[閒聊] 虛擬記憶體的問題
最近跟同事討論到virtual memory的部分,
發現觀念不太一樣,對virtual memory有兩種不同的說法,
第一種說法:
virtual memory就是硬碟,當main memory不夠時,
OS會將main memory中的一些page移到硬碟中,
當程式用到這些page時,會再將這些page從硬碟中移到main memory裡。
簡單說就是,硬碟的一部分會當作memory使用,但因為硬碟不是真正的memory
故稱作virtual memory。
第二種說法:
virtual memory和physical memory是相對的,
physical memory就是你實體機器所擁有的memory,
比方說你的平台插了一條2G的memory,那physical memory就是2G。
而virtual memory為process所認知的memory,
每個process都認為自己擁有4G的空間(依OS規定),而且address從0開始。
而OS會負責將process認知的virtual memory對應到真實的physical memory。
請問哪個說法才是對的呢?
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