I have 8 GB RAM and a 8 GB swap partition and I set vm.swappiness to 90 in /etc/sysctl.conf (and verified that it's used with the sysctl command at runtime). The system uses 50 % of RAM and 40 % of swap and this situation is approximately the same after running sudo swapoff -a && sudo swapon -a and a delay of minutes. Also I see that swapping of ca. 100 MB occurs regularily at runtime.
I don't understand why the memory isn't filled up to 90 % as suggested by vm.swappiness.
I experienced with issue with Linux 4.4.0-22 and 4.5.7 on Ubuntu 16.04.
$ cat /proc/meminfo
MemTotal: 8030020 kB
MemFree: 220724 kB
MemAvailable: 4418060 kB
Buffers: 86456 kB
Cached: 4090160 kB
SwapCached: 184660 kB
Active: 3779408 kB
Inactive: 2730596 kB
Active(anon): 1736480 kB
Inactive(anon): 955376 kB
Active(file): 2042928 kB
Inactive(file): 1775220 kB
Unevictable: 62848 kB
Mlocked: 62848 kB
SwapTotal: 8462332 kB
SwapFree: 5576576 kB
Dirty: 40332 kB
Writeback: 0 kB
AnonPages: 2312568 kB
Mapped: 315084 kB
Shmem: 351016 kB
Slab: 1039608 kB
SReclaimable: 937796 kB
SUnreclaim: 101812 kB
KernelStack: 15744 kB
PageTables: 53896 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 12477340 kB
Committed_AS: 10436316 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 0 kB
VmallocChunk: 0 kB
HardwareCorrupted: 0 kB
AnonHugePages: 448512 kB
CmaTotal: 0 kB
CmaFree: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 369540 kB
DirectMap2M: 7874560 kB
