87 lines
4.2 KiB
C
87 lines
4.2 KiB
C
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#include <stdio.h>
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#include <stdlib.h>
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int main() {
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// Actual benchmark results
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double measured_hakmem_100k = 4.9; // MB
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double measured_hakmem_1M = 39.6; // MB
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double measured_mimalloc_100k = 5.1;
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double measured_mimalloc_1M = 25.1;
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// Theoretical data
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double data_100k = 100000 * 16.0 / (1024*1024); // 1.53 MB
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double data_1M = 1000000 * 16.0 / (1024*1024); // 15.26 MB
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printf("=== SCALING ANALYSIS ===\n\n");
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printf("100K allocations (%.2f MB data):\n", data_100k);
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printf(" HAKMEM: %.2f MB (%.0f%% overhead)\n",
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measured_hakmem_100k, (measured_hakmem_100k/data_100k - 1)*100);
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printf(" mimalloc: %.2f MB (%.0f%% overhead)\n\n",
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measured_mimalloc_100k, (measured_mimalloc_100k/data_100k - 1)*100);
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printf("1M allocations (%.2f MB data):\n", data_1M);
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printf(" HAKMEM: %.2f MB (%.0f%% overhead)\n",
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measured_hakmem_1M, (measured_hakmem_1M/data_1M - 1)*100);
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printf(" mimalloc: %.2f MB (%.0f%% overhead)\n\n",
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measured_mimalloc_1M, (measured_mimalloc_1M/data_1M - 1)*100);
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printf("=== THE PARADOX ===\n\n");
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// Calculate per-allocation overhead
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double hakmem_per_alloc_100k = (measured_hakmem_100k - data_100k) * 1024 * 1024 / 100000;
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double hakmem_per_alloc_1M = (measured_hakmem_1M - data_1M) * 1024 * 1024 / 1000000;
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double mimalloc_per_alloc_100k = (measured_mimalloc_100k - data_100k) * 1024 * 1024 / 100000;
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double mimalloc_per_alloc_1M = (measured_mimalloc_1M - data_1M) * 1024 * 1024 / 1000000;
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printf("Per-allocation overhead:\n");
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printf(" HAKMEM 100K: %.1f bytes/alloc\n", hakmem_per_alloc_100k);
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printf(" HAKMEM 1M: %.1f bytes/alloc\n", hakmem_per_alloc_1M);
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printf(" mimalloc 100K: %.1f bytes/alloc\n", mimalloc_per_alloc_100k);
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printf(" mimalloc 1M: %.1f bytes/alloc\n\n", mimalloc_per_alloc_1M);
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// Calculate fixed overhead
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// Formula: measured = data + fixed + (per_alloc * N)
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// measured_100k = data_100k + fixed + per_alloc * 100k
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// measured_1M = data_1M + fixed + per_alloc * 1M
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// Solve for fixed and per_alloc
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// Assume per_alloc is constant
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double delta_measured_hakmem = measured_hakmem_1M - measured_hakmem_100k;
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double delta_data = data_1M - data_100k;
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double delta_allocs = 900000;
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double hakmem_per_alloc = (delta_measured_hakmem - delta_data) * 1024 * 1024 / delta_allocs;
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double hakmem_fixed = (measured_hakmem_100k - data_100k) * 1024 * 1024 - hakmem_per_alloc * 100000;
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double delta_measured_mimalloc = measured_mimalloc_1M - measured_mimalloc_100k;
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double mimalloc_per_alloc = (delta_measured_mimalloc - delta_data) * 1024 * 1024 / delta_allocs;
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double mimalloc_fixed = (measured_mimalloc_100k - data_100k) * 1024 * 1024 - mimalloc_per_alloc * 100000;
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printf("=== COST MODEL ===\n");
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printf("Formula: Total = Data + Fixed + (PerAlloc × N)\n\n");
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printf("HAKMEM:\n");
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printf(" Fixed overhead: %.2f MB\n", hakmem_fixed / (1024*1024));
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printf(" Per-alloc overhead: %.1f bytes\n", hakmem_per_alloc);
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printf(" At 100K: %.2f = %.2f + %.2f + (%.1f × 100K)\n",
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measured_hakmem_100k, data_100k, hakmem_fixed/(1024*1024), hakmem_per_alloc);
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printf(" At 1M: %.2f = %.2f + %.2f + (%.1f × 1M)\n\n",
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measured_hakmem_1M, data_1M, hakmem_fixed/(1024*1024), hakmem_per_alloc);
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printf("mimalloc:\n");
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printf(" Fixed overhead: %.2f MB\n", mimalloc_fixed / (1024*1024));
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printf(" Per-alloc overhead: %.1f bytes\n", mimalloc_per_alloc);
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printf(" At 100K: %.2f = %.2f + %.2f + (%.1f × 100K)\n",
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measured_mimalloc_100k, data_100k, mimalloc_fixed/(1024*1024), mimalloc_per_alloc);
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printf(" At 1M: %.2f = %.2f + %.2f + (%.1f × 1M)\n\n",
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measured_mimalloc_1M, data_1M, mimalloc_fixed/(1024*1024), mimalloc_per_alloc);
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printf("=== KEY INSIGHT ===\n");
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printf("HAKMEM has %.1f× HIGHER per-allocation overhead (%.1f vs %.1f bytes)\n",
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hakmem_per_alloc / mimalloc_per_alloc, hakmem_per_alloc, mimalloc_per_alloc);
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printf("This means: Bitmap metadata is NOT 0.125 bytes/block as expected!\n");
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return 0;
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}
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