如何提高ThreadLocal封装的SimpleDateFormat的性能？
如何提高ThreadLocal封装的SimpleDateFormat的性能？
提问于 2014-02-28 23:14:24
这是在具有24核的RHEL上的Java7 (51)上的。我们注意到，随着线程池大小的增加，包装在本地线程中的Java SimpleDateFormat的平均响应时间也在增加。这是意料之中的吗？或者，我只是在做一些愚蠢的事情？
测试程序
public class DateFormatterLoadTest {
private static final Logger LOG = Logger.getLogger(DateFormatterLoadTest .class);
private final static int CONCURRENCY = 10;
public static void main(String[] args) throws Exception {
final AtomicLong total = new AtomicLong(0);
ExecutorService es = Executors.newFixedThreadPool(CONCURRENCY);
final CountDownLatch cdl = new CountDownLatch(CONCURRENCY);
for (int i = 0; i < CONCURRENCY; i++) {
es.execute(new Runnable() {
@Override
public void run() {
try {
int size = 65000;
Date d = new Date();
long time = System.currentTimeMillis();
for (int i = 0; i < size; i++) {
String sd = ISODateFormatter.convertDateToString(d);
assert (sd != null);
}
total.addAndGet((System.currentTimeMillis() - time));
} catch (Throwable t) {
t.printStackTrace();
} finally {
cdl.countDown();
}
}
});
}
cdl.await();
es.shutdown();
LOG.info("TOTAL TIME:" + total.get());
LOG.info("AVERAGE TIME:" + (total.get() / CONCURRENCY));
}
}DateFormatter类：
public class ISODateFormatter {
private static final Logger LOG = Logger.getLogger(ISODateFormatter.class);
private static ThreadLocal<DateFormat> dfWithTZ = new ThreadLocal<DateFormat>() {
@Override
public DateFormat get() {
return super.get();
}
@Override
protected DateFormat initialValue() {
return new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ",
Locale.ENGLISH);
}
@Override
public void remove() {
super.remove();
}
@Override
public void set(DateFormat value) {
super.set(value);
}
};
public static String convertDateToString(Date date) {
if (date == null) {
return null;
}
try {
return dfWithTZ.get().format(date);
} catch (Exception e) {
LOG.error("!!! Error parsing dateString: " + date, e);
return null;
}
}
}有人建议去掉AtomicLong，所以只想分享一下，它并没有在增加平均时间方面起到任何作用：
##NOT USING ATOMIC LONG##
2014-02-28 11:03:52,790 [pool-1-thread-1] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:328
2014-02-28 11:03:52,868 [pool-1-thread-6] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:406
2014-02-28 11:03:52,821 [pool-1-thread-2] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:359
2014-02-28 11:03:52,821 [pool-1-thread-8] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:359
2014-02-28 11:03:52,868 [pool-1-thread-4] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:406
2014-02-28 11:03:52,915 [pool-1-thread-5] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:453
2014-02-28 11:03:52,930 [pool-1-thread-7] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:468
2014-02-28 11:03:52,930 [pool-1-thread-3] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:468
2014-02-28 11:03:52,930 [main] INFO net.ahm.graph.DateFormatterLoadTest - CONCURRENCY:8
##USING ATOMIC LONG##
2014-02-28 11:02:53,852 [main] INFO net.ahm.graph.DateFormatterLoadTest - TOTAL TIME:2726
2014-02-28 11:02:53,852 [main] INFO net.ahm.graph.DateFormatterLoadTest - CONCURRENCY:8
2014-02-28 11:02:53,852 [main] INFO net.ahm.graph.DateFormatterLoadTest - AVERAGE TIME:340
##NOT USING ATOMIC LONG##
2014-02-28 11:06:57,980 [pool-1-thread-3] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:312
2014-02-28 11:06:58,339 [pool-1-thread-8] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:671
2014-02-28 11:06:58,339 [pool-1-thread-4] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:671
2014-02-28 11:06:58,307 [pool-1-thread-7] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:639
2014-02-28 11:06:58,261 [pool-1-thread-6] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:593
2014-02-28 11:06:58,105 [pool-1-thread-15] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:437
2014-02-28 11:06:58,089 [pool-1-thread-13] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:421
2014-02-28 11:06:58,073 [pool-1-thread-1] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:405
2014-02-28 11:06:58,073 [pool-1-thread-12] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:405
2014-02-28 11:06:58,042 [pool-1-thread-14] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:374
2014-02-28 11:06:57,995 [pool-1-thread-2] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:327
2014-02-28 11:06:57,995 [pool-1-thread-16] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:327
2014-02-28 11:06:58,385 [pool-1-thread-10] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:717
2014-02-28 11:06:58,385 [pool-1-thread-11] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:717
2014-02-28 11:06:58,417 [pool-1-thread-9] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:749
2014-02-28 11:06:58,418 [pool-1-thread-5] INFO net.ahm.graph.DateFormatterLoadTest - THREAD TIME:750
2014-02-28 11:06:58,418 [main] INFO net.ahm.graph.DateFormatterLoadTest - CONCURRENCY:16
##USING ATOMIC LONG##
2014-02-28 11:07:57,510 [main] INFO net.ahm.graph.DateFormatterLoadTest - TOTAL TIME:9365
2014-02-28 11:07:57,510 [main] INFO net.ahm.graph.DateFormatterLoadTest - CONCURRENCY:16
2014-02-28 11:07:57,510 [main] INFO net.ahm.graph.DateFormatterLoadTest - AVERAGE TIME:585页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/22098904
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