diff options
Diffstat (limited to 'sys/kern/kern_poll.c')
| -rw-r--r-- | sys/kern/kern_poll.c | 523 |
1 files changed, 523 insertions, 0 deletions
diff --git a/sys/kern/kern_poll.c b/sys/kern/kern_poll.c new file mode 100644 index 0000000..a197bc0 --- /dev/null +++ b/sys/kern/kern_poll.c @@ -0,0 +1,523 @@ +/*- + * 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. + * + * $FreeBSD$ + */ + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/kernel.h> +#include <sys/socket.h> /* needed by net/if.h */ +#include <sys/sysctl.h> + +#include <net/if.h> /* for IFF_* flags */ +#include <net/netisr.h> /* for NETISR_POLL */ + +#include <sys/proc.h> +#include <sys/resourcevar.h> +#include <sys/kthread.h> + +#ifdef SMP +#ifndef COMPILING_LINT +#error DEVICE_POLLING is not compatible with SMP +#endif +#endif + +static void netisr_poll(void); /* the two netisr handlers */ +void netisr_pollmore(void); + +void init_device_poll(void); /* init routine */ +void hardclock_device_poll(void); /* hook from hardclock */ +void ether_poll(int); /* polling while in trap */ + +/* + * Polling support for [network] device drivers. + * + * Drivers which support this feature try to 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. + * POLL_DEREGISTER: deregister and return to interrupt mode. + * + * The first two commands are only issued if the interface is marked as + * 'IFF_UP and IFF_RUNNING', the last one only if IFF_RUNNING is set. + * + * 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). + * + * Deregistration can be requested by the driver itself (typically in the + * *_stop() routine), or by the polling code, by invoking the handler. + * + * Polling can be globally enabled or disabled with the sysctl variable + * kern.polling.enable (default is 0, disabled) + * + * 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_in_trap <= 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 + +SYSCTL_NODE(_kern, OID_AUTO, polling, CTLFLAG_RW, 0, + "Device polling parameters"); + +static u_int32_t poll_burst = 5; +SYSCTL_UINT(_kern_polling, OID_AUTO, burst, CTLFLAG_RW, + &poll_burst, 0, "Current polling burst size"); + +static u_int32_t poll_each_burst = 5; +SYSCTL_UINT(_kern_polling, OID_AUTO, each_burst, CTLFLAG_RW, + &poll_each_burst, 0, "Max size of each burst"); + +static u_int32_t poll_burst_max = 150; /* good for 100Mbit net and HZ=1000 */ +SYSCTL_UINT(_kern_polling, OID_AUTO, burst_max, CTLFLAG_RW, + &poll_burst_max, 0, "Max Polling burst size"); + +static u_int32_t poll_in_idle_loop=1; /* 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"); + +u_int32_t poll_in_trap; /* used in trap.c */ +SYSCTL_UINT(_kern_polling, OID_AUTO, poll_in_trap, CTLFLAG_RW, + &poll_in_trap, 0, "Poll burst size during a trap"); + +static u_int32_t user_frac = 50; +SYSCTL_UINT(_kern_polling, OID_AUTO, user_frac, CTLFLAG_RW, + &user_frac, 0, "Desired user fraction of cpu time"); + +static u_int32_t reg_frac = 20 ; +SYSCTL_UINT(_kern_polling, OID_AUTO, reg_frac, CTLFLAG_RW, + ®_frac, 0, "Every this many cycles poll register"); + +static u_int32_t short_ticks; +SYSCTL_UINT(_kern_polling, OID_AUTO, short_ticks, CTLFLAG_RW, + &short_ticks, 0, "Hardclock ticks shorter than they should be"); + +static u_int32_t lost_polls; +SYSCTL_UINT(_kern_polling, OID_AUTO, lost_polls, CTLFLAG_RW, + &lost_polls, 0, "How many times we would have lost a poll tick"); + +static u_int32_t pending_polls; +SYSCTL_UINT(_kern_polling, OID_AUTO, pending_polls, CTLFLAG_RW, + &pending_polls, 0, "Do we need to poll again"); + +static int residual_burst = 0; +SYSCTL_INT(_kern_polling, OID_AUTO, residual_burst, CTLFLAG_RW, + &residual_burst, 0, "# of residual cycles in burst"); + +static u_int32_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 int polling = 0; /* global polling enable */ +SYSCTL_UINT(_kern_polling, OID_AUTO, enable, CTLFLAG_RW, + &polling, 0, "Polling enabled"); + +static u_int32_t phase; +SYSCTL_UINT(_kern_polling, OID_AUTO, phase, CTLFLAG_RW, + &phase, 0, "Polling phase"); + +static u_int32_t suspect; +SYSCTL_UINT(_kern_polling, OID_AUTO, suspect, CTLFLAG_RW, + &suspect, 0, "suspect event"); + +static u_int32_t stalled; +SYSCTL_UINT(_kern_polling, OID_AUTO, stalled, CTLFLAG_RW, + &stalled, 0, "potential stalls"); + +static u_int32_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]; + +/* + * register relevant netisr. Called from kern_clock.c: + */ +void +init_device_poll(void) +{ + register_netisr(NETISR_POLL, netisr_poll); +} + +/* + * 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) + 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; + schednetisr(NETISR_POLL); + phase = 2; + } + if (pending_polls++ > 0) + lost_polls++; +} + +/* + * ether_poll is called from the idle loop or from the trap handler. + */ +void +ether_poll(int count) +{ + int i; + + mtx_lock(&Giant); + + if (count > poll_each_burst) + count = poll_each_burst; + for (i = 0 ; i < poll_handlers ; i++) + if (pr[i].handler && (IFF_UP|IFF_RUNNING) == + (pr[i].ifp->if_flags & (IFF_UP|IFF_RUNNING)) ) + pr[i].handler(pr[i].ifp, 0, count); /* quick check */ + mtx_unlock(&Giant); +} + +/* + * 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; + /* XXX run at splhigh() or equivalent */ + + phase = 5; + if (residual_burst > 0) { + schednetisr(NETISR_POLL); + /* 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; + schednetisr(NETISR_POLL); + phase = 6; + } +} + +/* + * netisr_poll is scheduled by schednetisr when appropriate, typically once + * per tick. It is called at splnet() so first thing to do is to upgrade to + * splimp(), and call all registered handlers. + */ +static void +netisr_poll(void) +{ + static int reg_frac_count; + int i, cycles; + enum poll_cmd arg = POLL_ONLY; + mtx_lock(&Giant); + + phase = 3; + if (residual_burst == 0) { /* first call in this tick */ + microuptime(&poll_start_t); + /* + * Check that paremeters are consistent with runtime + * variables. Some of these tests could be done at sysctl + * time, but the savings would be very limited because we + * still have to check against reg_frac_count and + * poll_each_burst. So, instead of writing separate sysctl + * handlers, we do all here. + */ + + if (reg_frac > hz) + reg_frac = hz; + else if (reg_frac < 1) + reg_frac = 1; + if (reg_frac_count > reg_frac) + reg_frac_count = reg_frac - 1; + if (reg_frac_count-- == 0) { + arg = POLL_AND_CHECK_STATUS; + reg_frac_count = reg_frac - 1; + } + if (poll_burst_max < MIN_POLL_BURST_MAX) + poll_burst_max = MIN_POLL_BURST_MAX; + else if (poll_burst_max > MAX_POLL_BURST_MAX) + poll_burst_max = MAX_POLL_BURST_MAX; + + if (poll_each_burst < 1) + poll_each_burst = 1; + else if (poll_each_burst > poll_burst_max) + poll_each_burst = poll_burst_max; + + residual_burst = poll_burst; + } + cycles = (residual_burst < poll_each_burst) ? + residual_burst : poll_each_burst; + residual_burst -= cycles; + + if (polling) { + for (i = 0 ; i < poll_handlers ; i++) + if (pr[i].handler && (IFF_UP|IFF_RUNNING) == + (pr[i].ifp->if_flags & (IFF_UP|IFF_RUNNING)) ) + pr[i].handler(pr[i].ifp, arg, cycles); + } else { /* unregister */ + for (i = 0 ; i < poll_handlers ; i++) { + if (pr[i].handler && + pr[i].ifp->if_flags & IFF_RUNNING) { + pr[i].ifp->if_ipending &= ~IFF_POLLING; + pr[i].handler(pr[i].ifp, POLL_DEREGISTER, 1); + } + pr[i].handler=NULL; + } + residual_burst = 0; + poll_handlers = 0; + } + /* on -stable, schednetisr(NETISR_POLLMORE); */ + phase = 4; + mtx_unlock(&Giant); +} + +/* + * Try to register routine for polling. Returns 1 if successful + * (and polling should be enabled), 0 otherwise. + * A device is not supposed to register itself multiple times. + * + * This is called from within the *_intr() functions, so we do not need + * further locking. + */ +int +ether_poll_register(poll_handler_t *h, struct ifnet *ifp) +{ + int s; + + if (polling == 0) /* polling disabled, cannot register */ + return 0; + if (h == NULL || ifp == NULL) /* bad arguments */ + return 0; + if ( !(ifp->if_flags & IFF_UP) ) /* must be up */ + return 0; + if (ifp->if_ipending & IFF_POLLING) /* already polling */ + return 0; + + s = splhigh(); + 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 ; + splx(s); + if (verbose >0) { + printf("poll handlers list full, " + "maybe a broken driver ?\n"); + verbose--; + } + return 0; /* no polling for you */ + } + + pr[poll_handlers].handler = h; + pr[poll_handlers].ifp = ifp; + poll_handlers++; + ifp->if_ipending |= IFF_POLLING; + splx(s); + if (idlepoll_sleeping) + wakeup(&idlepoll_sleeping); + return 1; /* polling enabled in next call */ +} + +/* + * Remove interface from the polling list. Normally called by *_stop(). + * It is not an error to call it with IFF_POLLING clear, the call is + * sufficiently rare to be preferable to save the space for the extra + * test in each driver in exchange of one additional function call. + */ +int +ether_poll_deregister(struct ifnet *ifp) +{ + int i; + + mtx_lock(&Giant); + if ( !ifp || !(ifp->if_ipending & IFF_POLLING) ) { + mtx_unlock(&Giant); + return 0; + } + for (i = 0 ; i < poll_handlers ; i++) + if (pr[i].ifp == ifp) /* found it */ + break; + ifp->if_ipending &= ~IFF_POLLING; /* found or not... */ + if (i == poll_handlers) { + mtx_unlock(&Giant); + printf("ether_poll_deregister: ifp not found!!!\n"); + return 0; + } + 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(&Giant); + return 1; +} + +static void +poll_idle(void) +{ + struct thread *td = curthread; + struct rtprio rtp; + int pri; + + rtp.prio = RTP_PRIO_MAX; /* lowest priority */ + rtp.type = RTP_PRIO_IDLE; + mtx_lock_spin(&sched_lock); + rtp_to_pri(&rtp, td->td_ksegrp); + pri = td->td_priority; + mtx_unlock_spin(&sched_lock); + + for (;;) { + if (poll_in_idle_loop && poll_handlers > 0) { + idlepoll_sleeping = 0; + mtx_lock(&Giant); + ether_poll(poll_each_burst); + mtx_unlock(&Giant); + mtx_assert(&Giant, MA_NOTOWNED); + mtx_lock_spin(&sched_lock); + setrunqueue(td); + td->td_proc->p_stats->p_ru.ru_nvcsw++; + mi_switch(); + mtx_unlock_spin(&sched_lock); + } else { + idlepoll_sleeping = 1; + tsleep(&idlepoll_sleeping, pri, "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) |
