Btrace无疑是性能调优的一个非常重要的工具,它可以做到代码无侵入性的挖掘性能的问题,它利用字节码级别的运行时动态植入来check性能问题,性能优化的第一步往往是找出性能的瓶颈,如下面的功能是check程序的运行的线程数:
/*
* Copyright 2008-2010 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
package example3;
import static com.sun.btrace.BTraceUtils.println;
import static com.sun.btrace.BTraceUtils.str;
import static com.sun.btrace.BTraceUtils.threadCount;
import java.util.concurrent.atomic.AtomicInteger;
import com.sun.btrace.BTraceUtils.Atomic;
import com.sun.btrace.BTraceUtils.Strings;
import com.sun.btrace.BTraceUtils.Threads;
import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.Export;
import com.sun.btrace.annotations.OnMethod;
import com.sun.btrace.annotations.OnTimer;
import com.sun.btrace.annotations.Self;
/**
* This sample creates a jvmstat counter and
* increments it everytime Thread.start() is
* called. This thread count may be accessed
* from outside the process. The @Export annotated
* fields are mapped to jvmstat counters. The counter
* name is "btrace." + <className> + "." + <fieldName>
*/
@BTrace public class ThreadCounter {
// create a jvmstat counter using @Export
@Export private static AtomicInteger count=new AtomicInteger(0);
@OnMethod(
clazz="java.lang.Thread",
method="start"
)
public static void onnewThread(@Self Thread t) {
// updating counter is easy. Just assign to
// the static field!
println(Strings.strcat("starting ", Threads.name(t)));
Atomic.addAndGet(count, 1);
}
@OnTimer(2000)
public static void ontimer() {
// we can access counter as "count" as well
// as from jvmstat counter directly.
println(Strings.strcat("total thread count:", str(threadCount())));
println(Strings.strcat("start thread count:", str(count)));
}
}
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