How can Redis be optimized from this INFO?

Question

Redis

Good afternoon, I recently started working with Redis but faced a slowdown after 2 million.
At the moment there are 2 hash tables with 2.5 million records each. But there is a significant slowdown in the search for keys, apparently. Here is the INFO log, if you have any advice, please write.)

Server #
redis_version: 2.8.17
redis_git_sha1: 00000000
redis_git_dirty: 0
redis_build_id: 5b70b85861dcf95e
redis_mode: the standalone
os: the Linux 3.16.0-6 amd64-the x86_64
arch_bits: 64
multiplexing_api: the epoll
gcc_version: 4.9.2
process_id: 490
run_id: 601e2aee6f480248a4b5b945011e024eb8ed9e3b
TCP_PORT: 6379
uptime_in_seconds:8743
uptime_in_days:0
hz:10
lru_clock:328166
config_file:/etc/redis/redis.conf
# Clients
connected_clients:5
client_longest_output_list:0
client_biggest_input_buf:0
blocked_clients:0
# Memory
used_memory:807227136
used_memory_human: 769.83M
used_memory_rss: 817348608
used_memory_peak: 807264168
used_memory_peak_human: 769.87M
used_memory_lua: 33792
mem_fragmentation_ratio: 1.01
mem_allocator: jemalloc-3.6.0
# Persistence
loading: 0
rdb_changes_since_last_save: 56553
rdb_bgsave_in_progress: 0
rdb_last_save_time: 1543832012
rdb_last_bgsave_status: ok
The rdb_last_bgsave_time_sec: 6
rdb_current_bgsave_time_sec: - 1
aof_enabled:0
aof_rewrite_in_progress:0
aof_rewrite_scheduled:0
aof_last_rewrite_time_sec:-1
aof_current_rewrite_time_sec:-1
aof_last_bgrewrite_status:ok
aof_last_write_status:ok
# Stats
total_connections_received: 17
total_commands_processed: 36775621
instantaneous_ops_per_sec: 0
rejected_connections: 0
sync_full: 0
sync_partial_ok: 0
sync_partial_err: 0
expired_keys: 0
evicted_keys: 0
keyspace_hits: 28859122
keyspace_misses: 31111
pubsub_channels: 0
pubsub_patterns: 0
latest_fork_usec: 10474
# the Replication
role: the master
connected_slaves :0
master_repl_offset:0
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0
# CPU
used_cpu_sys:533.66
used_cpu_user:181.83
used_cpu_sys_children:
34.63 used_cpu_user_children:177.54
# Keyspace
db0:keys=4,expires=0,avg_ttl=0
db7:keys=17,expires=0,avg_ttl=0