/*-
* 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.
* 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 */
stalled++;
printf("poll stalled [%d] in phase %d\n",
stalled, phase);
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)
