kernel - cleanup vfs_cache debugging

[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/microtime_pcpu.h>

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

#include <net/if.h>
#include <net/if_poll.h>
#include <net/netmsg2.h>
#include <net/netisr2.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_npoll 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)
 *
 * RX is polled at the specified polling frequency (net.ifpoll.X.pollhz).
 * TX and status polling could be done at lower frequency than RX frequency
 * (net.ifpoll.0.status_frac and net.ifpoll.X.tx_frac).  To avoid systimer
 * staggering at high frequency, RX systimer gives TX and status polling a
 * piggyback (XXX).
 *
 * 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_npoll) 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.X.{rx,tx}.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    5000
#define IOPOLL_BURST_MAX        250     /* good for 1000Mbit net and HZ=6000 */

#define IOPOLL_EACH_BURST       50
#define IOPOLL_USER_FRAC        50

#define IFPOLL_FREQ_DEFAULT     6000

#define IFPOLL_TXFRAC_DEFAULT   1       /* 1/1 of the pollhz */
#define IFPOLL_STFRAC_DEFAULT   120     /* 1/120 of the pollhz */

#define IFPOLL_RX               0x1
#define IFPOLL_TX               0x2

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

struct iopoll_ctx {
        union microtime_pcpu    prev_t;
        u_long                  short_ticks;            /* statistics */
        u_long                  lost_polls;             /* statistics */
        u_long                  suspect;                /* statistics */
        u_long                  stalled;                /* statistics */
        uint32_t                pending_polls;          /* state */

        struct netmsg_base      poll_netmsg;
        struct netmsg_base      poll_more_netmsg;

        int                     poll_cpuid;
        int                     pollhz;
        uint32_t                phase;                  /* state */
        int                     residual_burst;         /* state */
        uint32_t                poll_each_burst;        /* tunable */
        union microtime_pcpu    poll_start_t;           /* state */

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

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

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

struct poll_comm {
        struct systimer         pollclock;
        int                     poll_cpuid;

        int                     stfrac_count;           /* state */
        int                     poll_stfrac;            /* tunable */

        int                     txfrac_count;           /* state */
        int                     poll_txfrac;            /* tunable */

        int                     pollhz;                 /* tunable */

        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 {
        struct netmsg_base      poll_netmsg;

        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;
} __cachealign;

struct iopoll_sysctl_netmsg {
        struct netmsg_base      base;
        struct iopoll_ctx       *ctx;
};

void            ifpoll_init_pcpu(int);
static void     ifpoll_register_handler(netmsg_t);
static void     ifpoll_deregister_handler(netmsg_t);

/*
 * Status polling
 */
static void     stpoll_init(void);
static void     stpoll_handler(netmsg_t);
static void     stpoll_clock(struct stpoll_ctx *);
static int      stpoll_register(struct ifnet *, const struct ifpoll_status *);
static int      stpoll_deregister(struct ifnet *);

/*
 * RX/TX polling
 */
static struct iopoll_ctx *iopoll_ctx_create(int, int);
static void     iopoll_init(int);
static void     rxpoll_handler(netmsg_t);
static void     txpoll_handler(netmsg_t);
static void     rxpollmore_handler(netmsg_t);
static void     txpollmore_handler(netmsg_t);
static void     iopoll_clock(struct iopoll_ctx *);
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 *, int);
static void     sysctl_burstmax_handler(netmsg_t);
static int      sysctl_burstmax(SYSCTL_HANDLER_ARGS);
static void     sysctl_eachburst_handler(netmsg_t);
static int      sysctl_eachburst(SYSCTL_HANDLER_ARGS);

/*
 * Common functions
 */
static void     poll_comm_init(int);
static void     poll_comm_start(int);
static void     poll_comm_adjust_pollhz(struct poll_comm *);
static void     poll_comm_systimer0(systimer_t, int, struct intrframe *);
static void     poll_comm_systimer(systimer_t, int, struct intrframe *);
static void     sysctl_pollhz_handler(netmsg_t);
static void     sysctl_stfrac_handler(netmsg_t);
static void     sysctl_txfrac_handler(netmsg_t);
static int      sysctl_pollhz(SYSCTL_HANDLER_ARGS);
static int      sysctl_stfrac(SYSCTL_HANDLER_ARGS);
static int      sysctl_txfrac(SYSCTL_HANDLER_ARGS);
static int      sysctl_compat_npoll_stfrac(SYSCTL_HANDLER_ARGS);
static int      sysctl_compat_npoll_cpuid(SYSCTL_HANDLER_ARGS);

static struct stpoll_ctx        stpoll_context;
static struct poll_comm         *poll_common[MAXCPU];
static struct iopoll_ctx        *rxpoll_context[MAXCPU];
static struct iopoll_ctx        *txpoll_context[MAXCPU];

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

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

static int      ifpoll_pollhz = IFPOLL_FREQ_DEFAULT;
static int      ifpoll_stfrac = IFPOLL_STFRAC_DEFAULT;
static int      ifpoll_txfrac = IFPOLL_TXFRAC_DEFAULT;

TUNABLE_INT("net.ifpoll.burst_max", &iopoll_burst_max);
TUNABLE_INT("net.ifpoll.each_burst", &iopoll_each_burst);
TUNABLE_INT("net.ifpoll.user_frac", &iopoll_user_frac);
TUNABLE_INT("net.ifpoll.pollhz", &ifpoll_pollhz);
TUNABLE_INT("net.ifpoll.status_frac", &ifpoll_stfrac);
TUNABLE_INT("net.ifpoll.tx_frac", &ifpoll_txfrac);

#if !defined(KTR_IF_POLL)
#define  KTR_IF_POLL            KTR_ALL
#endif
KTR_INFO_MASTER(if_poll);
KTR_INFO(KTR_IF_POLL, if_poll, rx_start, 0, "rx start");
KTR_INFO(KTR_IF_POLL, if_poll, rx_end, 1, "rx end");
KTR_INFO(KTR_IF_POLL, if_poll, tx_start, 2, "tx start");
KTR_INFO(KTR_IF_POLL, if_poll, tx_end, 3, "tx end");
KTR_INFO(KTR_IF_POLL, if_poll, rx_mstart, 4, "rx more start");
KTR_INFO(KTR_IF_POLL, if_poll, rx_mend, 5, "rx more end");
KTR_INFO(KTR_IF_POLL, if_poll, tx_mstart, 6, "tx more start");
KTR_INFO(KTR_IF_POLL, if_poll, tx_mend, 7, "tx more end");
KTR_INFO(KTR_IF_POLL, if_poll, ioclock_start, 8, "ioclock start");
KTR_INFO(KTR_IF_POLL, if_poll, ioclock_end, 9, "ioclock end");
#define logpoll(name)   KTR_LOG(if_poll_ ## name)

#define IFPOLL_FREQ_ADJ(comm)   (((comm)->poll_cpuid * 3) % 50)

static __inline int
poll_comm_pollhz_div(const struct poll_comm *comm, int pollhz)
{
        return pollhz + IFPOLL_FREQ_ADJ(comm);
}

static __inline int
poll_comm_pollhz_conv(const struct poll_comm *comm, int pollhz)
{
        return pollhz - IFPOLL_FREQ_ADJ(comm);
}

static __inline void
ifpoll_sendmsg_oncpu(netmsg_t msg)
{
        if (msg->lmsg.ms_flags & MSGF_DONE)
                lwkt_sendmsg_oncpu(netisr_cpuport(mycpuid), &msg->lmsg);
}

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

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

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

/*
 * Initialize per-cpu polling(4) context.  Called from kern_clock.c:
 */
void
ifpoll_init_pcpu(int cpuid)
{
        if (cpuid >= ncpus2)
                return;

        poll_comm_init(cpuid);

        if (cpuid == 0)
                stpoll_init();
        iopoll_init(cpuid);

        poll_comm_start(cpuid);
}

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

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

        info = kmalloc(sizeof(*info), M_TEMP, M_WAITOK | M_ZERO);

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

        ifnet_serialize_all(ifp);

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

        info->ifpi_ifp = ifp;

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

        ifnet_deserialize_all(ifp);

        netmsg_init(&nmsg, NULL, &curthread->td_msgport,
                    0, ifpoll_register_handler);
        nmsg.lmsg.u.ms_resultp = info;

        error = lwkt_domsg(netisr_cpuport(0), &nmsg.lmsg, 0);
        if (error) {
                if (!ifpoll_deregister(ifp)) {
                        if_printf(ifp, "ifpoll_register: "
                                  "ifpoll_deregister failed!\n");
                }
        }

        kfree(info, M_TEMP);
        return error;
}

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

        if (ifp->if_npoll == 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, NULL, &curthread->td_msgport,
                    0, ifpoll_deregister_handler);
        nmsg.lmsg.u.ms_resultp = ifp;

        error = lwkt_domsg(netisr_cpuport(0), &nmsg.lmsg, 0);
        if (!error) {
                ifnet_serialize_all(ifp);
                ifp->if_npoll(ifp, NULL);
                ifnet_deserialize_all(ifp);
        }
        return error;
}

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

        KKASSERT(cpuid < ncpus2);
        KKASSERT(&curthread->td_msgport == netisr_cpuport(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;

        /* Adjust polling frequency, after all registration is done */
        poll_comm_adjust_pollhz(poll_common[cpuid]);

        nextcpu = cpuid + 1;
        if (nextcpu < ncpus2)
                lwkt_forwardmsg(netisr_cpuport(nextcpu), &nmsg->lmsg);
        else
                lwkt_replymsg(&nmsg->lmsg, 0);
        return;
failed:
        lwkt_replymsg(&nmsg->lmsg, error);
}

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

        KKASSERT(cpuid < ncpus2);
        KKASSERT(&curthread->td_msgport == netisr_cpuport(cpuid));

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

        /* Adjust polling frequency, after all deregistration is done */
        poll_comm_adjust_pollhz(poll_common[cpuid]);

        nextcpu = cpuid + 1;
        if (nextcpu < ncpus2)
                lwkt_forwardmsg(netisr_cpuport(nextcpu), &nmsg->lmsg);
        else
                lwkt_replymsg(&nmsg->lmsg, 0);
}

static void
stpoll_init(void)
{
        struct stpoll_ctx *st_ctx = &stpoll_context;
        const struct poll_comm *comm = poll_common[0];

        sysctl_ctx_init(&st_ctx->poll_sysctl_ctx);
        st_ctx->poll_sysctl_tree = SYSCTL_ADD_NODE(&st_ctx->poll_sysctl_ctx,
                                   SYSCTL_CHILDREN(comm->sysctl_tree),
                                   OID_AUTO, "status", CTLFLAG_RD, 0, "");

        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, NULL, &netisr_adone_rport,
                    0, stpoll_handler);
}

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

        ASSERT_IS_NETISR(td, 0);

        crit_enter_quick(td);

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

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

        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);

                lwkt_serialize_exit(rec->serializer);
        }

        crit_exit_quick(td);
}

/*
 * Hook from status poll systimer.  Tries to schedule an status poll.
 * NOTE: Caller should hold critical section.
 */
static void
stpoll_clock(struct stpoll_ctx *st_ctx)
{
        KKASSERT(mycpuid == 0);

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

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

        ASSERT_IN_NETISR(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++;
                error = 0;
        }
        return error;
}

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

        ASSERT_IN_NETISR(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) {
                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];
                }
                error = 0;
        }
        return error;
}

static __inline void
iopoll_reset_state(struct iopoll_ctx *io_ctx)
{
        crit_enter();
        io_ctx->poll_burst = io_ctx->poll_each_burst;
        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 < ncpus2);

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

static struct iopoll_ctx *
iopoll_ctx_create(int cpuid, int poll_type)
{
        struct poll_comm *comm;
        struct iopoll_ctx *io_ctx;
        const char *poll_type_str;
        netisr_fn_t handler, more_handler;

        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;

        comm = poll_common[cpuid];

        /*
         * Create the per-cpu polling context
         */
        io_ctx = kmalloc_cachealign(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 = iopoll_user_frac;
        if (poll_type == IFPOLL_RX)
                io_ctx->pollhz = comm->pollhz;
        else
                io_ctx->pollhz = comm->pollhz / (comm->poll_txfrac + 1);
        io_ctx->poll_cpuid = cpuid;
        iopoll_reset_state(io_ctx);

        if (poll_type == IFPOLL_RX) {
                handler = rxpoll_handler;
                more_handler = rxpollmore_handler;
        } else {
                handler = txpoll_handler;
                more_handler = txpollmore_handler;
        }

        netmsg_init(&io_ctx->poll_netmsg, NULL, &netisr_adone_rport,
            0, handler);
        io_ctx->poll_netmsg.lmsg.u.ms_resultp = io_ctx;

        netmsg_init(&io_ctx->poll_more_netmsg, NULL, &netisr_adone_rport,
            0, more_handler);
        io_ctx->poll_more_netmsg.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";

        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, poll_type);

        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.
 * NOTE: Caller should hold critical section.
 */
static void
iopoll_clock(struct iopoll_ctx *io_ctx)
{
        union microtime_pcpu t;
        int delta;

        KKASSERT(mycpuid == io_ctx->poll_cpuid);

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

        logpoll(ioclock_start);

        microtime_pcpu_get(&t);
        delta = microtime_pcpu_diff(&io_ctx->prev_t, &t);
        if (delta * io_ctx->pollhz < 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;
                sched_iopoll(io_ctx);
                io_ctx->phase = 2;
        }
        if (io_ctx->pending_polls++ > 0)
                io_ctx->lost_polls++;

        logpoll(ioclock_end);
}

/*
 * rxpoll_handler and txpoll_handler are 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
rxpoll_handler(netmsg_t msg)
{
        struct iopoll_ctx *io_ctx;
        struct thread *td = curthread;
        int i, cycles;

        logpoll(rx_start);

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

        crit_enter_quick(td);

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

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

        io_ctx->phase = 3;
        if (io_ctx->residual_burst == 0) {
                /* First call in this tick */
                microtime_pcpu_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);

        logpoll(rx_end);
}

static void
txpoll_handler(netmsg_t msg)
{
        struct iopoll_ctx *io_ctx;
        struct thread *td = curthread;
        int i;

        logpoll(tx_start);

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

        crit_enter_quick(td);

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

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

        io_ctx->phase = 3;

        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, -1);

                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);

        logpoll(tx_end);
}

/*
 * rxpollmore_handler and txpollmore_handler are called after other netisr's,
 * possibly scheduling another rxpoll_handler or txpoll_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
rxpollmore_handler(netmsg_t msg)
{
        struct thread *td = curthread;
        struct iopoll_ctx *io_ctx;
        union microtime_pcpu t;
        int kern_load;
        uint32_t pending_polls;

        logpoll(rx_mstart);

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

        crit_enter_quick(td);

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

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

        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 */
                logpoll(rx_mend);
                return;
        }

        /* Here we can account time spent in iopoll's in this tick */
        microtime_pcpu_get(&t);
        kern_load = microtime_pcpu_diff(&io_ctx->poll_start_t, &t);
        kern_load = (kern_load * io_ctx->pollhz) / 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);

        logpoll(rx_mend);
}

static void
txpollmore_handler(netmsg_t msg)
{
        struct thread *td = curthread;
        struct iopoll_ctx *io_ctx;
        uint32_t pending_polls;

        logpoll(tx_mstart);

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

        crit_enter_quick(td);

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

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

        io_ctx->phase = 5;

        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.
                 */
                sched_iopoll(io_ctx);
                io_ctx->phase = 6;
        }

        crit_exit_quick(td);

        logpoll(tx_mend);
}

static void
iopoll_add_sysctl(struct sysctl_ctx_list *ctx, struct sysctl_oid_list *parent,
    struct iopoll_ctx *io_ctx, int poll_type)
{
        if (poll_type == IFPOLL_RX) {
                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, "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_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, "phase", CTLFLAG_RD,
            &io_ctx->phase, 0, "Polling phase");

        SYSCTL_ADD_ULONG(ctx, parent, OID_AUTO, "suspect", CTLFLAG_RW,
            &io_ctx->suspect, "Suspected events");

        SYSCTL_ADD_ULONG(ctx, parent, OID_AUTO, "stalled", CTLFLAG_RW,
            &io_ctx->stalled, "Potential stalls");

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

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

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

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

        io_ctx->poll_burst_max = nmsg->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->lmsg, 0);
}

static int
sysctl_burstmax(SYSCTL_HANDLER_ARGS)
{
        struct iopoll_ctx *io_ctx = arg1;
        struct iopoll_sysctl_netmsg msg;
        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;

        netmsg_init(&msg.base, NULL, &curthread->td_msgport,
                    0, sysctl_burstmax_handler);
        msg.base.lmsg.u.ms_result = burst_max;
        msg.ctx = io_ctx;

        return lwkt_domsg(netisr_cpuport(io_ctx->poll_cpuid),
            &msg.base.lmsg, 0);
}

static void
sysctl_eachburst_handler(netmsg_t 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 == netisr_cpuport(io_ctx->poll_cpuid));

        each_burst = nmsg->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->lmsg, 0);
}

static int
sysctl_eachburst(SYSCTL_HANDLER_ARGS)
{
        struct iopoll_ctx *io_ctx = arg1;
        struct iopoll_sysctl_netmsg msg;
        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;

        netmsg_init(&msg.base, NULL, &curthread->td_msgport,
                    0, sysctl_eachburst_handler);
        msg.base.lmsg.u.ms_result = each_burst;
        msg.ctx = io_ctx;

        return lwkt_domsg(netisr_cpuport(io_ctx->poll_cpuid),
            &msg.base.lmsg, 0);
}

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

        KKASSERT(&curthread->td_msgport == netisr_cpuport(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++;
                error = 0;
        }
        return error;
}

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

        KKASSERT(&curthread->td_msgport == netisr_cpuport(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)
                        iopoll_reset_state(io_ctx);
                error = 0;
        }
        return error;
}

static void
poll_comm_init(int cpuid)
{
        struct poll_comm *comm;
        char cpuid_str[16];

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

        if (ifpoll_stfrac < 1)
                ifpoll_stfrac = IFPOLL_STFRAC_DEFAULT;
        if (ifpoll_txfrac < 1)
                ifpoll_txfrac = IFPOLL_TXFRAC_DEFAULT;

        comm->poll_cpuid = cpuid;
        comm->pollhz = poll_comm_pollhz_div(comm, ifpoll_pollhz);
        comm->poll_stfrac = ifpoll_stfrac - 1;
        comm->poll_txfrac = ifpoll_txfrac - 1;

        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, "");

        SYSCTL_ADD_PROC(&comm->sysctl_ctx, SYSCTL_CHILDREN(comm->sysctl_tree),
                        OID_AUTO, "pollhz", CTLTYPE_INT | CTLFLAG_RW,
                        comm, 0, sysctl_pollhz,
                        "I", "Device polling frequency");

        if (cpuid == 0) {
                SYSCTL_ADD_PROC(&comm->sysctl_ctx,
                                SYSCTL_CHILDREN(comm->sysctl_tree),
                                OID_AUTO, "status_frac",
                                CTLTYPE_INT | CTLFLAG_RW,
                                comm, 0, sysctl_stfrac,
                                "I", "# of cycles before status is polled");
        }
        SYSCTL_ADD_PROC(&comm->sysctl_ctx, SYSCTL_CHILDREN(comm->sysctl_tree),
                        OID_AUTO, "tx_frac", CTLTYPE_INT | CTLFLAG_RW,
                        comm, 0, sysctl_txfrac,
                        "I", "# of cycles before TX is polled");

        poll_common[cpuid] = comm;
}

static void
poll_comm_start(int cpuid)
{
        struct poll_comm *comm = poll_common[cpuid];
        systimer_func_t func;

        /*
         * Initialize systimer
         */
        if (cpuid == 0)
                func = poll_comm_systimer0;
        else
                func = poll_comm_systimer;
        systimer_init_periodic_nq(&comm->pollclock, func, comm, 1);
}

static void
_poll_comm_systimer(struct poll_comm *comm)
{
        iopoll_clock(rxpoll_context[comm->poll_cpuid]);
        if (comm->txfrac_count-- == 0) {
                comm->txfrac_count = comm->poll_txfrac;
                iopoll_clock(txpoll_context[comm->poll_cpuid]);
        }
}

static void
poll_comm_systimer0(systimer_t info, int in_ipi __unused,
    struct intrframe *frame __unused)
{
        struct poll_comm *comm = info->data;
        globaldata_t gd = mycpu;

        KKASSERT(comm->poll_cpuid == gd->gd_cpuid && gd->gd_cpuid == 0);

        crit_enter_gd(gd);

        if (comm->stfrac_count-- == 0) {
                comm->stfrac_count = comm->poll_stfrac;
                stpoll_clock(&stpoll_context);
        }
        _poll_comm_systimer(comm);

        crit_exit_gd(gd);
}

static void
poll_comm_systimer(systimer_t info, int in_ipi __unused,
    struct intrframe *frame __unused)
{
        struct poll_comm *comm = info->data;
        globaldata_t gd = mycpu;

        KKASSERT(comm->poll_cpuid == gd->gd_cpuid && gd->gd_cpuid != 0);

        crit_enter_gd(gd);
        _poll_comm_systimer(comm);
        crit_exit_gd(gd);
}

static void
poll_comm_adjust_pollhz(struct poll_comm *comm)
{
        uint32_t handlers;
        int pollhz = 1;

        KKASSERT(&curthread->td_msgport == netisr_cpuport(comm->poll_cpuid));

        /*
         * If there is no polling handler registered, set systimer
         * frequency to the lowest value.  Polling systimer frequency
         * will be adjusted to the requested value, once there are
         * registered handlers.
         */
        handlers = rxpoll_context[mycpuid]->poll_handlers +
                   txpoll_context[mycpuid]->poll_handlers;
        if (comm->poll_cpuid == 0)
                handlers += stpoll_context.poll_handlers;
        if (handlers)
                pollhz = comm->pollhz;
        systimer_adjust_periodic(&comm->pollclock, pollhz);
}

static int
sysctl_pollhz(SYSCTL_HANDLER_ARGS)
{
        struct poll_comm *comm = arg1;
        struct netmsg_base nmsg;
        int error, phz;

        phz = poll_comm_pollhz_conv(comm, comm->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, NULL, &curthread->td_msgport,
                    0, sysctl_pollhz_handler);
        nmsg.lmsg.u.ms_result = phz;

        return lwkt_domsg(netisr_cpuport(comm->poll_cpuid), &nmsg.lmsg, 0);
}

static void
sysctl_pollhz_handler(netmsg_t nmsg)
{
        struct poll_comm *comm = poll_common[mycpuid];

        KKASSERT(&curthread->td_msgport == netisr_cpuport(comm->poll_cpuid));

        /* Save polling frequency */
        comm->pollhz = poll_comm_pollhz_div(comm, nmsg->lmsg.u.ms_result);

        /*
         * Adjust cached pollhz
         */
        rxpoll_context[mycpuid]->pollhz = comm->pollhz;
        txpoll_context[mycpuid]->pollhz =
            comm->pollhz / (comm->poll_txfrac + 1);

        /*
         * Adjust polling frequency
         */
        poll_comm_adjust_pollhz(comm);

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

static int
sysctl_stfrac(SYSCTL_HANDLER_ARGS)
{
        struct poll_comm *comm = arg1;
        struct netmsg_base nmsg;
        int error, stfrac;

        KKASSERT(comm->poll_cpuid == 0);

        stfrac = comm->poll_stfrac + 1;
        error = sysctl_handle_int(oidp, &stfrac, 0, req);
        if (error || req->newptr == NULL)
                return error;
        if (stfrac < 1)
                return EINVAL;

        netmsg_init(&nmsg, NULL, &curthread->td_msgport,
                    0, sysctl_stfrac_handler);
        nmsg.lmsg.u.ms_result = stfrac - 1;

        return lwkt_domsg(netisr_cpuport(comm->poll_cpuid), &nmsg.lmsg, 0);
}

static void
sysctl_stfrac_handler(netmsg_t nmsg)
{
        struct poll_comm *comm = poll_common[mycpuid];
        int stfrac = nmsg->lmsg.u.ms_result;

        KKASSERT(&curthread->td_msgport == netisr_cpuport(comm->poll_cpuid));

        crit_enter();
        comm->poll_stfrac = stfrac;
        if (comm->stfrac_count > comm->poll_stfrac)
                comm->stfrac_count = comm->poll_stfrac;
        crit_exit();

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

static int
sysctl_txfrac(SYSCTL_HANDLER_ARGS)
{
        struct poll_comm *comm = arg1;
        struct netmsg_base nmsg;
        int error, txfrac;

        txfrac = comm->poll_txfrac + 1;
        error = sysctl_handle_int(oidp, &txfrac, 0, req);
        if (error || req->newptr == NULL)
                return error;
        if (txfrac < 1)
                return EINVAL;

        netmsg_init(&nmsg, NULL, &curthread->td_msgport,
                    0, sysctl_txfrac_handler);
        nmsg.lmsg.u.ms_result = txfrac - 1;

        return lwkt_domsg(netisr_cpuport(comm->poll_cpuid), &nmsg.lmsg, 0);
}

static void
sysctl_txfrac_handler(netmsg_t nmsg)
{
        struct poll_comm *comm = poll_common[mycpuid];
        int txfrac = nmsg->lmsg.u.ms_result;

        KKASSERT(&curthread->td_msgport == netisr_cpuport(comm->poll_cpuid));

        crit_enter();
        comm->poll_txfrac = txfrac;
        if (comm->txfrac_count > comm->poll_txfrac)
                comm->txfrac_count = comm->poll_txfrac;
        crit_exit();

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

void
ifpoll_compat_setup(struct ifpoll_compat *cp,
    struct sysctl_ctx_list *sysctl_ctx,
    struct sysctl_oid *sysctl_tree,
    int unit, struct lwkt_serialize *slz)
{
        cp->ifpc_stcount = 0;
        cp->ifpc_stfrac = ((poll_common[0]->poll_stfrac + 1) *
            howmany(IOPOLL_BURST_MAX, IOPOLL_EACH_BURST)) - 1;

        cp->ifpc_cpuid = unit % ncpus2;
        cp->ifpc_serializer = slz;

        if (sysctl_ctx != NULL && sysctl_tree != NULL) {
                SYSCTL_ADD_PROC(sysctl_ctx, SYSCTL_CHILDREN(sysctl_tree),
                    OID_AUTO, "npoll_stfrac", CTLTYPE_INT | CTLFLAG_RW,
                    cp, 0, sysctl_compat_npoll_stfrac, "I",
                    "polling status frac");
                SYSCTL_ADD_PROC(sysctl_ctx, SYSCTL_CHILDREN(sysctl_tree),
                    OID_AUTO, "npoll_cpuid", CTLTYPE_INT | CTLFLAG_RW,
                    cp, 0, sysctl_compat_npoll_cpuid, "I",
                    "polling cpuid");
        }
}

static int
sysctl_compat_npoll_stfrac(SYSCTL_HANDLER_ARGS)
{
        struct ifpoll_compat *cp = arg1;
        int error = 0, stfrac;

        lwkt_serialize_enter(cp->ifpc_serializer);

        stfrac = cp->ifpc_stfrac + 1;
        error = sysctl_handle_int(oidp, &stfrac, 0, req);
        if (!error && req->newptr != NULL) {
                if (stfrac < 1) {
                        error = EINVAL;
                } else {
                        cp->ifpc_stfrac = stfrac - 1;
                        if (cp->ifpc_stcount > cp->ifpc_stfrac)
                                cp->ifpc_stcount = cp->ifpc_stfrac;
                }
        }

        lwkt_serialize_exit(cp->ifpc_serializer);
        return error;
}

static int
sysctl_compat_npoll_cpuid(SYSCTL_HANDLER_ARGS)
{
        struct ifpoll_compat *cp = arg1;
        int error = 0, cpuid;

        lwkt_serialize_enter(cp->ifpc_serializer);

        cpuid = cp->ifpc_cpuid;
        error = sysctl_handle_int(oidp, &cpuid, 0, req);
        if (!error && req->newptr != NULL) {
                if (cpuid < 0 || cpuid >= ncpus2)
                        error = EINVAL;
                else
                        cp->ifpc_cpuid = cpuid;
        }

        lwkt_serialize_exit(cp->ifpc_serializer);
        return error;
}