50 * @see java.nio.ByteBuffer
51 */
52 public final class Perf {
53
54 private static Perf instance;
55
56 private static final int PERF_MODE_RO = 0;
57 private static final int PERF_MODE_RW = 1;
58
59 private Perf() { } // prevent instantiation
60
61 /**
62 * The GetPerfAction class is a convenience class for acquiring access
63 * to the singleton Perf instance using the
64 * <code>AccessController.doPrivileged()</code> method.
65 * <p>
66 * An instance of this class can be used as the argument to
67 * <code>AccessController.doPrivileged(PrivilegedAction)</code>.
68 * <p> Here is a suggested idiom for use of this class:
69 *
70 * <blockquote><pre>
71 * class MyTrustedClass {
72 * private static final Perf perf =
73 * AccessController.doPrivileged(new Perf.GetPerfAction<Perf>());
74 * ...
75 * }
76 * </pre></blockquote>
77 * <p>
78 * In the presence of a security manager, the <code>MyTrustedClass</code>
79 * class in the above example will need to be granted the
80 * <em>"sun.misc.Perf.getPerf"</em> <code>RuntimePermission</code>
81 * permission in order to successfully acquire the singleton Perf instance.
82 * <p>
83 * Please note that the <em>"sun.misc.Perf.getPerf"</em> permission
84 * is not a JDK specified permission.
85 *
86 * @see java.security.AccessController#doPrivileged(PrivilegedAction)
87 * @see java.lang.RuntimePermission
88 */
89 public static class GetPerfAction implements PrivilegedAction<Perf>
90 {
91 /**
92 * Run the <code>Perf.getPerf()</code> method in a privileged context.
93 *
94 * @see #getPerf
95 */
96 public Perf run() {
154 * the target Java virtual machine.
155 * <p>
156 * If the <code>lvmid</code> identifies a Java virtual machine different
157 * from the one running this method, then the coherency characteristics
158 * of the buffer are implementation dependent. Implementations that do
159 * not support named, coherent, shared memory may return a
160 * <code>ByteBuffer</code> object that contains only a snap shot of the
161 * data in the instrumentation buffer. Implementations that support named,
162 * coherent, shared memory, may return a <code>ByteBuffer</code> object
163 * that will be changing dynamically over time as the target Java virtual
164 * machine updates its mapping of this buffer.
165 * <p>
166 * If the <code>lvmid</code> is 0 or equal to the actual <code>lvmid</code>
167 * for the Java virtual machine running this method, then the returned
168 * <code>ByteBuffer</code> object will always be coherent and dynamically
169 * changing.
170 * <p>
171 * The attach mode specifies the access permissions requested for the
172 * instrumentation buffer of the target virtual machine. The permitted
173 * access permissions are:
174 * <p>
175 * <bl>
176 * <li>"r" - Read only access. This Java virtual machine has only
177 * read access to the instrumentation buffer for the target Java
178 * virtual machine.
179 * <li>"rw" - Read/Write access. This Java virtual machine has read and
180 * write access to the instrumentation buffer for the target Java virtual
181 * machine. This mode is currently not supported and is reserved for
182 * future enhancements.
183 * </bl>
184 *
185 * @param lvmid an integer that uniquely identifies the
186 * target local Java virtual machine.
187 * @param mode a string indicating the attach mode.
188 * @return ByteBuffer a direct allocated byte buffer
189 * @throws IllegalArgumentException The lvmid or mode was invalid.
190 * @throws IOException An I/O error occurred while trying to acquire
191 * the instrumentation buffer.
192 * @throws OutOfMemoryError The instrumentation buffer could not be mapped
193 * into the virtual machine's address space.
194 * @see java.nio.ByteBuffer
195 */
196 public ByteBuffer attach(int lvmid, String mode)
197 throws IllegalArgumentException, IOException
198 {
199 if (mode.compareTo("r") == 0) {
200 return attachImpl(null, lvmid, PERF_MODE_RO);
201 }
202 else if (mode.compareTo("rw") == 0) {
203 return attachImpl(null, lvmid, PERF_MODE_RW);
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50 * @see java.nio.ByteBuffer
51 */
52 public final class Perf {
53
54 private static Perf instance;
55
56 private static final int PERF_MODE_RO = 0;
57 private static final int PERF_MODE_RW = 1;
58
59 private Perf() { } // prevent instantiation
60
61 /**
62 * The GetPerfAction class is a convenience class for acquiring access
63 * to the singleton Perf instance using the
64 * <code>AccessController.doPrivileged()</code> method.
65 * <p>
66 * An instance of this class can be used as the argument to
67 * <code>AccessController.doPrivileged(PrivilegedAction)</code>.
68 * <p> Here is a suggested idiom for use of this class:
69 *
70 * <blockquote><pre>{@code
71 * class MyTrustedClass {
72 * private static final Perf perf =
73 * AccessController.doPrivileged(new Perf.GetPerfAction<Perf>());
74 * ...
75 * }
76 * }</pre></blockquote>
77 * <p>
78 * In the presence of a security manager, the <code>MyTrustedClass</code>
79 * class in the above example will need to be granted the
80 * <em>"sun.misc.Perf.getPerf"</em> <code>RuntimePermission</code>
81 * permission in order to successfully acquire the singleton Perf instance.
82 * <p>
83 * Please note that the <em>"sun.misc.Perf.getPerf"</em> permission
84 * is not a JDK specified permission.
85 *
86 * @see java.security.AccessController#doPrivileged(PrivilegedAction)
87 * @see java.lang.RuntimePermission
88 */
89 public static class GetPerfAction implements PrivilegedAction<Perf>
90 {
91 /**
92 * Run the <code>Perf.getPerf()</code> method in a privileged context.
93 *
94 * @see #getPerf
95 */
96 public Perf run() {
154 * the target Java virtual machine.
155 * <p>
156 * If the <code>lvmid</code> identifies a Java virtual machine different
157 * from the one running this method, then the coherency characteristics
158 * of the buffer are implementation dependent. Implementations that do
159 * not support named, coherent, shared memory may return a
160 * <code>ByteBuffer</code> object that contains only a snap shot of the
161 * data in the instrumentation buffer. Implementations that support named,
162 * coherent, shared memory, may return a <code>ByteBuffer</code> object
163 * that will be changing dynamically over time as the target Java virtual
164 * machine updates its mapping of this buffer.
165 * <p>
166 * If the <code>lvmid</code> is 0 or equal to the actual <code>lvmid</code>
167 * for the Java virtual machine running this method, then the returned
168 * <code>ByteBuffer</code> object will always be coherent and dynamically
169 * changing.
170 * <p>
171 * The attach mode specifies the access permissions requested for the
172 * instrumentation buffer of the target virtual machine. The permitted
173 * access permissions are:
174 * <ul>
175 * <li>"r" - Read only access. This Java virtual machine has only
176 * read access to the instrumentation buffer for the target Java
177 * virtual machine.
178 * <li>"rw" - Read/Write access. This Java virtual machine has read and
179 * write access to the instrumentation buffer for the target Java virtual
180 * machine. This mode is currently not supported and is reserved for
181 * future enhancements.
182 * </ul>
183 *
184 * @param lvmid an integer that uniquely identifies the
185 * target local Java virtual machine.
186 * @param mode a string indicating the attach mode.
187 * @return ByteBuffer a direct allocated byte buffer
188 * @throws IllegalArgumentException The lvmid or mode was invalid.
189 * @throws IOException An I/O error occurred while trying to acquire
190 * the instrumentation buffer.
191 * @throws OutOfMemoryError The instrumentation buffer could not be mapped
192 * into the virtual machine's address space.
193 * @see java.nio.ByteBuffer
194 */
195 public ByteBuffer attach(int lvmid, String mode)
196 throws IllegalArgumentException, IOException
197 {
198 if (mode.compareTo("r") == 0) {
199 return attachImpl(null, lvmid, PERF_MODE_RO);
200 }
201 else if (mode.compareTo("rw") == 0) {
202 return attachImpl(null, lvmid, PERF_MODE_RW);
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