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/*
* Copyright (c) 2012 ARM Limited
* All rights reserved
*
* The license below extends only to copyright in the software and shall
* not be construed as granting a license to any other intellectual
* property including but not limited to intellectual property relating
* to a hardware implementation of the functionality of the software
* licensed hereunder. You may use the software subject to the license
* terms below provided that you ensure that this notice is replicated
* unmodified and in its entirety in all distributions of the software,
* modified or unmodified, in source code or in binary form.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Andreas Sandberg
*/
#include "cpu/kvm/timer.hh"
#include <sys/syscall.h>
#include <unistd.h>
#include <algorithm>
#include <csignal>
#include <ctime>
#include "base/logging.hh"
#include "base/trace.hh"
#include "debug/KvmTimer.hh"
/* According to timer_create(2), the value SIGEV_THREAD_ID can be used
* to specify which thread a timer signal gets delivered to. According
* to the man page, the member sigev_notify_thread is used to specify
* the TID. This member is currently not defined by default in
* siginfo.h on x86, so we define it here as a workaround.
*/
#ifndef sigev_notify_thread_id
#define sigev_notify_thread_id _sigev_un._tid
#endif
static pid_t
gettid()
{
return syscall(__NR_gettid);
}
/**
* Minimum number of cycles that a host can spend in a KVM call (used
* to calculate the resolution of some timers).
*
* The value of this constant is a bit arbitrary, but in practice, we
* can't really do anything useful in less than ~1000 cycles.
*/
static const uint64_t MIN_HOST_CYCLES = 1000;
PosixKvmTimer::PosixKvmTimer(int signo, clockid_t clockID,
float hostFactor, Tick hostFreq)
: BaseKvmTimer(signo, hostFactor, hostFreq),
clockID(clockID)
{
struct sigevent sev;
sev.sigev_notify = SIGEV_THREAD_ID;
sev.sigev_signo = signo;
sev.sigev_notify_thread_id = gettid();
sev.sigev_value.sival_ptr = NULL;
while (timer_create(clockID, &sev, &timer) == -1) {
if (errno != EAGAIN)
panic("timer_create: %i", errno);
}
}
PosixKvmTimer::~PosixKvmTimer()
{
timer_delete(timer);
}
void
PosixKvmTimer::arm(Tick ticks)
{
struct itimerspec ts;
memset(&ts, 0, sizeof(ts));
ts.it_interval.tv_sec = 0;
ts.it_interval.tv_nsec = 0;
ts.it_value.tv_sec = hostNs(ticks) / 1000000000ULL;
ts.it_value.tv_nsec = hostNs(ticks) % 1000000000ULL;
assert(ts.it_value.tv_nsec > 0 || ts.it_value.tv_sec > 0);
DPRINTF(KvmTimer, "Arming POSIX timer: %i ticks (%is%ins)\n",
ticks, ts.it_value.tv_sec, ts.it_value.tv_nsec);
if (timer_settime(timer, 0, &ts, NULL) == -1)
panic("PosixKvmTimer: Failed to arm timer\n");
}
void
PosixKvmTimer::disarm()
{
struct itimerspec ts;
memset(&ts, 0, sizeof(ts));
DPRINTF(KvmTimer, "Disarming POSIX timer\n");
if (timer_settime(timer, 0, &ts, NULL) == -1)
panic("PosixKvmTimer: Failed to disarm timer\n");
}
Tick
PosixKvmTimer::calcResolution()
{
struct timespec ts;
if (clock_getres(clockID, &ts) == -1)
panic("PosixKvmTimer: Failed to get timer resolution\n");
const uint64_t res_ns(ts.tv_sec * 1000000000ULL + ts.tv_nsec);
// We preferrably want ticksFromHostNs() to calculate the the
// ceiling rather than truncating the value. However, there are
// other cases where truncating is fine, so we just add 1 here to
// make sure that the actual resolution is strictly less than what
// we return. We could get all kinds of nasty behavior if
// arm(resolution) is called and the resulting time is 0 (which
// could happen if we truncate the results and the resolution is
// 1ns).
const Tick resolution(ticksFromHostNs(res_ns) + 1);
// It might not make sense to enter into KVM for less than a
// certain number of host cycles. In some systems (e.g., Linux)
// the resolution of the timer we use is 1ns (a few cycles on most
// CPUs), which isn't very useful.
const Tick min_cycles(ticksFromHostCycles(MIN_HOST_CYCLES));
return std::max(resolution, min_cycles);
}
PerfKvmTimer::PerfKvmTimer(PerfKvmCounter &ctr,
int signo, float hostFactor, Tick hostFreq)
: BaseKvmTimer(signo, hostFactor, hostFreq),
hwOverflow(ctr)
{
hwOverflow.enableSignals(signo);
}
PerfKvmTimer::~PerfKvmTimer()
{
}
void
PerfKvmTimer::arm(Tick ticks)
{
hwOverflow.period(hostCycles(ticks));
hwOverflow.refresh(1);
}
void
PerfKvmTimer::disarm()
{
hwOverflow.stop();
}
Tick
PerfKvmTimer::calcResolution()
{
return ticksFromHostCycles(MIN_HOST_CYCLES);
}
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