-rw-r--r-- 1260 libcpucycles-20230115/cpucycles/amd64-pmc.c raw
// version 20230105 // public domain // djb // adapted from supercop/cpucycles/amd64rdpmc.c #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include <sys/mman.h> #include <sys/syscall.h> #include <linux/perf_event.h> #include "cpucycles_internal.h" static struct perf_event_attr attr; static int fdperf = -1; static struct perf_event_mmap_page *buf = 0; long long ticks(void) { long long result; unsigned int seq; long long index; long long offset; do { seq = buf->lock; asm volatile("" ::: "memory"); index = buf->index; offset = buf->offset; asm volatile("rdpmc;shlq $32,%%rdx;orq %%rdx,%%rax" : "=a"(result) : "c"(index-1) : "%rdx"); asm volatile("" ::: "memory"); } while (buf->lock != seq); result += offset; result &= 0xffffffffffff; return result; } long long ticks_setup(void) { if (fdperf == -1) { attr.type = PERF_TYPE_HARDWARE; attr.config = PERF_COUNT_HW_CPU_CYCLES; attr.exclude_kernel = 1; fdperf = syscall(__NR_perf_event_open,&attr,0,-1,-1,0); if (fdperf == -1) return cpucycles_SKIP; buf = mmap(NULL,sysconf(_SC_PAGESIZE),PROT_READ,MAP_SHARED,fdperf,0); } if (!cpucycles_works(ticks)) return cpucycles_SKIP; return cpucycles_CYCLECOUNTER; }