Update redis-questions-01.md

对Redis6.0 多线程的描述有点问题
io-threads-do-reads 并不是开启IO多线程，而是开启IO多线程读

################################ THREADED I/O #################################

# Redis is mostly single threaded, however there are certain threaded
# operations such as UNLINK, slow I/O accesses and other things that are
# performed on side threads.
#
# Now it is also possible to handle Redis clients socket reads and writes
# in different I/O threads. Since especially writing is so slow, normally
# Redis users use pipelining in order to speed up the Redis performances per
# core, and spawn multiple instances in order to scale more. Using I/O
# threads it is possible to easily speedup two times Redis without resorting
# to pipelining nor sharding of the instance.
#
# By default threading is disabled, we suggest enabling it only in machines
# that have at least 4 or more cores, leaving at least one spare core.
# Using more than 8 threads is unlikely to help much. We also recommend using
# threaded I/O only if you actually have performance problems, with Redis
# instances being able to use a quite big percentage of CPU time, otherwise
# there is no point in using this feature.
#
# So for instance if you have a four cores boxes, try to use 2 or 3 I/O
# threads, if you have a 8 cores, try to use 6 threads. In order to
# enable I/O threads use the following configuration directive:
#
# io-threads 4
#
# Setting io-threads to 1 will just use the main thread as usual.
# When I/O threads are enabled, we only use threads for writes, that is
# to thread the write(2) syscall and transfer the client buffers to the
# socket. However it is also possible to enable threading of reads and
# protocol parsing using the following configuration directive, by setting
# it to yes:
#
# io-threads-do-reads no
#
# Usually threading reads doesn't help much.
#
# NOTE 1: This configuration directive cannot be changed at runtime via
# CONFIG SET. Aso this feature currently does not work when SSL is
# enabled.
#
# NOTE 2: If you want to test the Redis speedup using redis-benchmark, make
# sure you also run the benchmark itself in threaded mode, using the
# --threads option to match the number of Redis threads, otherwise you'll not
# be able to notice the improvements.

Author: NoctisZhao

docs/database/redis/redis-questions-01.md

@@ -364,17 +364,21 @@ Redis 通过 **IO 多路复用程序** 来监听来自客户端的大量连接
 
 虽然，Redis6.0 引入了多线程，但是 Redis 的多线程只是在网络数据的读写这类耗时操作上使用了，执行命令仍然是单线程顺序执行。因此，你也不需要担心线程安全问题。
 
-Redis6.0 的多线程默认是禁用的，只使用主线程。如需开启需要修改 redis 配置文件 `redis.conf` ：
+Redis6.0 的多线程默认是禁用的，只使用主线程。如需开启需要设置IO线程数 > 1，需要修改 redis 配置文件 `redis.conf` ：
 
 ```bash
-io-threads-do-reads yes
+io-threads 4 #设置1的话只会开启主线程，官网建议4核的机器建议设置为2或3个线程，8核的建议设置为6个线程
 ```
+另外：
+- io-threads的个数一旦设置，不能通过config动态设置
+- 当设置ssl后，io-threads将不工作
 
-开启多线程后，还需要设置线程数，否则是不生效的。同样需要修改 redis 配置文件 `redis.conf` :
+开启多线程后，默认只会使用多线程进行IO写入writes，即发送数据给客户端，如果需要开启多线程IO读取reads，同样需要修改 redis 配置文件 `redis.conf` :
 
 ```bash
-io-threads 4 #官网建议4核的机器建议设置为2或3个线程，8核的建议设置为6个线程
+io-threads-do-reads yes
 ```
+但是官网描述开启多线程读并不能有太大提升，因此一般情况下并不建议开启
 
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