timer.cc revision 12334 
1/*
2 * Copyright (c) 2012 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder.  You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions are
16 * met: redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer;
18 * redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution;
21 * neither the name of the copyright holders nor the names of its
22 * contributors may be used to endorse or promote products derived from
23 * this software without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 *
37 * Authors: Andreas Sandberg
38 */
39
40#include "cpu/kvm/timer.hh"
41
42#include <sys/syscall.h>
43#include <unistd.h>
44
45#include <algorithm>
46#include <csignal>
47#include <ctime>
48
49#include "base/logging.hh"
50#include "base/trace.hh"
51#include "debug/KvmTimer.hh"
52
53/* According to timer_create(2), the value SIGEV_THREAD_ID can be used
54 * to specify which thread a timer signal gets delivered to. According
55 * to the man page, the member sigev_notify_thread is used to specify
56 * the TID. This member is currently not defined by default in
57 * siginfo.h on x86, so we define it here as a workaround.
58 */
59#ifndef sigev_notify_thread_id
60#define sigev_notify_thread_id     _sigev_un._tid
61#endif
62
63static pid_t
64gettid()
65{
66    return syscall(__NR_gettid);
67}
68
69/**
70 * Minimum number of cycles that a host can spend in a KVM call (used
71 * to calculate the resolution of some timers).
72 *
73 * The value of this constant is a bit arbitrary, but in practice, we
74 * can't really do anything useful in less than ~1000 cycles.
75 */
76static const uint64_t MIN_HOST_CYCLES = 1000;
77
78PosixKvmTimer::PosixKvmTimer(int signo, clockid_t clockID,
79                             float hostFactor, Tick hostFreq)
80    : BaseKvmTimer(signo, hostFactor, hostFreq),
81      clockID(clockID)
82{
83    struct sigevent sev;
84
85    sev.sigev_notify = SIGEV_THREAD_ID;
86    sev.sigev_signo = signo;
87    sev.sigev_notify_thread_id = gettid();
88    sev.sigev_value.sival_ptr = NULL;
89
90    while (timer_create(clockID, &sev, &timer) == -1) {
91        if (errno != EAGAIN)
92            panic("timer_create: %i", errno);
93    }
94}
95
96PosixKvmTimer::~PosixKvmTimer()
97{
98    timer_delete(timer);
99}
100
101void
102PosixKvmTimer::arm(Tick ticks)
103{
104    struct itimerspec ts;
105    memset(&ts, 0, sizeof(ts));
106
107    ts.it_interval.tv_sec = 0;
108    ts.it_interval.tv_nsec = 0;
109    ts.it_value.tv_sec = hostNs(ticks) / 1000000000ULL;
110    ts.it_value.tv_nsec = hostNs(ticks) % 1000000000ULL;
111
112    assert(ts.it_value.tv_nsec > 0 || ts.it_value.tv_sec > 0);
113
114    DPRINTF(KvmTimer, "Arming POSIX timer: %i ticks (%is%ins)\n",
115            ticks, ts.it_value.tv_sec, ts.it_value.tv_nsec);
116
117    if (timer_settime(timer, 0, &ts, NULL) == -1)
118        panic("PosixKvmTimer: Failed to arm timer\n");
119}
120
121void
122PosixKvmTimer::disarm()
123{
124    struct itimerspec ts;
125    memset(&ts, 0, sizeof(ts));
126
127    DPRINTF(KvmTimer, "Disarming POSIX timer\n");
128
129    if (timer_settime(timer, 0, &ts, NULL) == -1)
130        panic("PosixKvmTimer: Failed to disarm timer\n");
131}
132
133Tick
134PosixKvmTimer::calcResolution()
135{
136    struct timespec ts;
137
138    if (clock_getres(clockID, &ts) == -1)
139        panic("PosixKvmTimer: Failed to get timer resolution\n");
140
141    const uint64_t res_ns(ts.tv_sec * 1000000000ULL + ts.tv_nsec);
142    // We preferrably want ticksFromHostNs() to calculate the the
143    // ceiling rather than truncating the value. However, there are
144    // other cases where truncating is fine, so we just add 1 here to
145    // make sure that the actual resolution is strictly less than what
146    // we return. We could get all kinds of nasty behavior if
147    // arm(resolution) is called and the resulting time is 0 (which
148    // could happen if we truncate the results and the resolution is
149    // 1ns).
150    const Tick resolution(ticksFromHostNs(res_ns) + 1);
151    // It might not make sense to enter into KVM for less than a
152    // certain number of host cycles. In some systems (e.g., Linux)
153    // the resolution of the timer we use is 1ns (a few cycles on most
154    // CPUs), which isn't very useful.
155    const Tick min_cycles(ticksFromHostCycles(MIN_HOST_CYCLES));
156
157    return std::max(resolution, min_cycles);
158}
159
160
161PerfKvmTimer::PerfKvmTimer(PerfKvmCounter &ctr,
162                           int signo, float hostFactor, Tick hostFreq)
163    : BaseKvmTimer(signo, hostFactor, hostFreq),
164      hwOverflow(ctr)
165{
166    hwOverflow.enableSignals(signo);
167}
168
169PerfKvmTimer::~PerfKvmTimer()
170{
171}
172
173void
174PerfKvmTimer::arm(Tick ticks)
175{
176    hwOverflow.period(hostCycles(ticks));
177    hwOverflow.refresh(1);
178}
179
180void
181PerfKvmTimer::disarm()
182{
183    hwOverflow.stop();
184}
185
186Tick
187PerfKvmTimer::calcResolution()
188{
189    return ticksFromHostCycles(MIN_HOST_CYCLES);
190}
191