春节前几天运维大侠说要扩容 Redis 从库但同步一直失败，看日志发现在做 bgsave 的时候一直失败。 日志如下:
[41738] 04 Feb 11:16:39.859 * Full resync requested by slave.
[41738] 04 Feb 11:16:39.859 * Starting BGSAVE for SYNC
[41738] 04 Feb 11:16:39.860 # Can't save in background: fork: Cannot allocate memory
[41738] 04 Feb 11:16:39.860 * Replication failed, can't BGSAVE
从日志可以看到 fork 的时候内存分配失败导致 bgsave 无法成功，那就是可用内存不足?