used_memory greater than used_memory_rss?

[Gen Liu]

Hello everybody,  Redis's used_memory is greater than used_memory_rss. Is this supposed to happen ?  

If so, can you help me understand how this works, Thank you!

redis info shows the following

# Server

redis_version:3.0.0

redis_git_sha1:00000000

redis_git_dirty:0

redis_build_id:b0ad6d614e1accd

redis_mode:standalone

arch_bits:64

multiplexing_api:epoll

gcc_version:4.4.7

process_id:9

run_id:2e18e3528a221d0253b451274153b2bf50a3d828

tcp_port:6379

uptime_in_seconds:32831793

uptime_in_days:379

hz:10

lru_clock:5646543

# Memory

used_memory:1083860248

used_memory_human:1.01G

used_memory_rss:910970880

used_memory_peak:1147718680

used_memory_peak_human:1.07G

used_memory_lua:35840

mem_fragmentation_ratio:0.84

mem_allocator:jemalloc-3.6.0