Weird CPU utilization patterns with Postgres

Few days ago our box started to show huge CPU spikes while the IO Wait is negligible on the box. After a while I have installed perf and started to monitor the Postgres master process and here is what I have found:

Samples: 372K of event 'cycles', Event count (approx.): 110095222173, ThreaSamples: 372K of event 'cycles', Event count (approx.): 1100 93.65%  libc-2.12.so  [.] __strcoll_l
  0.97%  libc-2.12.so  [.] memcpy
  0.90%  postgres      [.] slot_getattr
  0.88%  postgres      [.] nocachegetattr
  0.64%  postgres      [.] varstr_cmp
  0.52%  libc-2.12.so  [.] __strcmp_sse42
  0.43%  postgres      [.] hash_any
  0.32%  postgres      [.] pg_detoast_datum_packed
  0.31%  libc-2.12.so  [.] __strlen_sse2
  0.22%  postgres      [.] bttextcmp
  0.18%  postgres      [.] ExecStoreTuple
  0.14%  postgres      [.] MemoryContextReset
  0.09%  postgres      [.] pgstat_end_function_usage
  0.08%  libc-2.12.so  [.] strcoll
  0.08%  postgres      [.] heap_hot_search_buffer
  0.07%  postgres      [.] lc_collate_is_c
  0.06%  [kernel]      [k] sys_semtimedop
  0.06%  postgres      [.] heap_page_prune_opt
  0.05%  postgres      [.] slot_getsomeattrs
  0.05%  postgres      [.] heap_fill_tuple
  0.04%  postgres      [.] hash_search
  0.03%  postgres      [.] GetMemoryChunkSpace
  0.03%  postgres      [.] heap_form_minimal_tuple
  0.03%  [kernel]      [k] update_queue
  0.02%  postgres      [.] ReadBufferExtended
  0.02%  postgres      [.] memcpy@plt