The Perf.java Java example source code
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* under the terms of the GNU General Public License version 2 only, as
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package sun.misc;
import java.nio.ByteBuffer;
import java.security.Permission;
import java.security.PrivilegedAction;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
/**
* The Perf class provides the ability to attach to an instrumentation
* buffer maintained by a Java virtual machine. The instrumentation
* buffer may be for the Java virtual machine running the methods of
* this class or it may be for another Java virtual machine on the
* same system.
* <p>
* In addition, this class provides methods to create instrumentation
* objects in the instrumentation buffer for the Java virtual machine
* that is running these methods. It also contains methods for acquiring
* the value of a platform specific high resolution clock for time
* stamp and interval measurement purposes.
*
* @author Brian Doherty
* @since 1.4.2
* @see #getPerf
* @see sun.misc.Perf$GetPerfAction
* @see java.nio.ByteBuffer
*/
public final class Perf {
private static Perf instance;
private static final int PERF_MODE_RO = 0;
private static final int PERF_MODE_RW = 1;
private Perf() { } // prevent instantiation
/**
* The GetPerfAction class is a convenience class for acquiring access
* to the singleton Perf instance using the
* <code>AccessController.doPrivileged() method.
* <p>
* An instance of this class can be used as the argument to
* <code>AccessController.doPrivileged(PrivilegedAction).
* <p> Here is a suggested idiom for use of this class:
*
* <blockquote>
* class MyTrustedClass {
* private static final Perf perf =
* AccessController.doPrivileged(new Perf.GetPerfAction<Perf>());
* ...
* }
* </pre>
* <p>
* In the presence of a security manager, the <code>MyTrustedClass
* class in the above example will need to be granted the
* <em>"sun.misc.Perf.getPerf" RuntimePermission
* permission in order to successfully acquire the singleton Perf instance.
* <p>
* Please note that the <em>"sun.misc.Perf.getPerf" permission
* is not a JDK specified permission.
*
* @see java.security.AccessController#doPrivileged(PrivilegedAction)
* @see java.lang.RuntimePermission
*/
public static class GetPerfAction implements PrivilegedAction<Perf>
{
/**
* Run the <code>Perf.getPerf() method in a privileged context.
*
* @see #getPerf
*/
public Perf run() {
return getPerf();
}
}
/**
* Return a reference to the singleton Perf instance.
* <p>
* The getPerf() method returns the singleton instance of the Perf
* class. The returned object provides the caller with the capability
* for accessing the instrumentation buffer for this or another local
* Java virtual machine.
* <p>
* If a security manager is installed, its <code>checkPermission
* method is called with a <code>RuntimePermission with a target
* of <em>"sun.misc.Perf.getPerf". A security exception will result
* if the caller has not been granted this permission.
* <p>
* Access to the returned <code>Perf object should be protected
* by its caller and not passed on to untrusted code. This object can
* be used to attach to the instrumentation buffer provided by this Java
* virtual machine or for those of other Java virtual machines running
* on the same system. The instrumentation buffer may contain senstitive
* information. API's built on top of this interface may want to provide
* finer grained access control to the contents of individual
* instrumentation objects contained within the buffer.
* <p>
* Please note that the <em>"sun.misc.Perf.getPerf" permission
* is not a JDK specified permission.
*
* @return A reference to the singleton Perf instance.
* @throws AccessControlException if a security manager exists and
* its <code>checkPermission method doesn't allow
* access to the <em>"sun.misc.Perf.getPerf" target.
* @see java.lang.RuntimePermission
* @see #attach
*/
public static Perf getPerf()
{
SecurityManager security = System.getSecurityManager();
if (security != null) {
Permission perm = new RuntimePermission("sun.misc.Perf.getPerf");
security.checkPermission(perm);
}
return instance;
}
/**
* Attach to the instrumentation buffer for the specified Java virtual
* machine.
* <p>
* This method will attach to the instrumentation buffer for the
* specified virtual machine. It returns a <code>ByteBuffer object
* that is initialized to access the instrumentation buffer for the
* indicated Java virtual machine. The <code>lvmid parameter is
* a integer value that uniquely identifies the target local Java virtual
* machine. It is typically, but not necessarily, the process id of
* the target Java virtual machine.
* <p>
* If the <code>lvmid identifies a Java virtual machine different
* from the one running this method, then the coherency characteristics
* of the buffer are implementation dependent. Implementations that do
* not support named, coherent, shared memory may return a
* <code>ByteBuffer object that contains only a snap shot of the
* data in the instrumentation buffer. Implementations that support named,
* coherent, shared memory, may return a <code>ByteBuffer object
* that will be changing dynamically over time as the target Java virtual
* machine updates its mapping of this buffer.
* <p>
* If the <code>lvmid is 0 or equal to the actual lvmid
* for the Java virtual machine running this method, then the returned
* <code>ByteBuffer object will always be coherent and dynamically
* changing.
* <p>
* The attach mode specifies the access permissions requested for the
* instrumentation buffer of the target virtual machine. The permitted
* access permissions are:
* <p>
* <bl>
* <li>"r" - Read only access. This Java virtual machine has only
* read access to the instrumentation buffer for the target Java
* virtual machine.
* <li>"rw" - Read/Write access. This Java virtual machine has read and
* write access to the instrumentation buffer for the target Java virtual
* machine. This mode is currently not supported and is reserved for
* future enhancements.
* </bl>
*
* @param lvmid an integer that uniquely identifies the
* target local Java virtual machine.
* @param mode a string indicating the attach mode.
* @return ByteBuffer a direct allocated byte buffer
* @throws IllegalArgumentException The lvmid or mode was invalid.
* @throws IOException An I/O error occurred while trying to acquire
* the instrumentation buffer.
* @throws OutOfMemoryError The instrumentation buffer could not be mapped
* into the virtual machine's address space.
* @see java.nio.ByteBuffer
*/
public ByteBuffer attach(int lvmid, String mode)
throws IllegalArgumentException, IOException
{
if (mode.compareTo("r") == 0) {
return attachImpl(null, lvmid, PERF_MODE_RO);
}
else if (mode.compareTo("rw") == 0) {
return attachImpl(null, lvmid, PERF_MODE_RW);
}
else {
throw new IllegalArgumentException("unknown mode");
}
}
/**
* Attach to the instrumentation buffer for the specified Java virtual
* machine owned by the given user.
* <p>
* This method behaves just as the <code>attach(int lvmid, String mode)
* </code> method, except that it only searches for Java virtual machines
* owned by the specified user.
*
* @param user A <code>String object containing the
* name of the user that owns the target Java
* virtual machine.
* @param lvmid an integer that uniquely identifies the
* target local Java virtual machine.
* @param mode a string indicating the attach mode.
* @return ByteBuffer a direct allocated byte buffer
* @throws IllegalArgumentException The lvmid or mode was invalid.
* @throws IOException An I/O error occurred while trying to acquire
* the instrumentation buffer.
* @throws OutOfMemoryError The instrumentation buffer could not be mapped
* into the virtual machine's address space.
* @see java.nio.ByteBuffer
*/
public ByteBuffer attach(String user, int lvmid, String mode)
throws IllegalArgumentException, IOException
{
if (mode.compareTo("r") == 0) {
return attachImpl(user, lvmid, PERF_MODE_RO);
}
else if (mode.compareTo("rw") == 0) {
return attachImpl(user, lvmid, PERF_MODE_RW);
}
else {
throw new IllegalArgumentException("unknown mode");
}
}
/**
* Call the implementation specific attach method.
* <p>
* This method calls into the Java virtual machine to perform the platform
* specific attach method. Buffers returned from this method are
* internally managed as <code>PhantomRefereces to provide for
* guaranteed, secure release of the native resources.
*
* @param user A <code>String object containing the
* name of the user that owns the target Java
* virtual machine.
* @param lvmid an integer that uniquely identifies the
* target local Java virtual machine.
* @param mode a string indicating the attach mode.
* @return ByteBuffer a direct allocated byte buffer
* @throws IllegalArgumentException The lvmid or mode was invalid.
* @throws IOException An I/O error occurred while trying to acquire
* the instrumentation buffer.
* @throws OutOfMemoryError The instrumentation buffer could not be mapped
* into the virtual machine's address space.
*/
private ByteBuffer attachImpl(String user, int lvmid, int mode)
throws IllegalArgumentException, IOException
{
final ByteBuffer b = attach(user, lvmid, mode);
if (lvmid == 0) {
// The native instrumentation buffer for this Java virtual
// machine is never unmapped.
return b;
}
else {
// This is an instrumentation buffer for another Java virtual
// machine with native resources that need to be managed. We
// create a duplicate of the native ByteBuffer and manage it
// with a Cleaner object (PhantomReference). When the duplicate
// becomes only phantomly reachable, the native resources will
// be released.
final ByteBuffer dup = b.duplicate();
Cleaner.create(dup, new Runnable() {
public void run() {
try {
instance.detach(b);
}
catch (Throwable th) {
// avoid crashing the reference handler thread,
// but provide for some diagnosability
assert false : th.toString();
}
}
});
return dup;
}
}
/**
* Native method to perform the implementation specific attach mechanism.
* <p>
* The implementation of this method may return distinct or identical
* <code>ByteBuffer objects for two distinct calls requesting
* attachment to the same Java virtual machine.
* <p>
* For the Sun HotSpot JVM, two distinct calls to attach to the same
* target Java virtual machine will result in two distinct ByteBuffer
* objects returned by this method. This may change in a future release.
*
* @param user A <code>String object containing the
* name of the user that owns the target Java
* virtual machine.
* @param lvmid an integer that uniquely identifies the
* target local Java virtual machine.
* @param mode a string indicating the attach mode.
* @return ByteBuffer a direct allocated byte buffer
* @throws IllegalArgumentException The lvmid or mode was invalid.
* @throws IOException An I/O error occurred while trying to acquire
* the instrumentation buffer.
* @throws OutOfMemoryError The instrumentation buffer could not be mapped
* into the virtual machine's address space.
*/
private native ByteBuffer attach(String user, int lvmid, int mode)
throws IllegalArgumentException, IOException;
/**
* Native method to perform the implementation specific detach mechanism.
* <p>
* If this method is passed a <code>ByteBuffer object that is
* not created by the <code>attach method, then the results of
* this method are undefined, with unpredictable and potentially damaging
* effects to the Java virtual machine. To prevent accidental or malicious
* use of this method, all native ByteBuffer created by the <code>
* attach</code> method are managed internally as PhantomReferences
* and resources are freed by the system.
* <p>
* If this method is passed a <code>ByteBuffer object created
* by the <code>attach method with a lvmid for the Java virtual
* machine running this method (lvmid=0, for example), then the detach
* request is silently ignored.
*
* @param ByteBuffer A direct allocated byte buffer created by the
* <code>attach method.
* @see java.nio.ByteBuffer
* @see #attach
*/
private native void detach(ByteBuffer bb);
/**
* Create a <code>long scalar entry in the instrumentation buffer
* with the given variability characteristic, units, and initial value.
* <p>
* Access to the instrument is provided through the returned <code>
* ByteBuffer</code> object. Typically, this object should be wrapped
* with <code>LongBuffer view object.
*
* @param variability the variability characteristic for this entry.
* @param units the units for this entry.
* @param name the name of this entry.
* @param value the initial value for this entry.
* @return ByteBuffer a direct allocated ByteBuffer object that
* allows write access to a native memory location
* containing a <code>long value.
*
* see sun.misc.perf.Variability
* see sun.misc.perf.Units
* @see java.nio.ByteBuffer
*/
public native ByteBuffer createLong(String name, int variability,
int units, long value);
/**
* Create a <code>String entry in the instrumentation buffer with
* the given variability characteristic, units, and initial value.
* <p>
* The maximum length of the <code>String stored in this string
* instrument is given in by <code>maxLength parameter. Updates
* to this instrument with <code>String values with lengths greater
* than <code>maxLength will be truncated to maxLength.
* The truncated value will be terminated by a null character.
* <p>
* The underlying implementation may further limit the length of the
* value, but will continue to preserve the null terminator.
* <p>
* Access to the instrument is provided through the returned <code>
* ByteBuffer</code> object.
*
* @param variability the variability characteristic for this entry.
* @param units the units for this entry.
* @param name the name of this entry.
* @param value the initial value for this entry.
* @param maxLength the maximum string length for this string
* instrument.
* @return ByteBuffer a direct allocated ByteBuffer that allows
* write access to a native memory location
* containing a <code>long value.
*
* see sun.misc.perf.Variability
* see sun.misc.perf.Units
* @see java.nio.ByteBuffer
*/
public ByteBuffer createString(String name, int variability,
int units, String value, int maxLength)
{
byte[] v = getBytes(value);
byte[] v1 = new byte[v.length+1];
System.arraycopy(v, 0, v1, 0, v.length);
v1[v.length] = '\0';
return createByteArray(name, variability, units, v1, Math.max(v1.length, maxLength));
}
/**
* Create a <code>String entry in the instrumentation buffer with
* the given variability characteristic, units, and initial value.
* <p>
* The maximum length of the <code>String stored in this string
* instrument is implied by the length of the <code>value parameter.
* Subsequent updates to the value of this instrument will be truncated
* to this implied maximum length. The truncated value will be terminated
* by a null character.
* <p>
* The underlying implementation may further limit the length of the
* initial or subsequent value, but will continue to preserve the null
* terminator.
* <p>
* Access to the instrument is provided through the returned <code>
* ByteBuffer</code> object.
*
* @param variability the variability characteristic for this entry.
* @param units the units for this entry.
* @param name the name of this entry.
* @param value the initial value for this entry.
* @return ByteBuffer a direct allocated ByteBuffer that allows
* write access to a native memory location
* containing a <code>long value.
*
* see sun.misc.perf.Variability
* see sun.misc.perf.Units
* @see java.nio.ByteBuffer
*/
public ByteBuffer createString(String name, int variability,
int units, String value)
{
byte[] v = getBytes(value);
byte[] v1 = new byte[v.length+1];
System.arraycopy(v, 0, v1, 0, v.length);
v1[v.length] = '\0';
return createByteArray(name, variability, units, v1, v1.length);
}
/**
* Create a <code>byte vector entry in the instrumentation buffer
* with the given variability characteristic, units, and initial value.
* <p>
* The <code>maxLength parameter limits the size of the byte
* array instrument such that the initial or subsequent updates beyond
* this length are silently ignored. No special handling of truncated
* updates is provided.
* <p>
* The underlying implementation may further limit the length of the
* length of the initial or subsequent value.
* <p>
* Access to the instrument is provided through the returned <code>
* ByteBuffer</code> object.
*
* @param variability the variability characteristic for this entry.
* @param units the units for this entry.
* @param name the name of this entry.
* @param value the initial value for this entry.
* @param maxLength the maximum length of this byte array.
* @return ByteBuffer a direct allocated byte buffer that allows
* write access to a native memory location
* containing a <code>long value.
*
* see sun.misc.perf.Variability
* see sun.misc.perf.Units
* @see java.nio.ByteBuffer
*/
public native ByteBuffer createByteArray(String name, int variability,
int units, byte[] value,
int maxLength);
/**
* convert string to an array of UTF-8 bytes
*/
private static byte[] getBytes(String s)
{
byte[] bytes = null;
try {
bytes = s.getBytes("UTF-8");
}
catch (UnsupportedEncodingException e) {
// ignore, UTF-8 encoding is always known
}
return bytes;
}
/**
* Return the value of the High Resolution Counter.
*
* The High Resolution Counter returns the number of ticks since
* since the start of the Java virtual machine. The resolution of
* the counter is machine dependent and can be determined from the
* value return by the {@link #highResFrequency} method.
*
* @return the number of ticks of machine dependent resolution since
* the start of the Java virtual machine.
*
* @see #highResFrequency
* @see java.lang.System#currentTimeMillis()
*/
public native long highResCounter();
/**
* Returns the frequency of the High Resolution Counter, in ticks per
* second.
*
* This value can be used to convert the value of the High Resolution
* Counter, as returned from a call to the {@link #highResCounter} method,
* into the number of seconds since the start of the Java virtual machine.
*
* @return the frequency of the High Resolution Counter.
* @see #highResCounter
*/
public native long highResFrequency();
private static native void registerNatives();
static {
registerNatives();
instance = new Perf();
}
}
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