add unaligned load penalty tests
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src/12_unaligned_load_penalties/cyclic_load_bytes.asm
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27
src/12_unaligned_load_penalties/cyclic_load_bytes.asm
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global cyclic_load_bytes
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section .text
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; rdi - buffer
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; rsi - inner_loop_count
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; rdx - outer_loop_count
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cyclic_load_bytes:
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xor r8, r8
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.outer_loop:
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mov rcx, rdi
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xor r9, r9
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.inner_loop:
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vmovdqu ymm0, [rcx]
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vmovdqu ymm0, [rcx + 32]
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vmovdqu ymm0, [rcx + 64]
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vmovdqu ymm0, [rcx + 96]
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add rcx, 128
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add r9, 128
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cmp r9, rsi
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jb .inner_loop
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inc r8
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cmp r8, rdx
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jb .outer_loop
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ret
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3
src/12_unaligned_load_penalties/cyclic_load_bytes.h
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3
src/12_unaligned_load_penalties/cyclic_load_bytes.h
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#include <stdint.h>
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void cyclic_load_bytes(uint8_t *buffer, uint64_t inner_loop_count, uint64_t outer_loop_count);
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src/12_unaligned_load_penalties/main.c
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src/12_unaligned_load_penalties/main.c
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#include "repetition_tester.c"
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#include "cyclic_load_bytes.h"
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#include <sys/mman.h>
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static uint64_t kibibytes(uint64_t count) {
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return 1024 * count;
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}
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static uint64_t mibibytes(uint64_t count) {
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return 1024 * kibibytes(count);
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}
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static uint64_t gibibytes(uint64_t count) {
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return 1024 * mibibytes(count);
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}
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int main() {
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// uint32_t byte_counts[] = { kibibytes(16), kibibytes(64), mibibytes(1) };
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uint32_t byte_counts[] = { mibibytes(1) };
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uint64_t offsets[] = { 0, 1, 2, 4, 8, 16, 32, 64 };
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struct repetitor repetitor = {};
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repetitor_init(&repetitor);
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printf("CPU Frequency: %ldHz (~%.2fGHz)\n", repetitor.cpu_freq, (float)repetitor.cpu_freq/(1000*1000*1000));
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uint64_t buffer_size = gibibytes(1);
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if (buffer_size % 4096) {
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printf("ERROR: Size of buffer is not page aligned\n");
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return -1;
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}
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uint8_t *buffer = mmap(0, buffer_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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if (buffer == NULL) {
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printf("ERROR: Failed to allocate buffer\n");
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return -1;
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}
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if ((size_t)buffer % 64 != 0) {
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printf("ERROR: Allocated buffer is not cache line aligned, it is %ld\n", (size_t)buffer % 64);
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return -1;
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}
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// Touch pages so they would be mapped in, to avoid page faults during tests
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for (uint64_t i = 0; i < buffer_size; i += 4096) {
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buffer[i] = (uint8_t)i;
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}
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for (int i = 0; i < ARRAY_LEN(byte_counts); i++) {
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uint64_t unadjusted_byte_count = byte_counts[i];
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assert(unadjusted_byte_count % 128 == 0); // Must be divisible by 128
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uint64_t byte_count = unadjusted_byte_count - 128;
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for (int j = 0; j < ARRAY_LEN(offsets); j++) {
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uint64_t offset = offsets[j];
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uint64_t outer_loop_count = buffer_size / byte_count;
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uint64_t bytes_read = outer_loop_count * byte_count;
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repetitor_clear(&repetitor);
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while (repetitor_repeat(&repetitor, 5)) {
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repetitor_start(&repetitor);
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repetitor_measure_start(&repetitor);
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cyclic_load_bytes(buffer + offset, byte_count, outer_loop_count);
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repetitor_measure_stop(&repetitor, bytes_read);
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repetitor_stop(&repetitor);
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}
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char name[128] = { 0 };
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snprintf(name, sizeof(name), "%ld offset, %ld size", offset, byte_count);
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repetitor_print_results_label(&repetitor, name);
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}
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}
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munmap(buffer, buffer_size);
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return 0;
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}
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