c/c++ runner looping buffer#112
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graebm
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May 6, 2026
DmitriyMusatkin
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May 12, 2026
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crt-java appears to be benchmarking faster than the crt-c runner. Investigation shows that java is using a 8MiB buffer while native c is setting up one uber buffer the size of the file. Using a singular mega-buffer in crt-c was causing high CPU cache thrashing and accessing DRAM instead of utilizing faster CPU L3 cache.
This PR mirrors what Java is doing into the native C runner by setting up a fixed 8MiB buffer instead of a buffer sized to the largest upload file.
crt-c runner upload-max-throughput results:
With full file size buffer:
Gb/s mean: 147.25
Duration: 29.17
With 8MiB looping buffer:
Gb/s mean: 153.48
Duration: 27.99
crt-cpp runner was also updated as well.
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