90035a10c9
- Do timeslicing for SCHED_RR threads. At ~16Hz it's too slow but better than nothing. XXX - If a SCHED_OTHER thread has hogged the CPU for 1/8s without taking a trip through mi_switch(), try to force a kernel preemption to give other threads a chance.
552 lines
15 KiB
C
552 lines
15 KiB
C
/* $NetBSD: sched_4bsd.c,v 1.23 2008/05/25 22:04:50 ad Exp $ */
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/*-
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* Copyright (c) 1999, 2000, 2004, 2006, 2007, 2008 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
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* NASA Ames Research Center, by Charles M. Hannum, Andrew Doran, and
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* Daniel Sieger.
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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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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*-
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* Copyright (c) 1982, 1986, 1990, 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. 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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* @(#)kern_synch.c 8.9 (Berkeley) 5/19/95
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: sched_4bsd.c,v 1.23 2008/05/25 22:04:50 ad Exp $");
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#include "opt_ddb.h"
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#include "opt_lockdebug.h"
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#include "opt_perfctrs.h"
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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/cpu.h>
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#include <sys/proc.h>
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#include <sys/kernel.h>
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#include <sys/signalvar.h>
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#include <sys/resourcevar.h>
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#include <sys/sched.h>
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#include <sys/sysctl.h>
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#include <sys/kauth.h>
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#include <sys/lockdebug.h>
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#include <sys/kmem.h>
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#include <sys/intr.h>
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#include <uvm/uvm_extern.h>
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static void updatepri(struct lwp *);
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static void resetpriority(struct lwp *);
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extern unsigned int sched_pstats_ticks; /* defined in kern_synch.c */
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/* Number of hardclock ticks per sched_tick() */
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static int rrticks;
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/*
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* Force switch among equal priority processes every 100ms.
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* Called from hardclock every hz/10 == rrticks hardclock ticks.
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*
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* There's no need to lock anywhere in this routine, as it's
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* CPU-local and runs at IPL_SCHED (called from clock interrupt).
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*/
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/* ARGSUSED */
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void
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sched_tick(struct cpu_info *ci)
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{
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struct schedstate_percpu *spc = &ci->ci_schedstate;
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lwp_t *l;
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spc->spc_ticks = rrticks;
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if (CURCPU_IDLE_P()) {
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cpu_need_resched(ci, 0);
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return;
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}
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l = ci->ci_data.cpu_onproc;
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if (l == NULL) {
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return;
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}
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switch (l->l_class) {
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case SCHED_FIFO:
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/* No timeslicing for FIFO jobs. */
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break;
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case SCHED_RR:
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/* Force it into mi_switch() to look for other jobs to run. */
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cpu_need_resched(ci, RESCHED_KPREEMPT);
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break;
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default:
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if (spc->spc_flags & SPCF_SHOULDYIELD) {
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/*
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* Process is stuck in kernel somewhere, probably
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* due to buggy or inefficient code. Force a
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* kernel preemption.
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*/
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cpu_need_resched(ci, RESCHED_KPREEMPT);
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} else if (spc->spc_flags & SPCF_SEENRR) {
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/*
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* The process has already been through a roundrobin
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* without switching and may be hogging the CPU.
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* Indicate that the process should yield.
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*/
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spc->spc_flags |= SPCF_SHOULDYIELD;
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cpu_need_resched(ci, 0);
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} else {
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spc->spc_flags |= SPCF_SEENRR;
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}
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break;
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}
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}
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/*
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* Why PRIO_MAX - 2? From setpriority(2):
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*
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* prio is a value in the range -20 to 20. The default priority is
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* 0; lower priorities cause more favorable scheduling. A value of
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* 19 or 20 will schedule a process only when nothing at priority <=
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* 0 is runnable.
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*
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* This gives estcpu influence over 18 priority levels, and leaves nice
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* with 40 levels. One way to think about it is that nice has 20 levels
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* either side of estcpu's 18.
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*/
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#define ESTCPU_SHIFT 11
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#define ESTCPU_MAX ((PRIO_MAX - 2) << ESTCPU_SHIFT)
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#define ESTCPU_ACCUM (1 << (ESTCPU_SHIFT - 1))
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#define ESTCPULIM(e) min((e), ESTCPU_MAX)
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/*
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* Constants for digital decay and forget:
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* 90% of (l_estcpu) usage in 5 * loadav time
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* 95% of (l_pctcpu) usage in 60 seconds (load insensitive)
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* Note that, as ps(1) mentions, this can let percentages
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* total over 100% (I've seen 137.9% for 3 processes).
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*
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* Note that hardclock updates l_estcpu and l_cpticks independently.
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*
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* We wish to decay away 90% of l_estcpu in (5 * loadavg) seconds.
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* That is, the system wants to compute a value of decay such
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* that the following for loop:
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* for (i = 0; i < (5 * loadavg); i++)
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* l_estcpu *= decay;
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* will compute
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* l_estcpu *= 0.1;
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* for all values of loadavg:
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*
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* Mathematically this loop can be expressed by saying:
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* decay ** (5 * loadavg) ~= .1
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*
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* The system computes decay as:
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* decay = (2 * loadavg) / (2 * loadavg + 1)
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*
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* We wish to prove that the system's computation of decay
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* will always fulfill the equation:
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* decay ** (5 * loadavg) ~= .1
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*
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* If we compute b as:
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* b = 2 * loadavg
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* then
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* decay = b / (b + 1)
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*
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* We now need to prove two things:
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* 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1)
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* 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg)
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*
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* Facts:
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* For x close to zero, exp(x) =~ 1 + x, since
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* exp(x) = 0! + x**1/1! + x**2/2! + ... .
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* therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b.
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* For x close to zero, ln(1+x) =~ x, since
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* ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1
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* therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1).
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* ln(.1) =~ -2.30
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*
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* Proof of (1):
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* Solve (factor)**(power) =~ .1 given power (5*loadav):
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* solving for factor,
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* ln(factor) =~ (-2.30/5*loadav), or
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* factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) =
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* exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED
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*
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* Proof of (2):
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* Solve (factor)**(power) =~ .1 given factor == (b/(b+1)):
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* solving for power,
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* power*ln(b/(b+1)) =~ -2.30, or
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* power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED
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*
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* Actual power values for the implemented algorithm are as follows:
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* loadav: 1 2 3 4
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* power: 5.68 10.32 14.94 19.55
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*/
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/* calculations for digital decay to forget 90% of usage in 5*loadav sec */
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#define loadfactor(loadav) (2 * (loadav))
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static fixpt_t
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decay_cpu(fixpt_t loadfac, fixpt_t estcpu)
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{
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if (estcpu == 0) {
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return 0;
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}
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#if !defined(_LP64)
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/* avoid 64bit arithmetics. */
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#define FIXPT_MAX ((fixpt_t)((UINTMAX_C(1) << sizeof(fixpt_t) * CHAR_BIT) - 1))
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if (__predict_true(loadfac <= FIXPT_MAX / ESTCPU_MAX)) {
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return estcpu * loadfac / (loadfac + FSCALE);
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}
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#endif /* !defined(_LP64) */
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return (uint64_t)estcpu * loadfac / (loadfac + FSCALE);
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}
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/*
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* For all load averages >= 1 and max l_estcpu of (255 << ESTCPU_SHIFT),
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* sleeping for at least seven times the loadfactor will decay l_estcpu to
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* less than (1 << ESTCPU_SHIFT).
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*
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* note that our ESTCPU_MAX is actually much smaller than (255 << ESTCPU_SHIFT).
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*/
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static fixpt_t
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decay_cpu_batch(fixpt_t loadfac, fixpt_t estcpu, unsigned int n)
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{
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if ((n << FSHIFT) >= 7 * loadfac) {
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return 0;
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}
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while (estcpu != 0 && n > 1) {
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estcpu = decay_cpu(loadfac, estcpu);
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n--;
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}
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return estcpu;
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}
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/*
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* sched_pstats_hook:
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*
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* Periodically called from sched_pstats(); used to recalculate priorities.
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*/
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void
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sched_pstats_hook(struct lwp *l, int batch)
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{
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fixpt_t loadfac;
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int sleeptm;
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/*
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* If the LWP has slept an entire second, stop recalculating
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* its priority until it wakes up.
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*/
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if (l->l_stat == LSSLEEP || l->l_stat == LSSTOP ||
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l->l_stat == LSSUSPENDED) {
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l->l_slptime++;
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sleeptm = 1;
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} else {
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sleeptm = 0x7fffffff;
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}
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if (l->l_slptime <= sleeptm) {
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loadfac = 2 * (averunnable.ldavg[0]);
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l->l_estcpu = decay_cpu(loadfac, l->l_estcpu);
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resetpriority(l);
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}
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}
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/*
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* Recalculate the priority of a process after it has slept for a while.
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*/
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static void
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updatepri(struct lwp *l)
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{
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fixpt_t loadfac;
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KASSERT(lwp_locked(l, NULL));
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KASSERT(l->l_slptime > 1);
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loadfac = loadfactor(averunnable.ldavg[0]);
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l->l_slptime--; /* the first time was done in sched_pstats */
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l->l_estcpu = decay_cpu_batch(loadfac, l->l_estcpu, l->l_slptime);
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resetpriority(l);
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}
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void
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sched_rqinit(void)
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{
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}
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void
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sched_setrunnable(struct lwp *l)
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{
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if (l->l_slptime > 1)
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updatepri(l);
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}
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void
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sched_nice(struct proc *p, int n)
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{
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struct lwp *l;
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KASSERT(mutex_owned(p->p_lock));
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p->p_nice = n;
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LIST_FOREACH(l, &p->p_lwps, l_sibling) {
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lwp_lock(l);
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resetpriority(l);
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lwp_unlock(l);
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}
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}
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/*
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* Recompute the priority of an LWP. Arrange to reschedule if
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* the resulting priority is better than that of the current LWP.
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*/
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static void
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resetpriority(struct lwp *l)
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{
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pri_t pri;
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struct proc *p = l->l_proc;
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KASSERT(lwp_locked(l, NULL));
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if (l->l_class != SCHED_OTHER)
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return;
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/* See comments above ESTCPU_SHIFT definition. */
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pri = (PRI_KERNEL - 1) - (l->l_estcpu >> ESTCPU_SHIFT) - p->p_nice;
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pri = imax(pri, 0);
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if (pri != l->l_priority)
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lwp_changepri(l, pri);
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}
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/*
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* We adjust the priority of the current process. The priority of a process
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* gets worse as it accumulates CPU time. The CPU usage estimator (l_estcpu)
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* is increased here. The formula for computing priorities (in kern_synch.c)
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* will compute a different value each time l_estcpu increases. This can
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* cause a switch, but unless the priority crosses a PPQ boundary the actual
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* queue will not change. The CPU usage estimator ramps up quite quickly
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* when the process is running (linearly), and decays away exponentially, at
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* a rate which is proportionally slower when the system is busy. The basic
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* principle is that the system will 90% forget that the process used a lot
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* of CPU time in 5 * loadav seconds. This causes the system to favor
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* processes which haven't run much recently, and to round-robin among other
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* processes.
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*/
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void
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sched_schedclock(struct lwp *l)
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{
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if (l->l_class != SCHED_OTHER)
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return;
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KASSERT(!CURCPU_IDLE_P());
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l->l_estcpu = ESTCPULIM(l->l_estcpu + ESTCPU_ACCUM);
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lwp_lock(l);
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resetpriority(l);
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lwp_unlock(l);
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}
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/*
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* sched_proc_fork:
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*
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* Inherit the parent's scheduler history.
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*/
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void
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sched_proc_fork(struct proc *parent, struct proc *child)
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{
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lwp_t *pl;
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KASSERT(mutex_owned(parent->p_lock));
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pl = LIST_FIRST(&parent->p_lwps);
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child->p_estcpu_inherited = pl->l_estcpu;
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child->p_forktime = sched_pstats_ticks;
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}
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/*
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* sched_proc_exit:
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*
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* Chargeback parents for the sins of their children.
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*/
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void
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sched_proc_exit(struct proc *parent, struct proc *child)
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{
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fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
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fixpt_t estcpu;
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lwp_t *pl, *cl;
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/* XXX Only if parent != init?? */
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mutex_enter(parent->p_lock);
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pl = LIST_FIRST(&parent->p_lwps);
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cl = LIST_FIRST(&child->p_lwps);
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estcpu = decay_cpu_batch(loadfac, child->p_estcpu_inherited,
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sched_pstats_ticks - child->p_forktime);
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if (cl->l_estcpu > estcpu) {
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lwp_lock(pl);
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pl->l_estcpu = ESTCPULIM(pl->l_estcpu + cl->l_estcpu - estcpu);
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lwp_unlock(pl);
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}
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mutex_exit(parent->p_lock);
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}
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void
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sched_wakeup(struct lwp *l)
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{
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}
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void
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sched_slept(struct lwp *l)
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{
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}
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void
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sched_lwp_fork(struct lwp *l1, struct lwp *l2)
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{
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l2->l_estcpu = l1->l_estcpu;
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}
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void
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sched_lwp_exit(struct lwp *l)
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{
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}
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void
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sched_lwp_collect(struct lwp *t)
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{
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lwp_t *l;
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/* Absorb estcpu value of collected LWP. */
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l = curlwp;
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lwp_lock(l);
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l->l_estcpu += t->l_estcpu;
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lwp_unlock(l);
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}
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void
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sched_oncpu(lwp_t *l)
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{
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}
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void
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sched_newts(lwp_t *l)
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{
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}
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/*
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* Sysctl nodes and initialization.
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|
*/
|
|
|
|
static int
|
|
sysctl_sched_rtts(SYSCTLFN_ARGS)
|
|
{
|
|
struct sysctlnode node;
|
|
int rttsms = hztoms(rrticks);
|
|
|
|
node = *rnode;
|
|
node.sysctl_data = &rttsms;
|
|
return sysctl_lookup(SYSCTLFN_CALL(&node));
|
|
}
|
|
|
|
SYSCTL_SETUP(sysctl_sched_4bsd_setup, "sysctl sched setup")
|
|
{
|
|
const struct sysctlnode *node = NULL;
|
|
|
|
sysctl_createv(clog, 0, NULL, NULL,
|
|
CTLFLAG_PERMANENT,
|
|
CTLTYPE_NODE, "kern", NULL,
|
|
NULL, 0, NULL, 0,
|
|
CTL_KERN, CTL_EOL);
|
|
sysctl_createv(clog, 0, NULL, &node,
|
|
CTLFLAG_PERMANENT,
|
|
CTLTYPE_NODE, "sched",
|
|
SYSCTL_DESCR("Scheduler options"),
|
|
NULL, 0, NULL, 0,
|
|
CTL_KERN, CTL_CREATE, CTL_EOL);
|
|
|
|
if (node == NULL)
|
|
return;
|
|
|
|
rrticks = hz / 10;
|
|
|
|
sysctl_createv(NULL, 0, &node, NULL,
|
|
CTLFLAG_PERMANENT,
|
|
CTLTYPE_STRING, "name", NULL,
|
|
NULL, 0, __UNCONST("4.4BSD"), 0,
|
|
CTL_CREATE, CTL_EOL);
|
|
sysctl_createv(NULL, 0, &node, NULL,
|
|
CTLFLAG_PERMANENT,
|
|
CTLTYPE_INT, "rtts",
|
|
SYSCTL_DESCR("Round-robin time quantum (in miliseconds)"),
|
|
sysctl_sched_rtts, 0, NULL, 0,
|
|
CTL_CREATE, CTL_EOL);
|
|
}
|