[BUG]getShort等类型，每次都会spin一次，cpu飙升

[wongjjjyi-create]

问题描述

com.alibaba.fastjson2.introspect.PropertyAccessorFactoryLambda#getByte的getInt(method) 这个调用被写在了 lambda 的方法体内部。而 getInt(method) 本身就是"会 spin 一个新 lambda"的操作(它内部调 LambdaMetafactory.metafactory 造 int 取值器)。

导致序列化一百万次 flag → getInt 被调 100 万次 → spin 100 万次 → $$Lambda$ 编号飙到 150 万

环境信息

• OS信息： Linux host-11-18-140-48 3.10.0-693.5.2.el7.jd_3313.x86_64 修复Readme的Codeconv配置 #1 SMP Wed May 2 14:35:41 CST 2018 x86_64 x86_64 x86_64 GNU/Linux
• JDK信息： Openjdk 1.8.0_312
• 版本信息：fastjson2 4.0.0

重现步骤

不断调用 ComplexPoJo2 sample = getIPBeanParentPOJO(new ComplexPoJo(), strlength);
logger.info("bigInfo payload: {}", LogUtils.dump(sample));进行日志打印，
其中getIPBeanParentPOJO为
@OverRide
public ComplexPoJo2 getIPBeanParentPOJO(ComplexPoJo beanParent,int length) throws InterruptedException {

    ThreadLocalRandom r = ThreadLocalRandom.current();
    ComplexPoJo2.Status[] statuses = ComplexPoJo2.Status.values();

    ComplexPoJo2 resp = new ComplexPoJo2();

    // 基本类型
    resp.setId(r.nextInt(1, 100000));
    resp.setTimestamp(System.currentTimeMillis() - r.nextLong(0, 86400_000L));
    resp.setScore(r.nextDouble(0.0, 100.0));
    resp.setActive(r.nextBoolean());
    resp.setLevel((short) r.nextInt(1, 10));
    resp.setFlag((byte) r.nextInt(0, 128));

    // 字符串
    resp.setName("user-" + getRandomStringFast(8));
    resp.setDescription(getRandomStringFast(length));

    // 日期
    resp.setCreateTime(new Date(System.currentTimeMillis() - r.nextLong(0, 30L * 86400_000)));
    resp.setUpdateTime(beanParent.getCreateTime() != null ? beanParent.getCreateTime() : new Date());

    // BigDecimal
    resp.setAmount(BigDecimal.valueOf(r.nextDouble(1.0, 9999.99)).setScale(2, BigDecimal.ROUND_HALF_UP));

    // 枚举
    resp.setStatus(statuses[r.nextInt(statuses.length)]);

    // 数组
    byte[] bin = new byte[r.nextInt(16, 64)];
    r.nextBytes(bin);
    resp.setBinaryData(bin);
    int[] intArr = new int[r.nextInt(4, 12)];
    for (int i = 0; i < intArr.length; i++) intArr[i] = r.nextInt(0, 1000);
    resp.setIntArray(intArr);

    // List<String> tags
    int tagCount = r.nextInt(2, 6);
    List<String> tags = new ArrayList<>(tagCount);
    for (int i = 0; i < tagCount; i++) tags.add("tag-" + getRandomStringFast(4));
    resp.setTags(tags);

    // List<Integer> scores
    int scoreCount = r.nextInt(3, 8);
    List<Integer> scores = new ArrayList<>(scoreCount);
    for (int i = 0; i < scoreCount; i++) scores.add(r.nextInt(0, 100));
    resp.setScores(scores);

    // Set<String> categories
    int catCount = r.nextInt(2, 5);
    Set<String> categories = new HashSet<>(catCount);
    for (int i = 0; i < catCount; i++) categories.add("cat-" + getRandomStringFast(3));
    resp.setCategories(categories);

    // Map<String, String> attributes
    int attrCount = r.nextInt(2, 5);
    Map<String, String> attrs = new HashMap<>(attrCount);
    for (int i = 0; i < attrCount; i++) attrs.put("attr-" + i, getRandomStringFast(8));
    resp.setAttributes(attrs);

    // Map<String, Integer> counters
    int counterCount = r.nextInt(2, 5);
    Map<String, Integer> counters = new HashMap<>(counterCount);
    for (int i = 0; i < counterCount; i++) counters.put("counter-" + i, r.nextInt(0, 10000));
    resp.setCounters(counters);

    // Map<String, MetaEntry>
    int metaCount = r.nextInt(2, 4);
    Map<String, ComplexPoJo2.MetaEntry> metaMap = new HashMap<>(metaCount);
    for (int i = 0; i < metaCount; i++) {
        ComplexPoJo2.MetaEntry entry = new ComplexPoJo2.MetaEntry();
        entry.setKey("mk-" + i);
        entry.setValue(getRandomStringFast(12));
        entry.setCount(r.nextInt(1, 100));
        Map<String, String> extra = new HashMap<>(2);
        extra.put("ex1", getRandomStringFast(6));
        extra.put("ex2", getRandomStringFast(6));
        entry.setExtra(extra);
        metaMap.put("meta-" + i, entry);
    }
    resp.setMetaMap(metaMap);

    // 嵌套对象 AddressInfo
    resp.setAddress(randomAddress(r));

    // List<OrderItem>
    int itemCount = r.nextInt(2, 5);
    List<ComplexPoJo2.OrderItem> items = new ArrayList<>(itemCount);
    for (int i = 0; i < itemCount; i++) items.add(randomOrderItem(r));
    resp.setItems(items);

    // Map<String, List<OrderItem>>
    int groupCount = r.nextInt(2, 4);
    Map<String, List<ComplexPoJo2.OrderItem>> grouped = new HashMap<>(groupCount);
    for (int i = 0; i < groupCount; i++) {
        int gItemCount = r.nextInt(1, 4);
        List<ComplexPoJo2.OrderItem> gItems = new ArrayList<>(gItemCount);
        for (int j = 0; j < gItemCount; j++) gItems.add(randomOrderItem(r));
        grouped.put("group-" + i, gItems);
    }
    resp.setGroupedItems(grouped);

    return resp;
}

private ComplexPoJo2.AddressInfo randomAddress(ThreadLocalRandom r) {
    String[] cities = {"Beijing", "Shanghai", "Guangzhou", "Shenzhen", "Hangzhou", "Chengdu", "Wuhan"};
    ComplexPoJo2.AddressInfo addr = new ComplexPoJo2.AddressInfo();
    addr.setCountry("China");
    addr.setProvince("Province-" + getRandomStringFast(4));
    addr.setCity(cities[r.nextInt(cities.length)]);
    addr.setStreet("Street-" + r.nextInt(1, 999));
    addr.setZipCode(String.format("%06d", r.nextInt(100000, 999999)));
    addr.setLatitude(r.nextDouble(18.0, 53.0));
    addr.setLongitude(r.nextDouble(73.0, 135.0));
    return addr;
}

private ComplexPoJo2.OrderItem randomOrderItem(ThreadLocalRandom r) {
    ComplexPoJo2.OrderItem item = new ComplexPoJo2.OrderItem();
    item.setItemId("item-" + getRandomStringFast(6));
    item.setItemName("Product-" + getRandomStringFast(8));
    item.setQuantity(r.nextInt(1, 50));
    double unitPrice = r.nextDouble(1.0, 999.99);
    item.setUnitPrice(unitPrice);
    item.setTotalPrice(BigDecimal.valueOf(unitPrice * item.getQuantity()).setScale(2, BigDecimal.ROUND_HALF_UP));
    Map<String, String> props = new HashMap<>(3);
    props.put("color", getRandomStringFast(5));
    props.put("size", getRandomStringFast(3));
    props.put("brand", getRandomStringFast(6));
    item.setProperties(props);
    item.setDeliveryAddress(randomAddress(r));
    return item;
}

public static String getRandomStringFast(int length){
    final String pool="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    ThreadLocalRandom random=ThreadLocalRandom.current();
    char[] buf=new char[length];
    for(int i=0;i<length;i++){
        buf[i]=pool.charAt(random.nextInt(62));
    }
    return new String(buf);
}

期待的正确结果

压测后，性能不差于fastjson1.x

fastjson1和fastjson2火焰图

218363_20260710182318667.html
218368_20260710185516618.html

[scmod]

看代码每个类只在创建readerwriter时候每个字段生成一个,跟调用次数没有关系吧?

[wongjjjyi-create]

您好，这个是ai分析的结果，

火焰图定量差异（占 B 总时长的百分比）

栈帧	B%	A%	说明
LambdaMetafactory.metafactory	23.79%	0	fastjson2 每次为 getter 生成 lambda
InnerClassLambdaMetafactory.buildCallSite	23.29%	0	同上
InnerClassLambdaMetafactory.spinInnerClass	19.92%	0	ASM 生成匿名类字节码
Unsafe.defineAnonymousClass / Unsafe_DefineAnonymousClass	18.24% / 16.09%	0	JVM 定义匿名类
SystemDictionary::parse_stream / ClassFileParser::parseClassFile	15.92% / 11.68%	0	解析类字节码
PropertyAccessorFactoryLambda.getInt/getByte/getShort	24.83% / 13.58% / 12.52%	0	上面这堆的调用入口
[deoptimization]	7.73%	0	JIT 反优化（生成新类导致）
FieldWriterInt8Value.write / FieldWriterInt16Value.write	13.69% / 12.55%	0	byte/short 字段写入路径

定位到的可疑代码

core/src/main/java/com/alibaba/fastjson2/introspect/PropertyAccessorFactoryLambda.java:408-441：

public ToByteFunction<Object> getByte(Method method) {
    if (method == null) return null;
    return o -> (byte) getInt(method).applyAsInt(o);   // 每次调用都重新 getInt(method)!
}
public ToShortFunction<Object> getShort(Method method) { ... getInt(method) ... }
public ToCharFunction<Object>  getChar (Method method) { ... getInt(method) ... }

而 getInt(method) 内部（第 450 行起）每次都会调 LambdaMetafactory.metafactory(...) 新生成一个匿名类。

也就是说：

• 对每个 byte 属性的 getter，每次读值都会走一遍 LambdaMetafactory → spinInnerClass → Unsafe.defineAnonymousClass → 解析字节码 → 定义 class，顺带触发 JIT 反优化。
• getShort / getChar 同理。

对照 setByte/setShort/setChar（第 517–536 行）也是同一个 bug 模式：每次访问都调 setInt(method) 现造 lambda。

为什么 A（fastjson 1.x）反而快

fastjson 1.x 用 JavaBeanSerializer + 反射 MethodAccessor（GeneratedMethodAccessor139.invoke 25%），路径稳定，没有运行时 spin class，不触发 deopt。

修复建议

在 PropertyAccessorFactoryLambda.getByte/getShort/getChar 和 setByte/setShort/setChar 里，把 getInt(method) / setInt(method) 的结果 提出到 lambda 外层，只生成一次：

public ToByteFunction<Object> getByte(Method method) {
    if (method == null) return null;
    ToIntFunction<Object> fn = getInt(method);   // 只 spin 一次
    return o -> (byte) fn.applyAsInt(o);
}

对 getShort / getChar / setByte / setShort / setChar 做同样的提升。这块修完预期能干掉 B 中约 40% 左右的 CPU（所有 LambdaMetafactory / spinInnerClass / defineAnonymousClass / parseClassFile / deoptimization 相关帧）。

[wongjjjyi-create]

jdk17上此问题就没有了，jdk8上cpu消耗差距达到10%，代码一模一样，只有fastjson不同