this nodes role is slave, version is 4.0.12, the machine swap is off,

Memory

used_memory:6055275128 used_memory_human:5.64G used_memory_rss:5298495488 used_memory_rss_human:4.93G used_memory_peak:6164388792 used_memory_peak_human:5.74G used_memory_peak_perc:98.23% used_memory_overhead:148465818 used_memory_startup:1954224 used_memory_dataset:5906809310 used_memory_dataset_perc:97.58% ...... used_memory_lua:37888 used_memory_lua_human:37.00K maxmemory:7516192768 maxmemory_human:7.00G maxmemory_policy:noeviction mem_fragmentation_ratio:0.88 mem_allocator:jemalloc-4.0.3

machine: CentOS release 6.9 (Final)

Comment From: judeng

perhaps your many data point to the zero page, Please refer to https://github.com/redis/redis/issues/946#issuecomment-13599772