mirror/tracy
1
0
Fork 0
mirror of https://github.com/wolfpld/tracy.git synced 2024-11-10 02:31:48 +00:00
Code Issues Packages Projects Releases Wiki Activity

Degrade ARM timer to monotonic raw clock.

Browse Source 
The monotonic raw clock has the same accuracy as reading cntvct registers, but
using clock_gettime() has a measurable impact on queueing time (135 us vs
83 us).

This change is needed to enable ftrace time readings on ARM linux, which
doesn't provide any way to get raw cntvct readings, like x86-tsc on x86.
This commit is contained in:
Bartosz Taudul 2019-08-14 16:19:02 +02:00
parent 42865d7c7b
commit 5fbb811f5d
2 changed files with 12 additions and 105 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

103
client/TracyProfiler.cpp
View File

@ -151,89 +151,7 @@ struct ThreadHandleWrapper
#endif
#if defined TRACY_HW_TIMER && __ARM_ARCH >= 6 && !defined TARGET_OS_IOS
int64_t (*GetTimeImpl)();
int64_t GetTimeImplFallback()
{
# ifdef CLOCK_MONOTONIC_RAW
struct timespec ts;
clock_gettime( CLOCK_MONOTONIC_RAW, &ts );
return int64_t( ts.tv_sec ) * 1000000000 + int64_t( ts.tv_nsec );
# else
return std::chrono::duration_cast<std::chrono::nanoseconds>( std::chrono::high_resolution_clock::now().time_since_epoch() ).count();
# endif
}
int64_t GetTimeImplCntvct()
{
int64_t t;
# ifdef __aarch64__
asm volatile ( "mrs %0, cntvct_el0" : "=r" (t) );
# else
asm volatile ( "mrrc p15, 1, %Q0, %R0, c14" : "=r" (t) );
# endif
return t;
}
static sigjmp_buf SigIllEnv;
static int SetupHwTimerFailed()
{
return sigsetjmp( SigIllEnv, 1 );
}
static void SetupHwTimerSigIllHandler( int /*signum*/ )
{
siglongjmp( SigIllEnv, 1 );
}
static int64_t SetupHwTimer()
{
struct sigaction act, oldact;
memset( &act, 0, sizeof( act ) );
act.sa_handler = SetupHwTimerSigIllHandler;
if( sigaction( SIGILL, &act, &oldact ) )
{
GetTimeImpl = GetTimeImplFallback;
return Profiler::GetTime();
}
if( SetupHwTimerFailed() )
{
sigaction( SIGILL, &oldact, nullptr );
GetTimeImpl = GetTimeImplFallback;
return Profiler::GetTime();
}
GetTimeImplCntvct();
sigaction( SIGILL, &oldact, nullptr );
GetTimeImpl = GetTimeImplCntvct;
// Check if cntvct is monotonic (there is faulty hw out there)
enum { NumProbes = 32 * 1024 };
int64_t probe[NumProbes];
for( int j=0; j<10; j++ )
{
for( int i=0; i<NumProbes; i++ )
{
probe[i] = Profiler::GetTime();
}
for( int i=1; i<NumProbes; i++ )
{
if( probe[i] < probe[i-1] )
{
GetTimeImpl = GetTimeImplFallback;
return Profiler::GetTime();
}
}
}
return Profiler::GetTime();
}
#elif defined TRACY_HW_TIMER && ( defined __i386 || defined _M_IX86 || defined __x86_64__ || defined _M_X64 )
#if defined TRACY_HW_TIMER && ( defined __i386 || defined _M_IX86 || defined __x86_64__ || defined _M_X64 )
static inline void CpuId( uint32_t* regs, uint32_t leaf )
{
#if defined _WIN32 || defined __CYGWIN__
@ -2141,24 +2059,12 @@ void Profiler::HandleDisconnect()
}
}
bool Profiler::IsTimerMonotonicRaw()
{
#if defined TRACY_HW_TIMER && !defined TARGET_OS_IOS && __ARM_ARCH >= 6
return GetTimeImpl == GetTimeImplFallback;
#else
return false;
#endif
}
void Profiler::CalibrateTimer()
{
#ifdef TRACY_HW_TIMER
if( IsTimerMonotonicRaw() )
{
m_timerMul = 1.;
return;
}
# if !defined TARGET_OS_IOS && __ARM_ARCH >= 6
m_timerMul = 1.;
# else
std::atomic_signal_fence( std::memory_order_acq_rel );
const auto t0 = std::chrono::high_resolution_clock::now();
const auto r0 = GetTime();
@ -2173,6 +2079,7 @@ void Profiler::CalibrateTimer()
const auto dr = r1 - r0;
m_timerMul = double( dt ) / double( dr );
# endif
#else
m_timerMul = 1.;
#endif

14
client/TracyProfiler.hpp
View File

@ -78,10 +78,6 @@ struct LuaZoneState
using Magic = moodycamel::ConcurrentQueueDefaultTraits::index_t;
#if __ARM_ARCH >= 6 && !defined TARGET_OS_IOS
extern int64_t (*GetTimeImpl)();
#endif
class Profiler
{
@ -105,7 +101,13 @@ public:
# if TARGET_OS_IOS == 1
return mach_absolute_time();
# elif __ARM_ARCH >= 6
return GetTimeImpl();
# ifdef CLOCK_MONOTONIC_RAW
struct timespec ts;
clock_gettime( CLOCK_MONOTONIC_RAW, &ts );
return int64_t( ts.tv_sec ) * 1000000000ll + int64_t( ts.tv_nsec );
# else
return std::chrono::duration_cast<std::chrono::nanoseconds>( std::chrono::high_resolution_clock::now().time_since_epoch() ).count();
# endif
# elif defined _WIN32 || defined __CYGWIN__
unsigned int dontcare;
const auto t = int64_t( __rdtscp( &dontcare ) );
@ -440,8 +442,6 @@ public:
void RequestShutdown() { m_shutdown.store( true, std::memory_order_relaxed ); m_shutdownManual.store( true, std::memory_order_relaxed ); }
bool HasShutdownFinished() const { return m_shutdownFinished.load( std::memory_order_relaxed ); }
static bool IsTimerMonotonicRaw();
private:
enum class DequeueStatus { Success, ConnectionLost, QueueEmpty };