[Картинка: any2fbimgloader3]. Finally, recall that one of the problems with the centralized algorithm is that making it handle all requests can lead to a bottleneck. In the distributed algorithm,all processes are involved inall decisions concerning entry into critical regions. If one process is unable to handle the load, it is unlikely that forcing everyone to do exactly the same thing in parallel is going to help much.. Once again the messenger gets through and delivers the acknowledgement. But now Bonaparte worries that Alexander does not know if the acknowledgement got through. He reasons that if Bonaparte thinks that the messenger was captured, he will not be sure about his (Alexander’s) plans, and may not risk the attack, so he sends the messenger back again.. 1. What is the difference between a file service using the upload/download model and one using the remote access model?. Fig. 6-6. (a) Three clusters connected by an intercluster bus to form one supercluster. (b) Two superclusters connected by a supercluster bus.. 6.4.4. Achieving Sequential Consistency. After passing the barrier, process 1 might start off, storing intoa. Then process 2 might try to store intoa, causing a page fault to fetch the page containing the array. After that, process 1 might try to store intoa, causing another fault, and so on. With a little bad luck, each of the stores might require a full page to be transferred, generating a great deal of traffic. . Fig. 7-1. The Amoeba system architecture.. Group communication also uses FLIP. When a message is sent to multiple destinations, FLIP uses the hardware multicast or broadcast on those networks where it is available. On those that do not have it, broadcast is simulated by sending individual messages, just as we saw on the wide-area network. The choice of mechanism is done by the FLIP layer, with the same user semantics in all cases.. Mach can be configured to do affinity scheduling, but generally this option is off. When it is on, the kernel schedules a thread on the CPU it last ran on, in lopes that part of its address space is still in that CPU’s cache. Affinity scheduling is only applicable to multiprocessors.. The first one,allocate, creates a new port and enters its capability into the caller’s capability list. The capability is for reading from the port. A capability name is returned so that the port can be used.. 9.1.3. System Structure. The synchronization operations are given in Fig. 9-10. Calls are provided for initializing, acquiring, and releasing both mutexes and semaphores. These all work in the usual way.. Fig. 9-25. Context spaces and clusters.. Unlike most systems, in which the current time is simply a binary number, in DTS all times are recorded as intervals. When asked what the time is, instead of saying that it is 9:52, DTS might say it is somewhere between 9:51 and 9:53 (grossly exaggerated). Using intervals instead of values allows DTS to provide the user with a precise specification of how far off the clock might be..