         * are registered handlers.
         */
        io_ctx->pollhz = nmsg->nm_lmsg.u.ms_result;
        if (io_ctx->poll_handlers)
                systimer_adjust_periodic(&io_ctx->pollclock, io_ctx->pollhz);

        lwkt_replymsg(&nmsg->nm_lmsg, 0);
}

#endif  /* IFPOLL_MULTI_SYSTIMER */

static void
sysctl_burstmax_handler(struct netmsg *nmsg)
{
        struct iopoll_sysctl_netmsg *msg = (struct iopoll_sysctl_netmsg *)nmsg;
        struct iopoll_ctx *io_ctx;

        io_ctx = msg->ctx;
        KKASSERT(&curthread->td_msgport == ifnet_portfn(io_ctx->poll_cpuid));

        io_ctx->poll_burst_max = nmsg->nm_lmsg.u.ms_result;
        if (io_ctx->poll_each_burst > io_ctx->poll_burst_max)
                io_ctx->poll_each_burst = io_ctx->poll_burst_max;
        if (io_ctx->poll_burst > io_ctx->poll_burst_max)
                io_ctx->poll_burst = io_ctx->poll_burst_max;
        if (io_ctx->residual_burst > io_ctx->poll_burst_max)
                io_ctx->residual_burst = io_ctx->poll_burst_max;

        lwkt_replymsg(&nmsg->nm_lmsg, 0);
}

static int
sysctl_burstmax(SYSCTL_HANDLER_ARGS)
{
        struct iopoll_ctx *io_ctx = arg1;
        struct iopoll_sysctl_netmsg msg;
        struct netmsg *nmsg;
        uint32_t burst_max;
        int error;

        burst_max = io_ctx->poll_burst_max;
        error = sysctl_handle_int(oidp, &burst_max, 0, req);
        if (error || req->newptr == NULL)
                return error;
        if (burst_max < MIN_IOPOLL_BURST_MAX)
                burst_max = MIN_IOPOLL_BURST_MAX;
        else if (burst_max > MAX_IOPOLL_BURST_MAX)
                burst_max = MAX_IOPOLL_BURST_MAX;

        nmsg = &msg.nmsg;
        netmsg_init(nmsg, &curthread->td_msgport, MSGF_MPSAFE,
                    sysctl_burstmax_handler);
        nmsg->nm_lmsg.u.ms_result = burst_max;
        msg.ctx = io_ctx;

        return ifnet_domsg(&nmsg->nm_lmsg, io_ctx->poll_cpuid);
}

static void
sysctl_eachburst_handler(struct netmsg *nmsg)
{
        struct iopoll_sysctl_netmsg *msg = (struct iopoll_sysctl_netmsg *)nmsg;
        struct iopoll_ctx *io_ctx;
        uint32_t each_burst;

        io_ctx = msg->ctx;
        KKASSERT(&curthread->td_msgport == ifnet_portfn(io_ctx->poll_cpuid));

        each_burst = nmsg->nm_lmsg.u.ms_result;
        if (each_burst > io_ctx->poll_burst_max)
                each_burst = io_ctx->poll_burst_max;
        else if (each_burst < 1)
                each_burst = 1;
        io_ctx->poll_each_burst = each_burst;

        lwkt_replymsg(&nmsg->nm_lmsg, 0);
}

static int
sysctl_eachburst(SYSCTL_HANDLER_ARGS)
{
        struct iopoll_ctx *io_ctx = arg1;
        struct iopoll_sysctl_netmsg msg;
        struct netmsg *nmsg;
        uint32_t each_burst;
        int error;

        each_burst = io_ctx->poll_each_burst;
        error = sysctl_handle_int(oidp, &each_burst, 0, req);
        if (error || req->newptr == NULL)
                return error;

        nmsg = &msg.nmsg;
        netmsg_init(nmsg, &curthread->td_msgport, MSGF_MPSAFE,
                    sysctl_eachburst_handler);
        nmsg->nm_lmsg.u.ms_result = each_burst;
        msg.ctx = io_ctx;

        return ifnet_domsg(&nmsg->nm_lmsg, io_ctx->poll_cpuid);
}

static int
iopoll_register(struct ifnet *ifp, struct iopoll_ctx *io_ctx,
                const struct ifpoll_io *io_rec)
{
        int error;

        KKASSERT(&curthread->td_msgport == ifnet_portfn(io_ctx->poll_cpuid));

        if (io_rec->poll_func == NULL)
                return 0;

        /*
         * Check if there is room.
         */
        if (io_ctx->poll_handlers >= IFPOLL_LIST_LEN) {
                /*
                 * List full, cannot register more entries.
                 * This should never happen; if it does, it is probably a
                 * broken driver trying to register multiple times. Checking
                 * this at runtime is expensive, and won't solve the problem
                 * anyways, so just report a few times and then give up.
                 */
                static int verbose = 10; /* XXX */
                if (verbose > 0) {
                        kprintf("io poll handlers list full, "
                                "maybe a broken driver ?\n");
                        verbose--;
                }
                error = ENOENT;
        } else {
                struct iopoll_rec *rec = &io_ctx->pr[io_ctx->poll_handlers];

                rec->ifp = ifp;
                rec->serializer = io_rec->serializer;
                rec->arg = io_rec->arg;
                rec->poll_func = io_rec->poll_func;

                io_ctx->poll_handlers++;
                if (io_ctx->poll_handlers == 1) {
#ifdef IFPOLL_MULTI_SYSTIMER
                        systimer_adjust_periodic(&io_ctx->pollclock,
                                                 io_ctx->pollhz);
#else
                        u_int *mask;

                        if (io_ctx->poll_type == IFPOLL_RX)
                                mask = &ifpoll0.rx_cpumask;
                        else
                                mask = &ifpoll0.tx_cpumask;
                        KKASSERT((*mask & mycpu->gd_cpumask) == 0);
                        atomic_set_int(mask, mycpu->gd_cpumask);
#endif
                }
#ifndef IFPOLL_MULTI_SYSTIMER
                ifpoll_handler_addevent();
#endif
                error = 0;
        }
        return error;
}

static int
iopoll_deregister(struct ifnet *ifp, struct iopoll_ctx *io_ctx)
{
        int i, error;

        KKASSERT(&curthread->td_msgport == ifnet_portfn(io_ctx->poll_cpuid));

        for (i = 0; i < io_ctx->poll_handlers; ++i) {
                if (io_ctx->pr[i].ifp == ifp) /* Found it */
                        break;
        }
        if (i == io_ctx->poll_handlers) {
                error = ENOENT;
        } else {
                io_ctx->poll_handlers--;
                if (i < io_ctx->poll_handlers) {
                        /* Last entry replaces this one. */
                        io_ctx->pr[i] = io_ctx->pr[io_ctx->poll_handlers];
                }

                if (io_ctx->poll_handlers == 0) {
#ifdef IFPOLL_MULTI_SYSTIMER
                        systimer_adjust_periodic(&io_ctx->pollclock, 1);
#else
                        u_int *mask;

                        if (io_ctx->poll_type == IFPOLL_RX)
                                mask = &ifpoll0.rx_cpumask;
                        else
                                mask = &ifpoll0.tx_cpumask;
                        KKASSERT(*mask & mycpu->gd_cpumask);
                        atomic_clear_int(mask, mycpu->gd_cpumask);
#endif
                        iopoll_reset_state(io_ctx);
                }
#ifndef IFPOLL_MULTI_SYSTIMER
                ifpoll_handler_delevent();
#endif
                error = 0;
        }
        return error;
}