In v1.63 memory usage in the b2 backend was limited to `--transfers` *
`--b2-chunk-size`
However in v1.64 this was raised to `--transfers` * `--b2-chunk-size`
* `--b2-upload-concurrency`.
The default value for this was accidently set quite high at 16 which
means by default rclone could use up to 6.4GB of memory!
The new default sets a more reasonable (but still high) max memory of 1.6GB.
Nick Craig-Wood
cb43e86d16