/**
* The caller specifies the region of virtual memory to be used for this space. If this region
* conflicts with an existing space, then the constructor will fail.
*
* @param name The name of this space (used when printing error messages etc)
* @param pageBudget The number of pages this space may consume before consulting the plan
* @param vmRequest An object describing the virtual memory requested.
*/
public LargeObjectSpace(String name, int pageBudget, VMRequest vmRequest) {
super(name, pageBudget, vmRequest);
treadmill = new Treadmill(LOG_BYTES_IN_PAGE, true);
markState = Word.zero();
}
/**
* Low level copy of <code>copyBytes</code> bytes from <code>src[srcPos]</code> to <code>
* dst[dstPos]</code>.
*
* <p>Assumption: <code>src != dst || (srcPos >= dstPos)</code> and element size is 2 bytes.
*
* @param dstPtr The destination start address
* @param srcPtr The source start address
* @param copyBytes The number of bytes to be copied
*/
public static void aligned16Copy(Address dstPtr, Address srcPtr, int copyBytes) {
if (USE_NATIVE && copyBytes > NATIVE_THRESHOLD) {
memcopy(dstPtr, srcPtr, copyBytes);
} else {
if (copyBytes >= BYTES_IN_COPY
&& (srcPtr.toWord().and(Word.fromIntZeroExtend(BYTES_IN_COPY - 1))
== (dstPtr.toWord().and(Word.fromIntZeroExtend(BYTES_IN_COPY - 1))))) {
// relative alignment is the same
Address endPtr = srcPtr.plus(copyBytes);
Address wordEndPtr =
endPtr.toWord().and(Word.fromIntZeroExtend(BYTES_IN_COPY - 1).not()).toAddress();
if (BYTES_IN_COPY == 8) {
if (srcPtr.toWord().and(Word.fromIntZeroExtend(2)).NE(Word.zero())) {
copy2Bytes(dstPtr, srcPtr);
srcPtr = srcPtr.plus(2);
dstPtr = dstPtr.plus(2);
}
if (srcPtr.toWord().and(Word.fromIntZeroExtend(4)).NE(Word.zero())) {
copy4Bytes(dstPtr, srcPtr);
srcPtr = srcPtr.plus(4);
dstPtr = dstPtr.plus(4);
}
} else {
if (srcPtr.toWord().and(Word.fromIntZeroExtend(2)).NE(Word.zero())) {
copy2Bytes(dstPtr, srcPtr);
srcPtr = srcPtr.plus(2);
dstPtr = dstPtr.plus(2);
}
}
while (srcPtr.LT(wordEndPtr)) {
if (BYTES_IN_COPY == 8) {
copy8Bytes(dstPtr, srcPtr);
} else {
copy4Bytes(dstPtr, srcPtr);
}
srcPtr = srcPtr.plus(BYTES_IN_COPY);
dstPtr = dstPtr.plus(BYTES_IN_COPY);
}
// if(VM.VerifyAssertions) VM._assert(wordEndPtr.EQ(srcPtr));
if (BYTES_IN_COPY == 8) {
if (endPtr.toWord().and(Word.fromIntZeroExtend(4)).NE(Word.zero())) {
copy4Bytes(dstPtr, srcPtr);
srcPtr = srcPtr.plus(4);
dstPtr = dstPtr.plus(4);
}
if (endPtr.toWord().and(Word.fromIntZeroExtend(2)).NE(Word.zero())) {
copy2Bytes(dstPtr, srcPtr);
}
} else {
if (endPtr.toWord().and(Word.fromIntZeroExtend(2)).NE(Word.zero())) {
copy2Bytes(dstPtr, srcPtr);
}
}
} else {
Address endPtr = srcPtr.plus(copyBytes);
while (srcPtr.LT(endPtr)) {
copy2Bytes(dstPtr, srcPtr);
srcPtr = srcPtr.plus(2);
dstPtr = dstPtr.plus(2);
}
}
}
}
/**
* This class implements tracing for a simple immortal collection policy. Under this policy all that
* is required is for the "collector" to propogate marks in a liveness trace. It does not actually
* collect. This class does not hold any state, all methods are static.
*
* <p>$Id: ImmortalSpace.java,v 1.18 2005/01/19 02:49:02 steveb-oss Exp $
*
* @author Perry Cheng
* @author <a href="http://cs.anu.edu.au/~Steve.Blackburn">Steve Blackburn</a>
* @version $Revision: 1.18 $
* @date $Date: 2005/01/19 02:49:02 $
*/
public final class ImmortalSpace extends Space implements Constants, Uninterruptible {
/**
* **************************************************************************
*
* <p>Class variables
*/
static final Word GC_MARK_BIT_MASK = Word.one();
public static Word immortalMarkState = Word.zero(); // when GC off, the initialization value
/**
* **************************************************************************
*
* <p>Initialization
*/
/**
* The caller specifies the region of virtual memory to be used for this space. If this region
* conflicts with an existing space, then the constructor will fail.
*
* @param name The name of this space (used when printing error messages etc)
* @param pageBudget The number of pages this space may consume before consulting the plan
* @param start The start address of the space in virtual memory
* @param bytes The size of the space in virtual memory, in bytes
*/
public ImmortalSpace(String name, int pageBudget, Address start, Extent bytes) {
super(name, false, true, start, bytes);
pr = new MonotonePageResource(pageBudget, this, start, extent);
}
/**
* Construct a space of a given number of megabytes in size.
*
* <p>The caller specifies the amount virtual memory to be used for this space <i>in
* megabytes</i>. If there is insufficient address space, then the constructor will fail.
*
* @param name The name of this space (used when printing error messages etc)
* @param pageBudget The number of pages this space may consume before consulting the plan
* @param mb The size of the space in virtual memory, in megabytes (MB)
*/
public ImmortalSpace(String name, int pageBudget, int mb) {
super(name, false, true, mb);
pr = new MonotonePageResource(pageBudget, this, start, extent);
}
/**
* Construct a space that consumes a given fraction of the available virtual memory.
*
* <p>The caller specifies the amount virtual memory to be used for this space <i>as a fraction of
* the total available</i>. If there is insufficient address space, then the constructor will
* fail.
*
* @param name The name of this space (used when printing error messages etc)
* @param pageBudget The number of pages this space may consume before consulting the plan
* @param frac The size of the space in virtual memory, as a fraction of all available virtual
* memory
*/
public ImmortalSpace(String name, int pageBudget, float frac) {
super(name, false, true, frac);
pr = new MonotonePageResource(pageBudget, this, start, extent);
}
/**
* Construct a space that consumes a given number of megabytes of virtual memory, at either the
* top or bottom of the available virtual memory.
*
* <p>The caller specifies the amount virtual memory to be used for this space <i>in
* megabytes</i>, and whether it should be at the top or bottom of the available virtual memory.
* If the request clashes with existing virtual memory allocations, then the constructor will
* fail.
*
* @param name The name of this space (used when printing error messages etc)
* @param pageBudget The number of pages this space may consume before consulting the plan
* @param mb The size of the space in virtual memory, in megabytes (MB)
* @param top Should this space be at the top (or bottom) of the available virtual memory.
*/
public ImmortalSpace(String name, int pageBudget, int mb, boolean top) {
super(name, false, true, mb, top);
pr = new MonotonePageResource(pageBudget, this, start, extent);
}
/**
* Construct a space that consumes a given fraction of the available virtual memory, at either the
* top or bottom of the available virtual memory.
*
* <p>The caller specifies the amount virtual memory to be used for this space <i>as a fraction of
* the total available</i>, and whether it should be at the top or bottom of the available virtual
* memory. If the request clashes with existing virtual memory allocations, then the constructor
* will fail.
*
* @param name The name of this space (used when printing error messages etc)
* @param pageBudget The number of pages this space may consume before consulting the plan
* @param frac The size of the space in virtual memory, as a fraction of all available virtual
* memory
* @param top Should this space be at the top (or bottom) of the available virtual memory.
*/
public ImmortalSpace(String name, int pageBudget, float frac, boolean top) {
super(name, false, true, frac, top);
pr = new MonotonePageResource(pageBudget, this, start, extent);
}
/**
* **************************************************************************
*
* <p>Object header manipulations
*/
/** test to see if the mark bit has the given value */
private static boolean testMarkBit(ObjectReference object, Word value) {
return !(ObjectModel.readAvailableBitsWord(object).and(value).isZero());
}
/** write the given value in the mark bit. */
private static void writeMarkBit(ObjectReference object, Word value) {
Word oldValue = ObjectModel.readAvailableBitsWord(object);
Word newValue = oldValue.and(GC_MARK_BIT_MASK.not()).or(value);
ObjectModel.writeAvailableBitsWord(object, newValue);
}
/** atomically write the given value in the mark bit. */
private static void atomicWriteMarkBit(ObjectReference object, Word value) {
while (true) {
Word oldValue = ObjectModel.prepareAvailableBits(object);
Word newValue = oldValue.and(GC_MARK_BIT_MASK.not()).or(value);
if (ObjectModel.attemptAvailableBits(object, oldValue, newValue)) break;
}
}
/**
* Used to mark boot image objects during a parallel scan of objects during GC Returns true if
* marking was done.
*/
private static boolean testAndMark(ObjectReference object, Word value) throws InlinePragma {
Word oldValue;
do {
oldValue = ObjectModel.prepareAvailableBits(object);
Word markBit = oldValue.and(GC_MARK_BIT_MASK);
if (markBit.EQ(value)) return false;
} while (!ObjectModel.attemptAvailableBits(object, oldValue, oldValue.xor(GC_MARK_BIT_MASK)));
return true;
}
/**
* Trace a reference to an object under an immortal collection policy. If the object is not
* already marked, enqueue the object for subsequent processing. The object is marked as (an
* atomic) side-effect of checking whether already marked.
*
* @param object The object to be traced.
*/
public final ObjectReference traceObject(ObjectReference object) throws InlinePragma {
if (testAndMark(object, immortalMarkState)) Plan.enqueue(object);
return object;
}
public static void postAlloc(ObjectReference object) throws InlinePragma {
writeMarkBit(object, immortalMarkState);
}
/**
* Prepare for a new collection increment. For the immortal collector we must flip the state of
* the mark bit between collections.
*/
public void prepare() {
immortalMarkState = GC_MARK_BIT_MASK.sub(immortalMarkState);
}
public void release() {}
/**
* Release an allocated page or pages. In this case we do nothing because we only release pages
* enmasse.
*
* @param start The address of the start of the page or pages
*/
public final void release(Address start) throws InlinePragma {
Assert._assert(false); // this policy only releases pages enmasse
}
public final boolean isLive(ObjectReference object) throws InlinePragma {
return true;
}
/**
* Returns if the object in question is currently thought to be reachable. This is done by
* comparing the mark bit to the current mark state. For the immortal collector reachable and live
* are different, making this method necessary.
*
* @param object The address of an object in immortal space to test
* @return True if <code>ref</code> may be a reachable object (e.g., having the current mark
* state). While all immortal objects are live, some may be unreachable.
*/
public static boolean isReachable(ObjectReference object) {
return (ObjectModel.readAvailableBitsWord(object).and(GC_MARK_BIT_MASK).EQ(immortalMarkState));
}
}
/**
* Gets all of the flags of the given object.
*
* @param object
* @return the object flags
*/
public static Word getObjectFlags(Object object) {
return Word.zero();
}
