csci3753

CSCI3753 Coursework
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pager-basic.c (989B)

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// Very basic pageit algorithm, only allows one process at a time, and one page
// in memory

#include "../common/simulator.h"

void pageit(Pentry q[MAXPROCESSES]) {
  for (int proc = 0; proc < MAXPROCESSES; proc++) {
    if (q[proc].active != 1)
      continue; // select only active processes

    int pc = q[proc].pc;      // program counter for process
    int page = pc / PAGESIZE; // current page the PC is on

    if (q[proc].pages[page])
      break; // if the page is already in memory, then we're done
    if (pagein(proc, page))
      break; // if not in memory, then page it in

    for (int vic = 0;
         vic++ < MAXPROCPAGES;) { // if the pagein fails, find pages to pageout
      if (q[proc].pages[page] != 1)
        continue; // only interested in pages that are in memory
      if (vic == page)
        continue; // make sure the incoming page isn't considered
      if (pageout(proc, vic) == 1)
        break; // page it out and we're done if successful
    }
  }
}