zstd memory consumption kills nodes

[marten-seemann]

Running an IPFS node on a virtual server equipped with 2 GB of RAM leads to OOM within 2 - 5 minutes when qlog is running. The reason is that each zstd.Encoder consumes at least 8 MB of memory for an internal buffer, so just handling a little more than 200 QUIC connections simultaneously would consume all available memory.

I reported this to the zstd implementation in klauspost/compress#316.

I hope that this can be fixed there, otherwise we'd probably have to log the uncompressed qlog to disk first, and do the compression in a post-processing step when the respective connection is closed. This would reduce the number of simultaneously allocated zstd.Encoders.