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v2.x: Improve x86-64 timer performance #3748

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merged 2 commits into from
Jul 6, 2017
Merged

v2.x: Improve x86-64 timer performance #3748

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1aead8b
opal_progress: use usec native timer only when a native cycle counter…
matcabral Jun 23, 2017
37b30fa
x86_64 timers: use lfence instead of cpuid for serialization
matcabral Jun 23, 2017
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25 changes: 4 additions & 21 deletions opal/include/opal/sys/x86_64/timer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -31,31 +31,14 @@ typedef uint64_t opal_timer_t;

#if OPAL_GCC_INLINE_ASSEMBLY

/**
* http://www.intel.com/content/www/us/en/intelligent-systems/embedded-systems-training/ia-32-ia-64-benchmark-code-execution-paper.html
*/
/* TODO: add AMD mfence version and dispatch at init */
static inline opal_timer_t
opal_sys_timer_get_cycles(void)
{
unsigned l, h;
#if !OPAL_ASSEMBLY_SUPPORTS_RDTSCP
__asm__ __volatile__ ("cpuid\n\t"
uint32_t l, h;
__asm__ __volatile__ ("lfence\n\t"
"rdtsc\n\t"
: "=a" (l), "=d" (h)
:: "rbx", "rcx");
#else
/* If we need higher accuracy we should implement the algorithm proposed
* on the Intel document referenced above. However, in the context of MPI
* this function will be used as the backend for MPI_Wtime and as such
* can afford a small inaccuracy.
*/
__asm__ __volatile__ ("rdtscp\n\t"
"mov %%edx, %0\n\t"
"mov %%eax, %1\n\t"
"cpuid\n\t"
: "=r" (h), "=r" (l)
:: "rax", "rbx", "rcx", "rdx");
#endif
: "=a" (l), "=d" (h));
return ((opal_timer_t)l) | (((opal_timer_t)h) << 32);
}

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9 changes: 5 additions & 4 deletions opal/runtime/opal_progress.c
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,7 @@
#include "opal/runtime/opal_params.h"

#define OPAL_PROGRESS_USE_TIMERS (OPAL_TIMER_CYCLE_SUPPORTED || OPAL_TIMER_USEC_SUPPORTED)
#define OPAL_PROGRESS_ONLY_USEC_NATIVE (OPAL_TIMER_USEC_NATIVE && !OPAL_TIMER_CYCLE_NATIVE)

#if OPAL_ENABLE_DEBUG
bool opal_progress_debug = false;
Expand Down Expand Up @@ -193,11 +194,11 @@ opal_progress(void)
if( opal_progress_event_flag != 0 ) {
#if OPAL_HAVE_WORKING_EVENTOPS
#if OPAL_PROGRESS_USE_TIMERS
#if OPAL_TIMER_USEC_NATIVE
#if OPAL_PROGRESS_ONLY_USEC_NATIVE
opal_timer_t now = opal_timer_base_get_usec();
#else
opal_timer_t now = opal_timer_base_get_cycles();
#endif /* OPAL_TIMER_USEC_NATIVE */
#endif /* OPAL_PROGRESS_ONLY_USEC_NATIVE */
/* trip the event library if we've reached our tick rate and we are
enabled */
if (now - event_progress_last_time > event_progress_delta ) {
Expand Down Expand Up @@ -320,7 +321,7 @@ opal_progress_set_event_poll_rate(int polltime)

#if OPAL_PROGRESS_USE_TIMERS
event_progress_delta = 0;
# if OPAL_TIMER_USEC_NATIVE
# if OPAL_PROGRESS_ONLY_USEC_NATIVE
event_progress_last_time = opal_timer_base_get_usec();
# else
event_progress_last_time = opal_timer_base_get_cycles();
Expand All @@ -347,7 +348,7 @@ opal_progress_set_event_poll_rate(int polltime)
#endif
}

#if OPAL_PROGRESS_USE_TIMERS && !OPAL_TIMER_USEC_NATIVE
#if OPAL_PROGRESS_USE_TIMERS && !OPAL_PROGRESS_ONLY_USEC_NATIVE
/* going to use cycles for counter. Adjust specified usec into cycles */
event_progress_delta = event_progress_delta * opal_timer_base_get_freq() / 1000000;
#endif
Expand Down