diff options
Diffstat (limited to 'sys/kern/kern_poll.c')
| -rw-r--r-- | sys/kern/kern_poll.c | 568 |
1 files changed, 568 insertions, 0 deletions
diff --git a/sys/kern/kern_poll.c b/sys/kern/kern_poll.c new file mode 100644 index 0000000..0010452 --- /dev/null +++ b/sys/kern/kern_poll.c @@ -0,0 +1,568 @@ +/*- + * 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. + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include "opt_device_polling.h" + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/kernel.h> +#include <sys/kthread.h> +#include <sys/proc.h> +#include <sys/eventhandler.h> +#include <sys/resourcevar.h> +#include <sys/socket.h> /* needed by net/if.h */ +#include <sys/sockio.h> +#include <sys/sysctl.h> +#include <sys/syslog.h> + +#include <net/if.h> /* for IFF_* flags */ +#include <net/netisr.h> /* for NETISR_POLL */ +#include <net/vnet.h> + +void hardclock_device_poll(void); /* hook from hardclock */ + +static struct mtx poll_mtx; + +/* + * Polling support for [network] device drivers. + * + * Drivers which support this feature can register with the + * polling code. + * + * If registration is successful, the driver must disable interrupts, + * and further I/O is performed through the handler, which is invoked + * (at least once per clock tick) with 3 arguments: the "arg" passed at + * register time (a struct ifnet pointer), a command, and a "count" limit. + * + * The command can be one of the following: + * POLL_ONLY: quick move of "count" packets from input/output queues. + * POLL_AND_CHECK_STATUS: as above, plus check status registers or do + * other more expensive operations. This command is issued periodically + * but less frequently than POLL_ONLY. + * + * 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). + * + * Polling is enabled and disabled via setting IFCAP_POLLING flag on + * the interface. The driver ioctl handler should register interface + * with polling and disable interrupts, if registration was successful. + * + * A second variable controls the sharing of CPU between polling/kernel + * network processing, and other activities (typically userlevel tasks): + * kern.polling.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_each_burst <= poll_burst <= poll_burst_max + * 0 <= poll_each_burst + * MIN_POLL_BURST_MAX <= poll_burst_max <= MAX_POLL_BURST_MAX + */ + +#define MIN_POLL_BURST_MAX 10 +#define MAX_POLL_BURST_MAX 1000 + +static uint32_t poll_burst = 5; +static uint32_t poll_burst_max = 150; /* good for 100Mbit net and HZ=1000 */ +static uint32_t poll_each_burst = 5; + +static SYSCTL_NODE(_kern, OID_AUTO, polling, CTLFLAG_RW, 0, + "Device polling parameters"); + +SYSCTL_UINT(_kern_polling, OID_AUTO, burst, CTLFLAG_RD, + &poll_burst, 0, "Current polling burst size"); + +static int netisr_poll_scheduled; +static int netisr_pollmore_scheduled; +static int poll_shutting_down; + +static int poll_burst_max_sysctl(SYSCTL_HANDLER_ARGS) +{ + uint32_t val = poll_burst_max; + int error; + + error = sysctl_handle_int(oidp, &val, 0, req); + if (error || !req->newptr ) + return (error); + if (val < MIN_POLL_BURST_MAX || val > MAX_POLL_BURST_MAX) + return (EINVAL); + + mtx_lock(&poll_mtx); + poll_burst_max = val; + if (poll_burst > poll_burst_max) + poll_burst = poll_burst_max; + if (poll_each_burst > poll_burst_max) + poll_each_burst = MIN_POLL_BURST_MAX; + mtx_unlock(&poll_mtx); + + return (0); +} +SYSCTL_PROC(_kern_polling, OID_AUTO, burst_max, CTLTYPE_UINT | CTLFLAG_RW, + 0, sizeof(uint32_t), poll_burst_max_sysctl, "I", "Max Polling burst size"); + +static int poll_each_burst_sysctl(SYSCTL_HANDLER_ARGS) +{ + uint32_t val = poll_each_burst; + int error; + + error = sysctl_handle_int(oidp, &val, 0, req); + if (error || !req->newptr ) + return (error); + if (val < 1) + return (EINVAL); + + mtx_lock(&poll_mtx); + if (val > poll_burst_max) { + mtx_unlock(&poll_mtx); + return (EINVAL); + } + poll_each_burst = val; + mtx_unlock(&poll_mtx); + + return (0); +} +SYSCTL_PROC(_kern_polling, OID_AUTO, each_burst, CTLTYPE_UINT | CTLFLAG_RW, + 0, sizeof(uint32_t), poll_each_burst_sysctl, "I", + "Max size of each burst"); + +static uint32_t poll_in_idle_loop=0; /* do we poll in idle loop ? */ +SYSCTL_UINT(_kern_polling, OID_AUTO, idle_poll, CTLFLAG_RW, + &poll_in_idle_loop, 0, "Enable device polling in idle loop"); + +static uint32_t user_frac = 50; +static int user_frac_sysctl(SYSCTL_HANDLER_ARGS) +{ + uint32_t val = user_frac; + int error; + + error = sysctl_handle_int(oidp, &val, 0, req); + if (error || !req->newptr ) + return (error); + if (val < 0 || val > 99) + return (EINVAL); + + mtx_lock(&poll_mtx); + user_frac = val; + mtx_unlock(&poll_mtx); + + return (0); +} +SYSCTL_PROC(_kern_polling, OID_AUTO, user_frac, CTLTYPE_UINT | CTLFLAG_RW, + 0, sizeof(uint32_t), user_frac_sysctl, "I", + "Desired user fraction of cpu time"); + +static uint32_t reg_frac_count = 0; +static uint32_t reg_frac = 20 ; +static int reg_frac_sysctl(SYSCTL_HANDLER_ARGS) +{ + uint32_t val = reg_frac; + int error; + + error = sysctl_handle_int(oidp, &val, 0, req); + if (error || !req->newptr ) + return (error); + if (val < 1 || val > hz) + return (EINVAL); + + mtx_lock(&poll_mtx); + reg_frac = val; + if (reg_frac_count >= reg_frac) + reg_frac_count = 0; + mtx_unlock(&poll_mtx); + + return (0); +} +SYSCTL_PROC(_kern_polling, OID_AUTO, reg_frac, CTLTYPE_UINT | CTLFLAG_RW, + 0, sizeof(uint32_t), reg_frac_sysctl, "I", + "Every this many cycles check registers"); + +static uint32_t short_ticks; +SYSCTL_UINT(_kern_polling, OID_AUTO, short_ticks, CTLFLAG_RD, + &short_ticks, 0, "Hardclock ticks shorter than they should be"); + +static uint32_t lost_polls; +SYSCTL_UINT(_kern_polling, OID_AUTO, lost_polls, CTLFLAG_RD, + &lost_polls, 0, "How many times we would have lost a poll tick"); + +static uint32_t pending_polls; +SYSCTL_UINT(_kern_polling, OID_AUTO, pending_polls, CTLFLAG_RD, + &pending_polls, 0, "Do we need to poll again"); + +static int residual_burst = 0; +SYSCTL_INT(_kern_polling, OID_AUTO, residual_burst, CTLFLAG_RD, + &residual_burst, 0, "# of residual cycles in burst"); + +static uint32_t poll_handlers; /* next free entry in pr[]. */ +SYSCTL_UINT(_kern_polling, OID_AUTO, handlers, CTLFLAG_RD, + &poll_handlers, 0, "Number of registered poll handlers"); + +static uint32_t phase; +SYSCTL_UINT(_kern_polling, OID_AUTO, phase, CTLFLAG_RD, + &phase, 0, "Polling phase"); + +static uint32_t suspect; +SYSCTL_UINT(_kern_polling, OID_AUTO, suspect, CTLFLAG_RD, + &suspect, 0, "suspect event"); + +static uint32_t stalled; +SYSCTL_UINT(_kern_polling, OID_AUTO, stalled, CTLFLAG_RD, + &stalled, 0, "potential stalls"); + +static uint32_t idlepoll_sleeping; /* idlepoll is sleeping */ +SYSCTL_UINT(_kern_polling, OID_AUTO, idlepoll_sleeping, CTLFLAG_RD, + &idlepoll_sleeping, 0, "idlepoll is sleeping"); + + +#define POLL_LIST_LEN 128 +struct pollrec { + poll_handler_t *handler; + struct ifnet *ifp; +}; + +static struct pollrec pr[POLL_LIST_LEN]; + +static void +poll_shutdown(void *arg, int howto) +{ + + poll_shutting_down = 1; +} + +static void +init_device_poll(void) +{ + + mtx_init(&poll_mtx, "polling", NULL, MTX_DEF); + EVENTHANDLER_REGISTER(shutdown_post_sync, poll_shutdown, NULL, + SHUTDOWN_PRI_LAST); +} +SYSINIT(device_poll, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, init_device_poll, NULL); + + +/* + * Hook from hardclock. Tries to schedule a netisr, 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. + */ +void +hardclock_device_poll(void) +{ + static struct timeval prev_t, t; + int delta; + + if (poll_handlers == 0 || poll_shutting_down) + return; + + microuptime(&t); + delta = (t.tv_usec - prev_t.tv_usec) + + (t.tv_sec - prev_t.tv_sec)*1000000; + if (delta * hz < 500000) + short_ticks++; + else + prev_t = t; + + if (pending_polls > 100) { + /* + * Too much, assume it has stalled (not always true + * see comment above). + */ + stalled++; + pending_polls = 0; + phase = 0; + } + + if (phase <= 2) { + if (phase != 0) + suspect++; + phase = 1; + netisr_poll_scheduled = 1; + netisr_pollmore_scheduled = 1; + netisr_sched_poll(); + phase = 2; + } + if (pending_polls++ > 0) + lost_polls++; +} + +/* + * ether_poll is called from the idle loop. + */ +static void +ether_poll(int count) +{ + int i; + + mtx_lock(&poll_mtx); + + if (count > poll_each_burst) + count = poll_each_burst; + + for (i = 0 ; i < poll_handlers ; i++) + pr[i].handler(pr[i].ifp, POLL_ONLY, count); + + mtx_unlock(&poll_mtx); +} + +/* + * netisr_pollmore is called after other netisr's, possibly scheduling + * another NETISR_POLL 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, or + * could saturate the intermediate queue (ipintrq or similar) leading to + * losses or 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 (because we + * emulate more closely the "process to completion" that we have with + * fastforwarding) and accounting for the work performed in low level + * handling and forwarding. + */ + +static struct timeval poll_start_t; + +void +netisr_pollmore() +{ + struct timeval t; + int kern_load; + + mtx_lock(&poll_mtx); + if (!netisr_pollmore_scheduled) { + mtx_unlock(&poll_mtx); + return; + } + netisr_pollmore_scheduled = 0; + phase = 5; + if (residual_burst > 0) { + netisr_poll_scheduled = 1; + netisr_pollmore_scheduled = 1; + netisr_sched_poll(); + mtx_unlock(&poll_mtx); + /* will run immediately on return, followed by netisrs */ + return; + } + /* here we can account time spent in netisr's in this tick */ + microuptime(&t); + kern_load = (t.tv_usec - poll_start_t.tv_usec) + + (t.tv_sec - poll_start_t.tv_sec)*1000000; /* us */ + kern_load = (kern_load * hz) / 10000; /* 0..100 */ + if (kern_load > (100 - user_frac)) { /* try decrease ticks */ + if (poll_burst > 1) + poll_burst--; + } else { + if (poll_burst < poll_burst_max) + poll_burst++; + } + + pending_polls--; + if (pending_polls == 0) /* we are done */ + 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. + */ + poll_burst -= (poll_burst / 8); + if (poll_burst < 1) + poll_burst = 1; + netisr_poll_scheduled = 1; + netisr_pollmore_scheduled = 1; + netisr_sched_poll(); + phase = 6; + } + mtx_unlock(&poll_mtx); +} + +/* + * netisr_poll is typically scheduled once per tick. + */ +void +netisr_poll(void) +{ + int i, cycles; + enum poll_cmd arg = POLL_ONLY; + + mtx_lock(&poll_mtx); + if (!netisr_poll_scheduled) { + mtx_unlock(&poll_mtx); + return; + } + netisr_poll_scheduled = 0; + phase = 3; + if (residual_burst == 0) { /* first call in this tick */ + microuptime(&poll_start_t); + if (++reg_frac_count == reg_frac) { + arg = POLL_AND_CHECK_STATUS; + reg_frac_count = 0; + } + + residual_burst = poll_burst; + } + cycles = (residual_burst < poll_each_burst) ? + residual_burst : poll_each_burst; + residual_burst -= cycles; + + for (i = 0 ; i < poll_handlers ; i++) + pr[i].handler(pr[i].ifp, arg, cycles); + + phase = 4; + mtx_unlock(&poll_mtx); +} + +/* + * Try to register routine for polling. Returns 0 if successful + * (and polling should be enabled), error code otherwise. + * A device is not supposed to register itself multiple times. + * + * This is called from within the *_ioctl() functions. + */ +int +ether_poll_register(poll_handler_t *h, struct ifnet *ifp) +{ + int i; + + KASSERT(h != NULL, ("%s: handler is NULL", __func__)); + KASSERT(ifp != NULL, ("%s: ifp is NULL", __func__)); + + mtx_lock(&poll_mtx); + if (poll_handlers >= POLL_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 ; + if (verbose >0) { + log(LOG_ERR, "poll handlers list full, " + "maybe a broken driver ?\n"); + verbose--; + } + mtx_unlock(&poll_mtx); + return (ENOMEM); /* no polling for you */ + } + + for (i = 0 ; i < poll_handlers ; i++) + if (pr[i].ifp == ifp && pr[i].handler != NULL) { + mtx_unlock(&poll_mtx); + log(LOG_DEBUG, "ether_poll_register: %s: handler" + " already registered\n", ifp->if_xname); + return (EEXIST); + } + + pr[poll_handlers].handler = h; + pr[poll_handlers].ifp = ifp; + poll_handlers++; + mtx_unlock(&poll_mtx); + if (idlepoll_sleeping) + wakeup(&idlepoll_sleeping); + return (0); +} + +/* + * Remove interface from the polling list. Called from *_ioctl(), too. + */ +int +ether_poll_deregister(struct ifnet *ifp) +{ + int i; + + KASSERT(ifp != NULL, ("%s: ifp is NULL", __func__)); + + mtx_lock(&poll_mtx); + + for (i = 0 ; i < poll_handlers ; i++) + if (pr[i].ifp == ifp) /* found it */ + break; + if (i == poll_handlers) { + log(LOG_DEBUG, "ether_poll_deregister: %s: not found!\n", + ifp->if_xname); + mtx_unlock(&poll_mtx); + return (ENOENT); + } + poll_handlers--; + if (i < poll_handlers) { /* Last entry replaces this one. */ + pr[i].handler = pr[poll_handlers].handler; + pr[i].ifp = pr[poll_handlers].ifp; + } + mtx_unlock(&poll_mtx); + return (0); +} + +static void +poll_idle(void) +{ + struct thread *td = curthread; + struct rtprio rtp; + + rtp.prio = RTP_PRIO_MAX; /* lowest priority */ + rtp.type = RTP_PRIO_IDLE; + PROC_SLOCK(td->td_proc); + rtp_to_pri(&rtp, td); + PROC_SUNLOCK(td->td_proc); + + for (;;) { + if (poll_in_idle_loop && poll_handlers > 0) { + idlepoll_sleeping = 0; + ether_poll(poll_each_burst); + thread_lock(td); + mi_switch(SW_VOL, NULL); + thread_unlock(td); + } else { + idlepoll_sleeping = 1; + tsleep(&idlepoll_sleeping, 0, "pollid", hz * 3); + } + } +} + +static struct proc *idlepoll; +static struct kproc_desc idlepoll_kp = { + "idlepoll", + poll_idle, + &idlepoll +}; +SYSINIT(idlepoll, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, kproc_start, + &idlepoll_kp); |
