Rss memory leak

[twoeths]

There is a rss memory leak issue found from ChainSafe/lodestar#4623

to reproduce:

import {ssz} from "@lodestar/types";
import snappy from "@chainsafe/snappy-stream";

// could be any data
const singleBlockBytes = ssz.bellatrix.SignedBeaconBlock.serialize(ssz.bellatrix.SignedBeaconBlock.defaultValue());

async function memTest(): Promise<void> {
  const count = 1_000_000_000;
  for (let i = 0; i < count; i++) {
    const stream = snappy.createCompressStream();
    stream.write(singleBlockBytes);
    stream.end();
    if (i % 100_000 === 0) {
      await new Promise((resolve) => setTimeout(resolve, 100));
      const {heapTotal, rss} = process.memoryUsage();
      console.log(
        "Memory usage",
        Math.floor((i * 100) / count) + "%",
        "heapTotal",
        toMem(heapTotal),
        "rss",
        toMem(rss)
      );
    }
  }
}

some output

Memory usage 4% heapTotal +384.67 MB rss +5.01 GB
Memory usage 4% heapTotal +565.29 MB rss +5.3 GB
Memory usage 4% heapTotal +745.65 MB rss +5.56 GB
Memory usage 4% heapTotal +932.56 MB rss +5.65 GB
Memory usage 4% heapTotal +1.11 GB rss +5.78 GB
Memory usage 4% heapTotal +409.32 MB rss +4.99 GB
Memory usage 4% heapTotal +563.2 MB rss +5.25 GB

heap total is not leaked but rss keeps increasing, it seems "@chainsafe/fast-crc32c" is the root cause