7fc735912b
- 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
359 lines
10 KiB
C
359 lines
10 KiB
C
/*-
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* Copyright (c) 1982, 1986, 1991, 1993
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* The Regents of the University of California. All rights reserved.
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* (c) UNIX System Laboratories, Inc.
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* All or some portions of this file are derived from material licensed
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* to the University of California by American Telephone and Telegraph
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* Co. or Unix System Laboratories, Inc. and are reproduced herein with
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* the permission of UNIX System Laboratories, Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* From: @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/callout.h>
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#include <sys/kernel.h>
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/*
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* TODO:
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* allocate more timeout table slots when table overflows.
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*/
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/* Exported to machdep.c and/or kern_clock.c. */
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struct callout *callout;
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struct callout_list callfree;
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int callwheelsize, callwheelbits, callwheelmask;
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struct callout_tailq *callwheel;
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int softticks; /* Like ticks, but for softclock(). */
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static struct callout *nextsoftcheck; /* Next callout to be checked. */
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/*
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* The callout mechanism is based on the work of Adam M. Costello and
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* George Varghese, published in a technical report entitled "Redesigning
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* the BSD Callout and Timer Facilities" and modified slightly for inclusion
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* in FreeBSD by Justin T. Gibbs. The original work on the data structures
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* used in this implementation was published by G.Varghese and A. Lauck in
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* the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
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* the Efficient Implementation of a Timer Facility" in the Proceedings of
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* the 11th ACM Annual Symposium on Operating Systems Principles,
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* Austin, Texas Nov 1987.
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*/
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/*
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* Software (low priority) clock interrupt.
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* Run periodic events from timeout queue.
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*/
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void
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softclock()
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{
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register struct callout *c;
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register struct callout_tailq *bucket;
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register int s;
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register int curticks;
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register int steps; /* #steps since we last allowed interrupts */
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#ifndef MAX_SOFTCLOCK_STEPS
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#define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
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#endif /* MAX_SOFTCLOCK_STEPS */
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steps = 0;
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s = splhigh();
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while (softticks != ticks) {
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softticks++;
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/*
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* softticks may be modified by hard clock, so cache
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* it while we work on a given bucket.
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*/
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curticks = softticks;
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bucket = &callwheel[curticks & callwheelmask];
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c = TAILQ_FIRST(bucket);
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while (c) {
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if (c->c_time != curticks) {
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c = TAILQ_NEXT(c, c_links.tqe);
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++steps;
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if (steps >= MAX_SOFTCLOCK_STEPS) {
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nextsoftcheck = c;
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/* Give interrupts a chance. */
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splx(s);
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s = splhigh();
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c = nextsoftcheck;
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steps = 0;
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}
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} else {
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void (*c_func)(void *);
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void *c_arg;
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nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
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TAILQ_REMOVE(bucket, c, c_links.tqe);
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c_func = c->c_func;
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c_arg = c->c_arg;
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c->c_func = NULL;
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if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
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c->c_flags = CALLOUT_LOCAL_ALLOC;
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SLIST_INSERT_HEAD(&callfree, c,
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c_links.sle);
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} else {
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c->c_flags =
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(c->c_flags & ~CALLOUT_PENDING);
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}
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splx(s);
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c_func(c_arg);
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s = splhigh();
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steps = 0;
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c = nextsoftcheck;
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}
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}
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}
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nextsoftcheck = NULL;
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splx(s);
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}
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/*
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* timeout --
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* Execute a function after a specified length of time.
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*
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* untimeout --
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* Cancel previous timeout function call.
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*
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* callout_handle_init --
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* Initialize a handle so that using it with untimeout is benign.
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*
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* See AT&T BCI Driver Reference Manual for specification. This
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* implementation differs from that one in that although an
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* identification value is returned from timeout, the original
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* arguments to timeout as well as the identifier are used to
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* identify entries for untimeout.
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*/
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struct callout_handle
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timeout(ftn, arg, to_ticks)
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timeout_t *ftn;
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void *arg;
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register int to_ticks;
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{
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int s;
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struct callout *new;
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struct callout_handle handle;
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s = splhigh();
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/* Fill in the next free callout structure. */
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new = SLIST_FIRST(&callfree);
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if (new == NULL)
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/* XXX Attempt to malloc first */
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panic("timeout table full");
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SLIST_REMOVE_HEAD(&callfree, c_links.sle);
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callout_reset(new, to_ticks, ftn, arg);
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handle.callout = new;
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splx(s);
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return (handle);
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}
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void
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untimeout(ftn, arg, handle)
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timeout_t *ftn;
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void *arg;
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struct callout_handle handle;
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{
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register int s;
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/*
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* Check for a handle that was initialized
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* by callout_handle_init, but never used
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* for a real timeout.
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*/
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if (handle.callout == NULL)
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return;
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s = splhigh();
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if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
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callout_stop(handle.callout);
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splx(s);
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}
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void
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callout_handle_init(struct callout_handle *handle)
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{
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handle->callout = NULL;
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}
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/*
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* New interface; clients allocate their own callout structures.
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*
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* callout_reset() - establish or change a timeout
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* callout_stop() - disestablish a timeout
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* callout_init() - initialize a callout structure so that it can
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* safely be passed to callout_reset() and callout_stop()
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*
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* <sys/callout.h> defines three convenience macros:
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*
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* callout_active() - returns truth if callout has not been serviced
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* callout_pending() - returns truth if callout is still waiting for timeout
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* callout_deactivate() - marks the callout as having been serviced
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*/
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void
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callout_reset(c, to_ticks, ftn, arg)
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struct callout *c;
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int to_ticks;
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void (*ftn) __P((void *));
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void *arg;
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{
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int s;
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s = splhigh();
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if (c->c_flags & CALLOUT_PENDING)
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callout_stop(c);
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/*
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* We could spl down here and back up at the TAILQ_INSERT_TAIL,
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* but there's no point since doing this setup doesn't take much
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* time.
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*/
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if (to_ticks <= 0)
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to_ticks = 1;
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c->c_arg = arg;
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c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
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c->c_func = ftn;
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c->c_time = ticks + to_ticks;
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TAILQ_INSERT_TAIL(&callwheel[c->c_time & callwheelmask],
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c, c_links.tqe);
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splx(s);
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}
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void
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callout_stop(c)
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struct callout *c;
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{
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int s;
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s = splhigh();
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/*
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* Don't attempt to delete a callout that's not on the queue.
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*/
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if (!(c->c_flags & CALLOUT_PENDING)) {
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c->c_flags &= ~CALLOUT_ACTIVE;
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splx(s);
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return;
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}
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c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
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if (nextsoftcheck == c) {
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nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
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}
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TAILQ_REMOVE(&callwheel[c->c_time & callwheelmask], c, c_links.tqe);
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c->c_func = NULL;
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if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
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SLIST_INSERT_HEAD(&callfree, c, c_links.sle);
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}
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splx(s);
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}
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void
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callout_init(c)
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struct callout *c;
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{
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bzero(c, sizeof *c);
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}
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#ifdef APM_FIXUP_CALLTODO
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/*
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* Adjust the kernel calltodo timeout list. This routine is used after
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* an APM resume to recalculate the calltodo timer list values with the
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* number of hz's we have been sleeping. The next hardclock() will detect
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* that there are fired timers and run softclock() to execute them.
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*
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* Please note, I have not done an exhaustive analysis of what code this
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* might break. I am motivated to have my select()'s and alarm()'s that
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* have expired during suspend firing upon resume so that the applications
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* which set the timer can do the maintanence the timer was for as close
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* as possible to the originally intended time. Testing this code for a
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* week showed that resuming from a suspend resulted in 22 to 25 timers
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* firing, which seemed independant on whether the suspend was 2 hours or
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* 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu>
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*/
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void
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adjust_timeout_calltodo(time_change)
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struct timeval *time_change;
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{
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register struct callout *p;
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unsigned long delta_ticks;
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int s;
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/*
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* How many ticks were we asleep?
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* (stolen from tvtohz()).
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*/
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/* Don't do anything */
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if (time_change->tv_sec < 0)
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return;
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else if (time_change->tv_sec <= LONG_MAX / 1000000)
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delta_ticks = (time_change->tv_sec * 1000000 +
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time_change->tv_usec + (tick - 1)) / tick + 1;
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else if (time_change->tv_sec <= LONG_MAX / hz)
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delta_ticks = time_change->tv_sec * hz +
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(time_change->tv_usec + (tick - 1)) / tick + 1;
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else
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delta_ticks = LONG_MAX;
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if (delta_ticks > INT_MAX)
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delta_ticks = INT_MAX;
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/*
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* Now rip through the timer calltodo list looking for timers
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* to expire.
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*/
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/* don't collide with softclock() */
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s = splhigh();
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for (p = calltodo.c_next; p != NULL; p = p->c_next) {
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p->c_time -= delta_ticks;
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/* Break if the timer had more time on it than delta_ticks */
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if (p->c_time > 0)
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break;
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/* take back the ticks the timer didn't use (p->c_time <= 0) */
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delta_ticks = -p->c_time;
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}
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splx(s);
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return;
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}
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#endif /* APM_FIXUP_CALLTODO */
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