/*- * 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 $ * $DragonFly: src/sys/kern/kern_poll.c,v 1.13 2004/06/27 19:40:12 dillon Exp $ */ #include #include #include #include /* needed by net/if.h */ #include #include #include #include /* for vm_page_zero_idle() */ #include /* for IFF_* flags */ #include /* for NETISR_POLL */ /* the two netisr handlers */ static int netisr_poll(struct netmsg *); static int netisr_pollmore(struct netmsg *); 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"); 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"); #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) { netisr_register(NETISR_POLL, cpu0_portfn, netisr_poll); netisr_register(NETISR_POLLMORE, cpu0_portfn, netisr_pollmore); } /* * 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. * * WARNING! called from fastint or IPI, the MP lock might not be held. */ 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; int s = splimp(); 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 */ splx(s); } /* * 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; /* ARGSUSED */ static int netisr_pollmore(struct netmsg *msg) { struct timeval t; int kern_load; int s = splhigh(); lwkt_replymsg(&msg->nm_lmsg, 0); phase = 5; if (residual_burst > 0) { schednetisr(NETISR_POLL); /* will run immediately on return, followed by netisrs */ goto out; } /* 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; } out: splx(s); return(EASYNC); } /* * 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. * * Note that the message is replied immediately in order to allow a new * ISR to be scheduled in the handler. */ /* ARGSUSED */ static int netisr_poll(struct netmsg *msg) { static int reg_frac_count; int i, cycles; enum poll_cmd arg = POLL_ONLY; int s; lwkt_replymsg(&msg->nm_lmsg, 0); s = splimp(); 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_flags &= ~IFF_POLLING; pr[i].handler(pr[i].ifp, POLL_DEREGISTER, 1); } pr[i].handler=NULL; } residual_burst = 0; poll_handlers = 0; } schednetisr(NETISR_POLLMORE); phase = 4; splx(s); return(EASYNC); } /* * 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_flags & 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_flags |= IFF_POLLING; splx(s); 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; int s = splimp(); if ( !ifp || !(ifp->if_flags & IFF_POLLING) ) { splx(s); return 0; } for (i = 0 ; i < poll_handlers ; i++) if (pr[i].ifp == ifp) /* found it */ break; ifp->if_flags &= ~IFF_POLLING; /* found or not... */ if (i == poll_handlers) { splx(s); 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; } splx(s); return 1; } void emergency_poll_enable(const char *name) { if (polling == 0) { polling = 1; printf("%s forced polling on\n", name); } }