These are some results of the optimizations for the memory subsystem. Of course, more feedback is needed and always welcome!
System under normal load (large adblock list, samba4, minidlna)
Gathering stats info for zswap subsystem
ZSWAP
-----
Compressor - lz4hc
zmalloc zpool - z3fold
Memory pool - 18.00 %
STATS
-----
Pool total size - 15.95 MiB
Original data size - 44.93 MiB
Estimated savings - 28.97 MiB
Written back pages - 0
Stored (cached) pages - 11501
Uncompressible pages - 4
Compression ratio - 2.82
Gathering stats info for zram device "zram0"
ZRAM
----
Block device - /sys/block/zram0
Device size - 185 MiB
Compression algo - lzo lz4 lz4hc [zstd]
Compression streams - 4
DATA
----
Original data size - 1.80 MiB
Compressed data size - 1.58 MiB
Estimated savings - 0.22 MiB
Compression ratio - 1.14
Expected c. ratio - 4.25
MEMORY
------
Memory used, total - 1.63 MiB
Allocator overhead - 0.05 MiB
Allocator efficiency - 96.71 %
Maximum memory ever used - 1.79 MiB
Memory limit - 43.53 MiB
PAGES
-----
Same pages count - 0
Pages compacted - 0
Free pages discarded - 114232
System after forced load
stress --vm 4 --vm-bytes 250M --timeout 10s
Gathering stats info for zswap subsystem
ZSWAP
-----
Compressor - lz4hc
zmalloc zpool - z3fold
Memory pool - 18.00 %
STATS
-----
Pool total size - 3.20 MiB
Original data size - 8.46 MiB
Estimated savings - 5.27 MiB
Written back pages - 10803
Stored (cached) pages - 2167
Uncompressible pages - 5
Compression ratio - 2.65
Gathering stats info for zram device "zram0"
ZRAM
----
Block device - /sys/block/zram0
Device size - 185 MiB
Compression algo - lzo lz4 lz4hc [zstd]
Compression streams - 4
DATA
----
Original data size - 44.04 MiB
Compressed data size - 10.59 MiB
Estimated savings - 33.45 MiB
Compression ratio - 4.16
Expected c. ratio - 4.25
MEMORY
------
Memory used, total - 11.56 MiB
Allocator overhead - 0.98 MiB
Allocator efficiency - 91.55 %
Maximum memory ever used - 11.77 MiB
Memory limit - 43.53 MiB
PAGES
-----
Same pages count - 0
Pages compacted - 0
Free pages discarded - 148670
Swap usage after the forced load
root@EA6350v3:~# stress --vm 4 --vm-bytes 250M --timeout 10s
stress: info: [21889] dispatching hogs: 0 cpu, 0 io, 4 vm, 0 hdd
stress: info: [21889] successful run completed in 11s
root@EA6350v3:~# swapon -s
Filename Type Size Used Priority
/dev/sdb1 partition 4194300 0 -2
/dev/zram0 partition 189436 49308 1
For the future release (nov 15, 2019) you can check all of that information by running zram status
in your terminal/shell (however you call it).