M.I.T. DEPARTMENT OF EECS
|6.033 - Computer System Engineering||Handout 16 - March 11, 2002|
Distribution of Scores
The intention was that answer B be true, because when several AMPED helper processes issue disk reads at about the same time, the disk driver can discover them and schedule those reads in batches to improve performance. Since SPED must wait for one disk read to complete before it can issue another one, it misses this opportunity. But the definition of batching given in the glossary of chapter 3 accidentally got out of sync with this question; that definition requires delaying an operation until a time when it can be combined with another operation. Any disk driver that takes that strategy would probably speed up AMPED and SPED equally well, which would make B false.
... A, E, F, B, ...
The web server is now waiting even though a packet has arrived and needs to be processed. When the next packet arrives, the network manager will execute E and F again, and the web server will wake up to find two queued packets. (One might wonder if the network manager would overwrite the first packet with the second one. Since the problem says that the first packet is sometimes handled late, rather than saying it is lost, overwriting must not be a concern.)
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