Guide: Async IO

Enter the labs/lab-11/guides/async/ folder for some implementations of a simple request-reply server in C. Here we have the implementation of a server that computes the n-th fibonacci number. The server serves requests in different ways:

synchronous server: server.c
multiprocess server: mp_server.c
multithreaded server: mt_server.c

Note: There is no asynchronous C variant, because of the unstable API of libaio and io_uring.

Benchmark the synchronous server to have a reference point. Run ./server 2999 in one terminal and time ./client_bench.sh 2999 in another. client_bench.sh we’ll run 8 instances of client.py that make a request.
```
student@os:~/async/support$ time ./client_bench.sh 2000
[...]
root: Connected to localhost:2000
root: Sending 30
function(30): 1346269

real    0m1.075s
user    0m0.301s
sys     0m0.029s
```
The value you obtain might be different, but you should observe a speed-up when benchmarking the other two solutions.
Benchmark the multiprocess and multithreaded alternatives and see which one got the best speed increase. You can obtain more relevant values by tweaking parameters in client_bench.sh. For example, you could increase the number of clients or the fibonacci value to compute.
Begin by benchmarking the synchronous server to establish a baseline. Run ./server 2999 in one terminal and time ./client_bench.sh 2999 in another. The client_bench.sh script will initiate 8 instances of client.py, each making a request. The output might look like this:
```
student@os:~/async/support$ time ./client_bench.sh 2000
[...]
root: Connected to localhost:2000
root: Sending 30
function(30): 1346269

real    0m1.075s
user    0m0.301s
sys     0m0.029s
```
Although the actual value may vary, you should observe a noticeable speed-up when testing the other two solutions.
Next, benchmark the multiprocess and multithreaded alternatives to determine which offers the best performance improvement. To obtain more meaningful results, adjust parameters in client_bench.sh, such as increasing the number of clients or the Fibonacci value to compute.

If you’re having difficulties understanding the support code, go through this reading material. If you want to practice this yourself, go through the Async Server task.