init: init nachos hw01, should pass jenkins os_group_20_hw job but fail on os_group_20_ta job
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TA
268
code/machine/disk.cc
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268
code/machine/disk.cc
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// disk.cc
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// Routines to simulate a physical disk device; reading and writing
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// to the disk is simulated as reading and writing to a UNIX file.
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// See disk.h for details about the behavior of disks (and
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// therefore about the behavior of this simulation).
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//
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// Disk operations are asynchronous, so we have to invoke an interrupt
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// handler when the simulated operation completes.
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//
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// DO NOT CHANGE -- part of the machine emulation
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//
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// Copyright (c) 1992-1993 The Regents of the University of California.
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// All rights reserved. See copyright.h for copyright notice and limitation
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// of liability and disclaimer of warranty provisions.
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#include "copyright.h"
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#include "disk.h"
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#include "debug.h"
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#include "sysdep.h"
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#include "main.h"
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// We put a magic number at the front of the UNIX file representing the
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// disk, to make it less likely we will accidentally treat a useful file
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// as a disk (which would probably trash the file's contents).
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const int MagicNumber = 0x456789ab;
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const int MagicSize = sizeof(int);
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const int DiskSize = (MagicSize + (NumSectors * SectorSize));
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//----------------------------------------------------------------------
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// Disk::Disk()
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// Initialize a simulated disk. Open the UNIX file (creating it
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// if it doesn't exist), and check the magic number to make sure it's
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// ok to treat it as Nachos disk storage.
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//
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// "toCall" -- object to call when disk read/write request completes
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//----------------------------------------------------------------------
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Disk::Disk(CallBackObj *toCall)
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{
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int magicNum;
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int tmp = 0;
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DEBUG(dbgDisk, "Initializing the disk.");
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callWhenDone = toCall;
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lastSector = 0;
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bufferInit = 0;
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sprintf(diskname,"DISK_%d",kernel->hostName);
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fileno = OpenForReadWrite(diskname, FALSE);
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if (fileno >= 0) { // file exists, check magic number
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Read(fileno, (char *) &magicNum, MagicSize);
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ASSERT(magicNum == MagicNumber);
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} else { // file doesn't exist, create it
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fileno = OpenForWrite(diskname);
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magicNum = MagicNumber;
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WriteFile(fileno, (char *) &magicNum, MagicSize); // write magic number
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// need to write at end of file, so that reads will not return EOF
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Lseek(fileno, DiskSize - sizeof(int), 0);
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WriteFile(fileno, (char *)&tmp, sizeof(int));
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}
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active = FALSE;
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}
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//----------------------------------------------------------------------
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// Disk::~Disk()
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// Clean up disk simulation, by closing the UNIX file representing the
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// disk.
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//----------------------------------------------------------------------
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Disk::~Disk()
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{
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Close(fileno);
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}
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//----------------------------------------------------------------------
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// Disk::PrintSector()
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// Dump the data in a disk read/write request, for debugging.
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//----------------------------------------------------------------------
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static void
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PrintSector (bool writing, int sector, char *data)
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{
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int *p = (int *) data;
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if (writing)
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cout << "Writing sector: " << sector << "\n";
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else
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cout << "Reading sector: " << sector << "\n";
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for (unsigned int i = 0; i < (SectorSize/sizeof(int)); i++) {
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cout << p[i] << " ";
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}
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cout << "\n";
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}
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//----------------------------------------------------------------------
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// Disk::ReadRequest/WriteRequest
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// Simulate a request to read/write a single disk sector
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// Do the read/write immediately to the UNIX file
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// Set up an interrupt handler to be called later,
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// that will notify the caller when the simulator says
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// the operation has completed.
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//
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// Note that a disk only allows an entire sector to be read/written,
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// not part of a sector.
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//
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// "sectorNumber" -- the disk sector to read/write
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// "data" -- the bytes to be written, the buffer to hold the incoming bytes
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//----------------------------------------------------------------------
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void
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Disk::ReadRequest(int sectorNumber, char* data)
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{
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int ticks = ComputeLatency(sectorNumber, FALSE);
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ASSERT(!active); // only one request at a time
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ASSERT((sectorNumber >= 0) && (sectorNumber < NumSectors));
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DEBUG(dbgDisk, "Reading from sector " << sectorNumber);
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Lseek(fileno, SectorSize * sectorNumber + MagicSize, 0);
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Read(fileno, data, SectorSize);
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if (debug->IsEnabled('d'))
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PrintSector(FALSE, sectorNumber, data);
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active = TRUE;
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UpdateLast(sectorNumber);
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kernel->stats->numDiskReads++;
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kernel->interrupt->Schedule(this, ticks, DiskInt);
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}
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void
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Disk::WriteRequest(int sectorNumber, char* data)
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{
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int ticks = ComputeLatency(sectorNumber, TRUE);
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ASSERT(!active);
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ASSERT((sectorNumber >= 0) && (sectorNumber < NumSectors));
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DEBUG(dbgDisk, "Writing to sector " << sectorNumber);
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Lseek(fileno, SectorSize * sectorNumber + MagicSize, 0);
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WriteFile(fileno, data, SectorSize);
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if (debug->IsEnabled('d'))
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PrintSector(TRUE, sectorNumber, data);
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active = TRUE;
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UpdateLast(sectorNumber);
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kernel->stats->numDiskWrites++;
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kernel->interrupt->Schedule(this, ticks, DiskInt);
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}
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//----------------------------------------------------------------------
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// Disk::CallBack()
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// Called by the machine simulation when the disk interrupt occurs.
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//----------------------------------------------------------------------
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void
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Disk::CallBack ()
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{
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active = FALSE;
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callWhenDone->CallBack();
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}
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//----------------------------------------------------------------------
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// Disk::TimeToSeek()
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// Returns how long it will take to position the disk head over the correct
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// track on the disk. Since when we finish seeking, we are likely
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// to be in the middle of a sector that is rotating past the head,
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// we also return how long until the head is at the next sector boundary.
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//
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// Disk seeks at one track per SeekTime ticks (cf. stats.h)
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// and rotates at one sector per RotationTime ticks
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//----------------------------------------------------------------------
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int
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Disk::TimeToSeek(int newSector, int *rotation)
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{
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int newTrack = newSector / SectorsPerTrack;
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int oldTrack = lastSector / SectorsPerTrack;
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int seek = abs(newTrack - oldTrack) * SeekTime;
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// how long will seek take?
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int over = (kernel->stats->totalTicks + seek) % RotationTime;
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// will we be in the middle of a sector when
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// we finish the seek?
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*rotation = 0;
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if (over > 0) // if so, need to round up to next full sector
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*rotation = RotationTime - over;
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return seek;
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}
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//----------------------------------------------------------------------
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// Disk::ModuloDiff()
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// Return number of sectors of rotational delay between target sector
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// "to" and current sector position "from"
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//----------------------------------------------------------------------
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int
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Disk::ModuloDiff(int to, int from)
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{
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int toOffset = to % SectorsPerTrack;
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int fromOffset = from % SectorsPerTrack;
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return ((toOffset - fromOffset) + SectorsPerTrack) % SectorsPerTrack;
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}
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//----------------------------------------------------------------------
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// Disk::ComputeLatency()
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// Return how long will it take to read/write a disk sector, from
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// the current position of the disk head.
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//
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// Latency = seek time + rotational latency + transfer time
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// Disk seeks at one track per SeekTime ticks (cf. stats.h)
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// and rotates at one sector per RotationTime ticks
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//
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// To find the rotational latency, we first must figure out where the
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// disk head will be after the seek (if any). We then figure out
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// how long it will take to rotate completely past newSector after
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// that point.
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//
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// The disk also has a "track buffer"; the disk continuously reads
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// the contents of the current disk track into the buffer. This allows
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// read requests to the current track to be satisfied more quickly.
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// The contents of the track buffer are discarded after every seek to
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// a new track.
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//----------------------------------------------------------------------
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int
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Disk::ComputeLatency(int newSector, bool writing)
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{
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int rotation;
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int seek = TimeToSeek(newSector, &rotation);
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int timeAfter = kernel->stats->totalTicks + seek + rotation;
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#ifndef NOTRACKBUF // turn this on if you don't want the track buffer stuff
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// check if track buffer applies
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if ((writing == FALSE) && (seek == 0)
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&& (((timeAfter - bufferInit) / RotationTime)
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> ModuloDiff(newSector, bufferInit / RotationTime))) {
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DEBUG(dbgDisk, "Request latency = " << RotationTime);
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return RotationTime; // time to transfer sector from the track buffer
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}
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#endif
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rotation += ModuloDiff(newSector, timeAfter / RotationTime) * RotationTime;
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DEBUG(dbgDisk, "Request latency = " << (seek + rotation + RotationTime));
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return(seek + rotation + RotationTime);
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}
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//----------------------------------------------------------------------
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// Disk::UpdateLast
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// Keep track of the most recently requested sector. So we can know
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// what is in the track buffer.
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//----------------------------------------------------------------------
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void
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Disk::UpdateLast(int newSector)
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{
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int rotate;
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int seek = TimeToSeek(newSector, &rotate);
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if (seek != 0)
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bufferInit = kernel->stats->totalTicks + seek + rotate;
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lastSector = newSector;
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DEBUG(dbgDisk, "Updating last sector = " << lastSector << " , " << bufferInit);
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}
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