How can I find out what is making my SLAB Unreclaimable Memory Grow without bound

My SLAB unreclaimable memory (SUnreclaim) grows without bounds and this appears to be the reason why my system eventually runs out of RAM and starts trying to swap until it dies. Here's a graph of my SUreclaim over a couple of days. My typical RAM usage is about 5GB on a 16GB server. When the SUreclaim gets to about 10.xGB the endless swapping starts. These graphs show it growing endlessly and me rebooting it to free up the RAM, in these 2 cases, before it causes my system to swap itself to death. Here's a partial slabtop just before the 2nd reboot. ---------------------------------- 20180730164416 ---------------------------------- Active / Total Objects (% used) : 34014938 / 35150125 (96.8%) Active / Total Slabs (% used) : 1098114 / 1098114 (100.0%) Active / Total Caches (% used) : 120 / 147 (81.6%) Active / Total Size (% used) : 7332279.93K / 7831039.90K (93.6%) Minimum / Average / Maximum Object : 0.01K / 0.22K / 22.88K OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME 8433792 8349318 98% 0.06K 131778 64 527112K pid 4253942 4250995 99% 0.09K 92477 46 369908K anon_vma 3011640 2929311 97% 0.20K 150582 20 602328K vm_area_struct 2994831 2908345 97% 0.19K 142611 21 570444K dentry 2068096 2033715 98% 0.03K 16157 128 64628K kmalloc-32 1953024 1932838 98% 0.02K 7629 256 30516K kmalloc-16 1820128 1618465 88% 0.25K 113758 16 455032K filp 1149438 1149438 100% 0.04K 11269 102 45076K pde_opener 1014336 891822 87% 0.06K 15849 64 63396K kmalloc-64 954051 953969 99% 0.19K 45431 21 181724K cred_jar 757224 752612 99% 0.10K 19416 39 77664K buffer_head 627368 627368 100% 0.07K 11203 56 44812K eventpoll_pwq 564900 535453 94% 0.09K 13450 42 53800K kmalloc-96 372690 336229 90% 0.13K 12423 30 49692K kernfs_node_cache 362528 362365 99% 0.12K 11329 32 45316K seq_file 329937 327195 99% 1.06K 21455 30 686560K signal_cache task_struct is also normally very high and is normally about 1.5GB before I have to reboot. A couple of questions: 1) How do I work out which SLAB caches contain the unreclaimable RAM? 2) Is there anything else I can do to work out why the RAM is unreclaimable?