鎿嶄綔绯荤粺绗簩娆′綔涓?/p>
绗簲绔?/p>
5.1 Why is it important for the scheduler to distinguish I/O-bound programs from
CPU-bound programs?
涓轰綍璋冨害鍣ㄨ鍖哄垎
IO
绾︽潫绋嬪簭鍜?/p>
CPU
绾︽潫绋嬪簭锛?/p>
绛旓細浜岃�呭
CPU
鐨勪娇鐢ㄦ湁杈冨ぇ宸埆锛?/p>
IO
鎿嶄綔鍙渶灏戦噺鐨?/p>
CPU
鏃堕棿鐗囷紝澶ч儴鍒嗘椂
闂寸敤浜?/p>
IO
鐨勭瓑寰咃紝鑰?/p>
CPU
绾︽潫鎿嶄綔闇�瑕佺敤鏁村潡鏃堕棿锛屽湪
CPU
鎿嶄綔鐨勫悗鍙板彲浠ュ悓
鏃惰繍琛?/p>
IO
绛夊緟鎿嶄綔锛屼簩鑰呬簰涓嶅奖鍝嶏紝閫氳繃鍖哄垎涓ょ鎿嶄綔锛屽姞涓婄郴缁熺殑璋冨害锛屽彲
浠ユ洿濂界殑鍒╃敤
CPU
璧勬簮锛屾彁楂樿繍琛屾晥鐜?/p>
5.3 Consider the exponential average formula used to predict the length of the next
CPU
burst.
What
are
the
implications
of
assigning
the
following
values
to
the
parameters used by the algorithm?
a. = 0 and 0 = 100milliseconds
b. = 0.99 and 0 = 10milliseconds
鑰冭檻棰勬祴涓嬩竴涓?/p>
CPU
鍖洪棿鐨勬寚鏁板钩鍧囧叕寮忥紝褰撲笅鍒楀弬鏁板垎鍒彇瀵瑰簲鍊兼椂鐨勫奖鍝?/p>
鏄粈涔?/p>
绛旓細鎸囨暟骞冲潎鍏紡锛?/p>
T(n+1)=at(n)+(1-a)Tn
鍙傛暟
Tn+1
鐨勫惈涔夋槸棰勬祴涓嬩竴
CPU
鍖洪棿鐨勯娴嬪�硷紝
tn
涓虹
n
涓?/p>
CPU
鍖洪棿鐨勯暱
搴︼紝
a
浠ｈ〃棰勬祴鍊煎拰涓婁竴鍖洪棿闀垮害鐨勩�愮浉鍏冲害銆?/p>
锛屼篃灏辨槸璇达紝
a
鍙栧�艰秺澶э紝涓婁竴涓?/p>
鍖洪棿锛堢湡瀹炲彂鐢熺殑锛夐暱搴﹀棰勬祴鍊肩殑褰卞搷灏辫秺澶э紝鍙嶄箣锛?/p>
a
鍙栧�艰秺灏忥紝棰勬祴鍊煎氨
涓昏浣撶幇涓轰笂涓�娆＄殑棰勬祴鍊笺�?/p>
a=0
锛?/p>
t=100ms
a=0
浠ｈ〃鐪熷疄鍙戠敓鐨勫尯闂撮暱搴︿笉浼氬奖鍝嶉娴嬶紝涔熷氨鏄棰勬祴鍊间細涓�鐩翠繚鎸佷负
涓婁竴娆￠娴嬪�硷紝鍗?/p>
t
锛屾晠鏈棰勬祴鍊间负
100ms
a=0.99 t=10ms
a=0.99
浠ｈ〃棰勬祴鍊煎熀鏈畬鍏ㄤ綋鐜颁负涓婁竴娆＄湡瀹炲彂鐢熺殑
CPU
鍖洪棿闀垮害锛?/p>
涔熷氨鏄?/p>
璇撮娴嬪�煎熀鏈槸鍓嶄竴涓尯闂寸殑闀垮害锛屾瘮濡?/p>
tn=50ms
锛屽垯涓嬩竴娆￠娴嬪�间篃澶ц嚧涓?/p>
50ms
銆?/p>
5.4 Consider the following set of processes, with the length of the CPU-burst time
given in milliseconds:
Process Burst Time Priority
P1
10
3
P2
1
1
P3
2
3
P4
1
4
P5
5
2
The processes are assumed to have arrived in the order P1 , P2 ,P3 , P4 , P5 , all at
time 0.
a. Draw four Gantt charts illustrating the execution of these processes using FCFS,
SJF, a nonpreemptive priority (a smaller priority number implies a higher priority),