redis 报错 Can‘t save in background fork Cannot allocate memory

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我是靠谱客的博主俊秀铅笔，最近开发中收集的这篇文章主要介绍redis 报错 Can‘t save in background fork Cannot allocate memory，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

redis-cli -p 12345

[root@localhost ~]# redis-cli -p 6379
127.0.0.1:6379> auth "123456"
OK
127.0.0.1:6379> info
# Server
redis_version:3.2.12
redis_git_sha1:00000000
redis_git_dirty:0
redis_build_id:7897e7d0e13773f
redis_mode:standalone
os:Linux 3.10.0-1127.19.1.el7.x86_64 x86_64
arch_bits:64
multiplexing_api:epoll
gcc_version:4.8.5
process_id:1242
run_id:XXX
tcp_port:6379
uptime_in_seconds:1186639
uptime_in_days:13
hz:10
lru_clock:11977524
executable:/usr/bin/redis-server
config_file:/etc/redis.conf

# Clients
connected_clients:1
client_longest_output_list:0
client_biggest_input_buf:0
blocked_clients:0

# Memory
used_memory:3486652368
used_memory_human:3.25G
used_memory_rss:3548164096
used_memory_rss_human:3.30G
used_memory_peak:3486886808
used_memory_peak_human:3.25G
total_system_memory:16637546496
total_system_memory_human:15.49G
used_memory_lua:37888
used_memory_lua_human:37.00K
maxmemory:0
maxmemory_human:0B
maxmemory_policy:noeviction
mem_fragmentation_ratio:1.02
mem_allocator:jemalloc-3.6.0

# Persistence
loading:0
rdb_changes_since_last_save:8
rdb_bgsave_in_progress:0
rdb_last_save_time:1639367433
rdb_last_bgsave_status:ok
rdb_last_bgsave_time_sec:20
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:3831251
total_commands_processed:18072447
instantaneous_ops_per_sec:15
total_net_input_bytes:1538227697
total_net_output_bytes:907587826299
instantaneous_input_kbps:0.61
instantaneous_output_kbps:3.07
rejected_connections:0
sync_full:0
sync_partial_ok:0
sync_partial_err:0
expired_keys:0
evicted_keys:0
keyspace_hits:7332354
keyspace_misses:6533
pubsub_channels:0
pubsub_patterns:0
latest_fork_usec:2025
migrate_cached_sockets:0

# Replication
role: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:1586.86
used_cpu_user:625.00
used_cpu_sys_children:3198.40
used_cpu_user_children:46091.06

# Cluster
cluster_enabled:0

# Keyspace
db0:keys=936,expires=0,avg_ttl=0

redis maxmemory:0 内存这个是没有做任何限制的

linux

[root@localhost redis]# sysctl -a|grep overcommit_memory

vm.overcommit_memory = 0

vm.overcommit_memory = 0 启发策略此次请求分配的虚拟内存大小和系统当前空闲的物理内存加上swap，决定是否放行。系统在为应用进程分配虚拟地址空间时，会判断当前申请的虚拟地址空间大小是否超过剩余内存大小，如果超过，则虚拟地址空间分配失败。

redis在保存内存的数据到磁盘时，为了防止主进程假死，会Fork一个子进程来完成这个保存操作。但是这个Fork的子进程会需要分配和主进程相同的内存，这时候就相当于需要的内存double了，如果这时候可用内存不足以分配需要的内存，将会导致Fork子进程失败而无法保存数据到磁盘。

/etc/redis.conf

[root@localhost etc]# more redis.conf |grep "stop-writes-on-bgsave-error"

stop-writes-on-bgsave-error yes