timer.cc revision 10073 
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 <algorithm>
41#include <csignal>
42#include <ctime>
43#include <unistd.h>
44#include <sys/syscall.h>
45
46#include "base/misc.hh"
47#include "base/trace.hh"
48#include "cpu/kvm/timer.hh"
49#include "debug/KvmTimer.hh"
50
51/* According to timer_create(2), the value SIGEV_THREAD_ID can be used
52 * to specify which thread a timer signal gets delivered to. According
53 * to the man page, the member sigev_notify_thread is used to specify
54 * the TID. This member is currently not defined by default in
55 * siginfo.h on x86, so we define it here as a workaround.
56 */
57#ifndef sigev_notify_thread_id
58#define sigev_notify_thread_id     _sigev_un._tid
59#endif
60
61static pid_t
62gettid()
63{
64    return syscall(__NR_gettid);
65}
66
67/**
68 * Minimum number of cycles that a host can spend in a KVM call (used
69 * to calculate the resolution of some timers).
70 *
71 * The value of this constant is a bit arbitrary, but in practice, we
72 * can't really do anything useful in less than ~1000 cycles.
73 */
74static const uint64_t MIN_HOST_CYCLES = 1000;
75
76PosixKvmTimer::PosixKvmTimer(int signo, clockid_t clockID,
77                             float hostFactor, Tick hostFreq)
78    : BaseKvmTimer(signo, hostFactor, hostFreq),
79      clockID(clockID)
80{
81    struct sigevent sev;
82
83    sev.sigev_notify = SIGEV_THREAD_ID;
84    sev.sigev_signo = signo;
85    sev.sigev_notify_thread_id = gettid();
86    sev.sigev_value.sival_ptr = NULL;
87
88    while (timer_create(clockID, &sev, &timer) == -1) {
89        if (errno != EAGAIN)
90            panic("timer_create: %i", errno);
91    }
92}
93
94PosixKvmTimer::~PosixKvmTimer()
95{
96    timer_delete(timer);
97}
98
99void
100PosixKvmTimer::arm(Tick ticks)
101{
102    struct itimerspec ts;
103    memset(&ts, 0, sizeof(ts));
104
105    ts.it_interval.tv_sec = 0;
106    ts.it_interval.tv_nsec = 0;
107    ts.it_value.tv_sec = hostNs(ticks) / 1000000000ULL;
108    ts.it_value.tv_nsec = hostNs(ticks) % 1000000000ULL;
109
110    assert(ts.it_value.tv_nsec > 0 || ts.it_value.tv_sec > 0);
111
112    DPRINTF(KvmTimer, "Arming POSIX timer: %i ticks (%is%ins)\n",
113            ticks, ts.it_value.tv_sec, ts.it_value.tv_nsec);
114
115    if (timer_settime(timer, 0, &ts, NULL) == -1)
116        panic("PosixKvmTimer: Failed to arm timer\n");
117}
118
119void
120PosixKvmTimer::disarm()
121{
122    struct itimerspec ts;
123    memset(&ts, 0, sizeof(ts));
124
125    DPRINTF(KvmTimer, "Disarming POSIX timer\n");
126
127    if (timer_settime(timer, 0, &ts, NULL) == -1)
128        panic("PosixKvmTimer: Failed to disarm timer\n");
129}
130
131Tick
132PosixKvmTimer::calcResolution()
133{
134    struct timespec ts;
135
136    if (clock_getres(clockID, &ts) == -1)
137        panic("PosixKvmTimer: Failed to get timer resolution\n");
138
139    const uint64_t res_ns(ts.tv_sec * 1000000000ULL + ts.tv_nsec);
140    // We preferrably want ticksFromHostNs() to calculate the the
141    // ceiling rather than truncating the value. However, there are
142    // other cases where truncating is fine, so we just add 1 here to
143    // make sure that the actual resolution is strictly less than what
144    // we return. We could get all kinds of nasty behavior if
145    // arm(resolution) is called and the resulting time is 0 (which
146    // could happen if we truncate the results and the resolution is
147    // 1ns).
148    const Tick resolution(ticksFromHostNs(res_ns) + 1);
149    // It might not make sense to enter into KVM for less than a
150    // certain number of host cycles. In some systems (e.g., Linux)
151    // the resolution of the timer we use is 1ns (a few cycles on most
152    // CPUs), which isn't very useful.
153    const Tick min_cycles(ticksFromHostCycles(MIN_HOST_CYCLES));
154
155    return std::max(resolution, min_cycles);
156}
157
158
159PerfKvmTimer::PerfKvmTimer(PerfKvmCounter &ctr,
160                           int signo, float hostFactor, Tick hostFreq)
161    : BaseKvmTimer(signo, hostFactor, hostFreq),
162      hwOverflow(ctr)
163{
164    hwOverflow.enableSignals(signo);
165}
166
167PerfKvmTimer::~PerfKvmTimer()
168{
169}
170
171void
172PerfKvmTimer::arm(Tick ticks)
173{
174    hwOverflow.period(hostCycles(ticks));
175    hwOverflow.refresh(1);
176}
177
178void
179PerfKvmTimer::disarm()
180{
181    hwOverflow.stop();
182}
183
184Tick
185PerfKvmTimer::calcResolution()
186{
187    return ticksFromHostCycles(MIN_HOST_CYCLES);
188}
189