First, add the SSD (or a partition in your SSD) as a cache device (enabling it to act as a cache device).
Then, ensure the kernel module parameter
l2arc_noprefetch is set to
FALSE, so that your streaming workloads are also put into the L2 ARC.
Every once in a while, remove it as a cache device, trim the SSD, and resume its usage as a cache device. This particular snippet of condensed truth will remain true until the SSD TRIM support gets into the ZFS on Linux tree.