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    ###### tags: `Linux`, `SRE` # SRE 讀書會 Round 4 #03 - 線上讀書會共筆 ## 活動資訊 * Date: 2020/05/21 (四) 20:00 - 21:30 * [導讀進度表](https://docs.google.com/spreadsheets/d/1Lgti3mILkvwxyzklX1vvLraaGD-7ePK9rkmlulfOknE/edit#gid=0) * [導讀 Guideline](https://study-area.sre.tw/GuideLine/) * Github: [study-area-docs](https://github.com/cross-community/study-area-docs) --- ## 現場共筆 ### 軟中斷 ### 硬中斷 現在有些設計反其道而行,就是一直再那邊看外送員有沒有來,用 CPU換效能 Intel 有些 CPU數量很多 所以會使用這種方式 Polling > [Data Plane Development Kit, DPDK](https://zh.wikipedia.org/zh-tw/DPDK) 1. top half => 快速執行 Critical effect ,在執行的時候不能進入睡眠,可以lock (spin lock) 2. button half => 延遲執行 可以晚點再做, 可以匯入 queue 中的 3. hardware interrupt =>由硬體做源頭 4. software interrupt =>由軟體(user)做源頭 (指標找不到, 1/0 等 ) ## 問題討論 Q: 為什麼要有殭屍程序? > * 殭屍程序對應用程式來說,可能是有意義的 > * [why zombie process necessary](https://stackoverflow.com/questions/16416793/why-is-a-zombie-process-necessary) Q: 殭屍程序有可能復活? > 不知道是誰在管理的 所以沒辦法復活 Q: 為什麼 OS 不自動把殭屍程序處理掉? 經驗分享: 有服務需要每個小時重開一次 Q: 一台長期不容易安排重開機的 application client node, 記憶體仍剩下數百G, swappiness 設置=1, 但有部分系統程序例如 systemd, rsyslogd, …等.. 吃到SWAP, 例如加總一半的空間, 執行 swapoff , swapon 存在崩潰的風險, 除了不理他並安排重新啟動, 有沒有更好的方法? Q: 作者好像對於軟中斷類型的介紹很簡單帶過,上網查說軟中斷又有tasklet, workqueue等等類型,看到有點混淆,不知道有沒有對這方面熟悉的大大可以幫忙解惑一下這部分? > 中斷打進來,上半部:快速執行(不允許睡眠,可以busy lock/spin lock)、下半部:延遲執行 > workqueue 針對IO --- # 參考資料 * [why zombie process necessary](https://stackoverflow.com/questions/16416793/why-is-a-zombie-process-necessary)

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