modify doc

About.md

@@ -35,15 +35,39 @@ Supports HTTP/1.1, can be used in client and server sides.
 - ...
 
 # 2.2. Redis client
-- Supports Bitmap/String/Hash/List/Set/Sorted Set/PubSub/HyperLogLog/Geo/Script/Stream/Server/Cluster/etc.
+The redis client module in Acl is powerful, high-performance and easy to use.
+- Support Bitmap/String/Hash/List/Set/Sorted Set/PubSub/HyperLogLog/Geo/Script/Stream/Server/Cluster/etc.
 - Provides stl-like C++ interface for each redis command
 - Communication in single, cluster or pipeline mode
 - Connection pool be used in signle or cluster mode
-- More information see [Using redis](lib_acl_cpp/samples/redis/README.md)
+- More information see [Using acl redis client](lib_acl_cpp/samples/redis/README.md)
 
 # 2.3. Coroutine
+The coroutine module in Acl can be used on multiple platforms, and there are many engineering practices in some important projects.
+- Run on Linux, MacOS, Windows, iOS and Android
+- Support x86, Arm architecture
+- Support select/poll/epoll/kqueue/iocp/win32 GUI message
+- The DNS protocol has been implemented in acl coroutine, so DNS API can also be used in coroutine model
+- Hook system IO API on Unix and Windows
+  - Read API: read/readv/recv/recvfrom/recvmsg
+  - Write API: write/writev/send/sendto/sendmsg/sendfile64
+  - Socket API: socket/listen/accept/connect/setsockopt
+  - event API: select/poll/epoll_create/epoll_ctl/epoll_wait
+  - DNS API: gethostbyname/gethostbyname_r/getaddrinfo/freeaddrinfo
+- Support shared stack mode to minimize memory usage
+- Synchronization primitive
+  - Coroutine mutex, semphore can be used between coroutines
+  - Coroutine event can be used between coroutines and threads
+- More information see [Using acl fiber](lib_fiber/README_en.md)
 
 # 2.4. Server framework
+The most important module in Acl is the server framework, which helps users quickly write back-end services, such as web services. Tools in app/wizard can help users generate one appropriate service code within several seconds. The server framework of Acl includes two parts, one is the services manager, the other is the service written by Acl service template. The services manager named acl_master in Acl comes from the famous Postfix, whose name is master, and acl_master has many extensions to master in order to be as one general services manager. There are six service templates in Acl that can be used to write application services, as below:
+- **Process service:** One connection one process, the advantage is that the programming is simple, safe and stable, and the disadvantage is that the concurrency is too low;
+- **Threads service:** Each process handles all client connections through a set of threads in the thread pool. The IO event trigger mode is used that a connection is bound to a thread only if it has readable data, and the thread will be released after processing the data. The service model's advantage is that it can handle a large number of client connections in one process with a small number of threads. Compare with the aio model, the programming is relatively simple;
+- **Aio service:** Similar to nginx/squid/ircd, one thread can handle a large number of client connections in a non-blocking IO manner. The advantages of this model are high processing efficiency and low resource consumption, while the disadvantages are more complex programming;
+- **Fiber service:** Although the non-blocking service model can obtain large concurrent processing capability, the programming complexity is high. The coroutine model combines the features of large concurrent processing and low programming complexity, enabling programmers to easily implement sequential IO programming;
+- **UDP service:** The model is mainly a service model supporting UDP communication process;
+- **Trigger service:** The model instance is mainly used to process the background service process of some scheduled tasks (similar to the system's crontab).
 
 # 2.5. Database module