2 * Copyright (c) 2012 ARM Limited
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38 #include "cpu/kvm/timer.hh"
40 #include <sys/syscall.h>
47 #include "base/logging.hh"
48 #include "base/trace.hh"
49 #include "debug/KvmTimer.hh"
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.
57 #ifndef sigev_notify_thread_id
58 #define sigev_notify_thread_id _sigev_un._tid
64 return syscall(__NR_gettid
);
68 * Minimum number of cycles that a host can spend in a KVM call (used
69 * to calculate the resolution of some timers).
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.
74 static const uint64_t MIN_HOST_CYCLES
= 1000;
76 PosixKvmTimer::PosixKvmTimer(int signo
, clockid_t clockID
,
77 float hostFactor
, Tick hostFreq
)
78 : BaseKvmTimer(signo
, hostFactor
, hostFreq
),
83 sev
.sigev_notify
= SIGEV_THREAD_ID
;
84 sev
.sigev_signo
= signo
;
85 sev
.sigev_notify_thread_id
= sysGettid();
86 sev
.sigev_value
.sival_ptr
= NULL
;
88 while (timer_create(clockID
, &sev
, &timer
) == -1) {
90 panic("timer_create: %i", errno
);
94 PosixKvmTimer::~PosixKvmTimer()
100 PosixKvmTimer::arm(Tick ticks
)
102 struct itimerspec ts
;
103 memset(&ts
, 0, sizeof(ts
));
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;
110 assert(ts
.it_value
.tv_nsec
> 0 || ts
.it_value
.tv_sec
> 0);
112 DPRINTF(KvmTimer
, "Arming POSIX timer: %i ticks (%is%ins)\n",
113 ticks
, ts
.it_value
.tv_sec
, ts
.it_value
.tv_nsec
);
115 if (timer_settime(timer
, 0, &ts
, NULL
) == -1)
116 panic("PosixKvmTimer: Failed to arm timer\n");
120 PosixKvmTimer::disarm()
122 struct itimerspec ts
;
123 memset(&ts
, 0, sizeof(ts
));
125 DPRINTF(KvmTimer
, "Disarming POSIX timer\n");
127 if (timer_settime(timer
, 0, &ts
, NULL
) == -1)
128 panic("PosixKvmTimer: Failed to disarm timer\n");
132 PosixKvmTimer::calcResolution()
136 if (clock_getres(clockID
, &ts
) == -1)
137 panic("PosixKvmTimer: Failed to get timer resolution\n");
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
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
));
155 return std::max(resolution
, min_cycles
);
159 PerfKvmTimer::PerfKvmTimer(PerfKvmCounter
&ctr
,
160 int signo
, float hostFactor
, Tick hostFreq
)
161 : BaseKvmTimer(signo
, hostFactor
, hostFreq
),
164 hwOverflow
.enableSignals(signo
);
167 PerfKvmTimer::~PerfKvmTimer()
172 PerfKvmTimer::arm(Tick ticks
)
174 hwOverflow
.period(hostCycles(ticks
));
175 hwOverflow
.refresh(1);
179 PerfKvmTimer::disarm()
185 PerfKvmTimer::calcResolution()
187 return ticksFromHostCycles(MIN_HOST_CYCLES
);