freebsd-dev/sys/kern/kern_timeout.c
Jonathan Lemon 9b8b58e033 Restructure TCP timeout handling:
- eliminate the fast/slow timeout lists for TCP and instead use a
    callout entry for each timer.
  - increase the TCP timer granularity to HZ
  - implement "bad retransmit" recovery, as presented in
    "On Estimating End-to-End Network Path Properties", by Allman and Paxson.

Submitted by:	jlemon, wollmann
1999-08-30 21:17:07 +00:00

359 lines
10 KiB
C

/*-
* Copyright (c) 1982, 1986, 1991, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*
* From: @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
* $FreeBSD$
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/callout.h>
#include <sys/kernel.h>
/*
* TODO:
* allocate more timeout table slots when table overflows.
*/
/* Exported to machdep.c and/or kern_clock.c. */
struct callout *callout;
struct callout_list callfree;
int callwheelsize, callwheelbits, callwheelmask;
struct callout_tailq *callwheel;
int softticks; /* Like ticks, but for softclock(). */
static struct callout *nextsoftcheck; /* Next callout to be checked. */
/*
* The callout mechanism is based on the work of Adam M. Costello and
* George Varghese, published in a technical report entitled "Redesigning
* the BSD Callout and Timer Facilities" and modified slightly for inclusion
* in FreeBSD by Justin T. Gibbs. The original work on the data structures
* used in this implementation was published by G.Varghese and A. Lauck in
* the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
* the Efficient Implementation of a Timer Facility" in the Proceedings of
* the 11th ACM Annual Symposium on Operating Systems Principles,
* Austin, Texas Nov 1987.
*/
/*
* Software (low priority) clock interrupt.
* Run periodic events from timeout queue.
*/
void
softclock()
{
register struct callout *c;
register struct callout_tailq *bucket;
register int s;
register int curticks;
register int steps; /* #steps since we last allowed interrupts */
#ifndef MAX_SOFTCLOCK_STEPS
#define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
#endif /* MAX_SOFTCLOCK_STEPS */
steps = 0;
s = splhigh();
while (softticks != ticks) {
softticks++;
/*
* softticks may be modified by hard clock, so cache
* it while we work on a given bucket.
*/
curticks = softticks;
bucket = &callwheel[curticks & callwheelmask];
c = TAILQ_FIRST(bucket);
while (c) {
if (c->c_time != curticks) {
c = TAILQ_NEXT(c, c_links.tqe);
++steps;
if (steps >= MAX_SOFTCLOCK_STEPS) {
nextsoftcheck = c;
/* Give interrupts a chance. */
splx(s);
s = splhigh();
c = nextsoftcheck;
steps = 0;
}
} else {
void (*c_func)(void *);
void *c_arg;
nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
TAILQ_REMOVE(bucket, c, c_links.tqe);
c_func = c->c_func;
c_arg = c->c_arg;
c->c_func = NULL;
if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
c->c_flags = CALLOUT_LOCAL_ALLOC;
SLIST_INSERT_HEAD(&callfree, c,
c_links.sle);
} else {
c->c_flags =
(c->c_flags & ~CALLOUT_PENDING);
}
splx(s);
c_func(c_arg);
s = splhigh();
steps = 0;
c = nextsoftcheck;
}
}
}
nextsoftcheck = NULL;
splx(s);
}
/*
* timeout --
* Execute a function after a specified length of time.
*
* untimeout --
* Cancel previous timeout function call.
*
* callout_handle_init --
* Initialize a handle so that using it with untimeout is benign.
*
* See AT&T BCI Driver Reference Manual for specification. This
* implementation differs from that one in that although an
* identification value is returned from timeout, the original
* arguments to timeout as well as the identifier are used to
* identify entries for untimeout.
*/
struct callout_handle
timeout(ftn, arg, to_ticks)
timeout_t *ftn;
void *arg;
register int to_ticks;
{
int s;
struct callout *new;
struct callout_handle handle;
s = splhigh();
/* Fill in the next free callout structure. */
new = SLIST_FIRST(&callfree);
if (new == NULL)
/* XXX Attempt to malloc first */
panic("timeout table full");
SLIST_REMOVE_HEAD(&callfree, c_links.sle);
callout_reset(new, to_ticks, ftn, arg);
handle.callout = new;
splx(s);
return (handle);
}
void
untimeout(ftn, arg, handle)
timeout_t *ftn;
void *arg;
struct callout_handle handle;
{
register int s;
/*
* Check for a handle that was initialized
* by callout_handle_init, but never used
* for a real timeout.
*/
if (handle.callout == NULL)
return;
s = splhigh();
if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
callout_stop(handle.callout);
splx(s);
}
void
callout_handle_init(struct callout_handle *handle)
{
handle->callout = NULL;
}
/*
* New interface; clients allocate their own callout structures.
*
* callout_reset() - establish or change a timeout
* callout_stop() - disestablish a timeout
* callout_init() - initialize a callout structure so that it can
* safely be passed to callout_reset() and callout_stop()
*
* <sys/callout.h> defines three convenience macros:
*
* callout_active() - returns truth if callout has not been serviced
* callout_pending() - returns truth if callout is still waiting for timeout
* callout_deactivate() - marks the callout as having been serviced
*/
void
callout_reset(c, to_ticks, ftn, arg)
struct callout *c;
int to_ticks;
void (*ftn) __P((void *));
void *arg;
{
int s;
s = splhigh();
if (c->c_flags & CALLOUT_PENDING)
callout_stop(c);
/*
* We could spl down here and back up at the TAILQ_INSERT_TAIL,
* but there's no point since doing this setup doesn't take much
* time.
*/
if (to_ticks <= 0)
to_ticks = 1;
c->c_arg = arg;
c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
c->c_func = ftn;
c->c_time = ticks + to_ticks;
TAILQ_INSERT_TAIL(&callwheel[c->c_time & callwheelmask],
c, c_links.tqe);
splx(s);
}
void
callout_stop(c)
struct callout *c;
{
int s;
s = splhigh();
/*
* Don't attempt to delete a callout that's not on the queue.
*/
if (!(c->c_flags & CALLOUT_PENDING)) {
c->c_flags &= ~CALLOUT_ACTIVE;
splx(s);
return;
}
c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
if (nextsoftcheck == c) {
nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
}
TAILQ_REMOVE(&callwheel[c->c_time & callwheelmask], c, c_links.tqe);
c->c_func = NULL;
if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
SLIST_INSERT_HEAD(&callfree, c, c_links.sle);
}
splx(s);
}
void
callout_init(c)
struct callout *c;
{
bzero(c, sizeof *c);
}
#ifdef APM_FIXUP_CALLTODO
/*
* Adjust the kernel calltodo timeout list. This routine is used after
* an APM resume to recalculate the calltodo timer list values with the
* number of hz's we have been sleeping. The next hardclock() will detect
* that there are fired timers and run softclock() to execute them.
*
* Please note, I have not done an exhaustive analysis of what code this
* might break. I am motivated to have my select()'s and alarm()'s that
* have expired during suspend firing upon resume so that the applications
* which set the timer can do the maintanence the timer was for as close
* as possible to the originally intended time. Testing this code for a
* week showed that resuming from a suspend resulted in 22 to 25 timers
* firing, which seemed independant on whether the suspend was 2 hours or
* 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu>
*/
void
adjust_timeout_calltodo(time_change)
struct timeval *time_change;
{
register struct callout *p;
unsigned long delta_ticks;
int s;
/*
* How many ticks were we asleep?
* (stolen from tvtohz()).
*/
/* Don't do anything */
if (time_change->tv_sec < 0)
return;
else if (time_change->tv_sec <= LONG_MAX / 1000000)
delta_ticks = (time_change->tv_sec * 1000000 +
time_change->tv_usec + (tick - 1)) / tick + 1;
else if (time_change->tv_sec <= LONG_MAX / hz)
delta_ticks = time_change->tv_sec * hz +
(time_change->tv_usec + (tick - 1)) / tick + 1;
else
delta_ticks = LONG_MAX;
if (delta_ticks > INT_MAX)
delta_ticks = INT_MAX;
/*
* Now rip through the timer calltodo list looking for timers
* to expire.
*/
/* don't collide with softclock() */
s = splhigh();
for (p = calltodo.c_next; p != NULL; p = p->c_next) {
p->c_time -= delta_ticks;
/* Break if the timer had more time on it than delta_ticks */
if (p->c_time > 0)
break;
/* take back the ticks the timer didn't use (p->c_time <= 0) */
delta_ticks = -p->c_time;
}
splx(s);
return;
}
#endif /* APM_FIXUP_CALLTODO */