Drazen Urch
7bd1550195
* Checkpoint * cpu cycle ffi * Rename * mixnode feature * Bundle libcpucycles
54 lines
1.2 KiB
C
54 lines
1.2 KiB
C
// version 20230105
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// public domain
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// djb
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// adapted from supercop/cpucycles/amd64rdpmc.c
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/mman.h>
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#include <sys/syscall.h>
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#include <linux/perf_event.h>
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#include "cpucycles_internal.h"
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static struct perf_event_attr attr;
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static int fdperf = -1;
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static struct perf_event_mmap_page *buf = 0;
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long long ticks(void)
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{
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long long result;
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unsigned int seq;
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long long index;
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long long offset;
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do {
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seq = buf->lock;
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asm volatile("" ::: "memory");
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index = buf->index;
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offset = buf->offset;
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asm volatile("rdpmc;shlq $32,%%rdx;orq %%rdx,%%rax"
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: "=a"(result) : "c"(index-1) : "%rdx");
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asm volatile("" ::: "memory");
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} while (buf->lock != seq);
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result += offset;
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result &= 0xffffffffffff;
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return result;
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}
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long long ticks_setup(void)
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{
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if (fdperf == -1) {
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attr.type = PERF_TYPE_HARDWARE;
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attr.config = PERF_COUNT_HW_CPU_CYCLES;
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attr.exclude_kernel = 1;
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fdperf = syscall(__NR_perf_event_open,&attr,0,-1,-1,0);
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if (fdperf == -1) return cpucycles_SKIP;
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buf = mmap(NULL,sysconf(_SC_PAGESIZE),PROT_READ,MAP_SHARED,fdperf,0);
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}
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if (!cpucycles_works(ticks)) return cpucycles_SKIP;
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return cpucycles_CYCLECOUNTER;
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}
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