Same problem here:
- No swap machine
- Wily (U15.10) - 4.2.0-19-generic #23-Ubuntu SMP Wed Nov 11 11:39:30 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
- 1GB RAM

- `meminfo` - Should have enough RAM to not swap though buffers do seem high

MemTotal:        1014932 kB
MemFree:          231296 kB
MemAvailable:     871180 kB
Buffers:          580684 kB
Cached:            47812 kB
SwapCached:            0 kB
Active:           547952 kB
Inactive:         164364 kB
Active(anon):      84280 kB
Inactive(anon):     4288 kB
Active(file):     463672 kB
Inactive(file):   160076 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Dirty:               224 kB
Writeback:             0 kB
AnonPages:         83800 kB
Mapped:            39688 kB
Shmem:              4768 kB
Slab:              48008 kB
SReclaimable:      31172 kB
SUnreclaim:        16836 kB
KernelStack:        1936 kB
PageTables:         3844 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:      507464 kB
Committed_AS:     314640 kB
VmallocTotal:   34359738367 kB
VmallocUsed:       13524 kB
VmallocChunk:   34359717628 kB
HardwareCorrupted:     0 kB
AnonHugePages:     49152 kB
CmaTotal:              0 kB
CmaFree:               0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:       53248 kB
DirectMap2M:     1126400 kB

- kernel config: https://gist.github.com/sgnn7/cbb41ce21d3a927eca27

- strace shows nothing interesting

- `perf` report:
Samples: 12K of event 'cpu-clock', Event count (approx.): 3245250000                                                                                                                                                                               
Overhead  Command  Shared Object      Symbol                                                                                                                                                                                                       
  19.34%  kswapd0  [kernel.kallsyms]  [k] shrink_lruvec                                                                                                                                                                                            
  17.04%  kswapd0  [kernel.kallsyms]  [k] mem_cgroup_iter                                                                                                                                                                                          
   8.60%  kswapd0  [kernel.kallsyms]  [k] mem_cgroup_zone_lruvec                                                                                                                                                                                   
   6.57%  kswapd0  [kernel.kallsyms]  [k] shrink_slab                                                                                                                                                                                              
   5.47%  kswapd0  [kernel.kallsyms]  [k] global_dirty_limits                                                                                                                                                                                      
   4.18%  kswapd0  [kernel.kallsyms]  [k] domain_dirty_limits                                                                                                                                                                                      
   3.71%  kswapd0  [kernel.kallsyms]  [k] mem_cgroup_get_lru_size                                                                                                                                                                                  
   3.59%  kswapd0  [kernel.kallsyms]  [k] super_cache_count                                                                                                                                                                                        
   3.27%  kswapd0  [kernel.kallsyms]  [k] get_lru_size                                                                                                                                                                                             
   3.26%  kswapd0  [kernel.kallsyms]  [k] throttle_vm_writeout                                                                                                                                                                                     
   2.20%  kswapd0  [kernel.kallsyms]  [k] css_next_descendant_pre                                                                                                                                                                                  
   2.15%  kswapd0  [kernel.kallsyms]  [k] blk_flush_plug_list                                                                                                                                                                                      
   1.96%  kswapd0  [kernel.kallsyms]  [k] shrink_zone                                                                                                                                                                                              
   1.73%  kswapd0  [kernel.kallsyms]  [k] _raw_spin_lock                                                                                                                                                                                           
   1.59%  kswapd0  [kernel.kallsyms]  [k] __list_lru_count_one.isra.2                                                                                                                                                                              
   1.43%  kswapd0  [kernel.kallsyms]  [k] list_lru_count_one                                                                                                                                                                                       
   1.37%  kswapd0  [kernel.kallsyms]  [k] memcg_kmem_is_active                                                                                                                                                                                     
   1.27%  kswapd0  [kernel.kallsyms]  [k] __raw_callee_save___pv_queued_spin_unlock                                                                                                                                                                
...


I'm going to try gdb, changing swappiness, changing vm.min_free_kbytes, and reducing buffer limits in that order and report back but most likely I'll have one shot before the bug goes away for the next few days.