--- tags: linux2024 --- # [2024q1](https://wiki.csie.ncku.edu.tw/linux/schedule) 第 15 週測驗題 :::info 目的: 檢驗學員對[並行和多執行緒程式設計](https://hackmd.io/@sysprog/concurrency)的認知 ::: ==[作答表單](https://docs.google.com/forms/d/e/1FAIpQLSeD8AXS-ig9Z_oC82U94-fm16GmoqOx2Gmlk0vST5VbHbp7MA/viewform)== ### 測驗 `1` 考慮我們嘗試建構 lock-free 的 MPMC broadcast queue、依循 [Publish–subscribe](https://en.wikipedia.org/wiki/Publish%E2%80%93subscribe_pattern) 模式，程式碼可見 [broadcast](https://gist.github.com/jserv/097c58737b3b87c1e72c8938d2b3b5a2)，其中 `pool.[ch]` 是 lock-free memory pool。 編譯方式: ```shell $ gcc -Wall -O2 -D_GNU_SOURCE \ -o stress \ stress.c \ broadcast.c \ pool.c \ -lpthread ``` 參考執行輸出: ``` Test: 1pub0sub Pub Thread 0 | n_msgs: 100000 n_drops: 0 | 169 ns/msg Test: 2pub0sub Pub Thread 0 | n_msgs: 100000 n_drops: 0 | 519 ns/msg Pub Thread 1 | n_msgs: 100000 n_drops: 0 | 416 ns/msg Test: 4pub0sub Pub Thread 0 | n_msgs: 100000 n_drops: 0 | 945 ns/msg Pub Thread 1 | n_msgs: 100000 n_drops: 0 | 965 ns/msg Pub Thread 2 | n_msgs: 100000 n_drops: 0 | 952 ns/msg Pub Thread 3 | n_msgs: 100000 n_drops: 0 | 967 ns/msg Test: 4pub0sub Pub Thread 0 | n_msgs: 100000 n_drops: 0 | 2800 ns/msg Pub Thread 1 | n_msgs: 100000 n_drops: 0 | 3015 ns/msg Pub Thread 2 | n_msgs: 100000 n_drops: 0 | 3065 ns/msg Pub Thread 3 | n_msgs: 100000 n_drops: 0 | 3060 ns/msg Pub Thread 4 | n_msgs: 100000 n_drops: 0 | 3062 ns/msg Pub Thread 5 | n_msgs: 100000 n_drops: 0 | 3033 ns/msg Pub Thread 6 | n_msgs: 100000 n_drops: 0 | 3021 ns/msg Pub Thread 7 | n_msgs: 100000 n_drops: 0 | 3043 ns/msg ``` AAAA, BBBB, CCCC, DDDD, EEEE, FFFF 皆為變數名稱