Each resumable upload allocated a fresh chunk-sized buffer (8 MiB by
default, up to 64 MiB), so bulk transfers of large files churned
allocations and GC.
Buffer each chunk in a pool.RW from the global page pool instead so
the memory is reused across uploads and bounded by rclone's central
memory management.
The pool.RW is seekable, so the chunk is rewound at the start of each
retry rather than re-wrapped. lib/rest wraps request bodies in
readers.NoCloser so the transport cannot return the pages to the pool
between attempts - the Content-Length is set through rest.Opts because
the wrapped body is not a *bytes.Reader net/http can measure. A source
that runs dry before its declared size is reported as an unexpected EOF
rather than sending the short chunk.
Nick Craig-Wood
204f817100