插入USB热点后，简单的Java程序慢了100倍 [英] Simple Java program 100 times slower after plugging in USB hotspot
问题描述
我有以下Java程序：
I have following Java program:
class Main {
public static void main(String[] args) throws java.io.IOException {
long start = System.nanoTime();
java.io.File.createTempFile("java_test", ".txt").delete();
System.out.println((System.nanoTime() - start ) / 1e9);
}
}
通常，执行需要大约63毫秒： / p>
Normally, it takes bout 63 miliseconds to execute:
$ java Main
0.06308555
但是，一旦我将Android手机作为USB热点连接，它需要更长的时间。取决于机器在3到40秒之间的任何地方：
But, once I connect Android phone as USB hotspot, it takes significantly longer. Depending on the machine anywhere from 3 to 40 seconds:
$ java Main
4.263285528
奇怪的是，这里没有任何东西实际通过网络传输 - 插入的网络适配器无关紧要。
The strange thing is that nothing here is actually transferred over the network - plugged network adapters shouldn't matter.
我做了一个回溯，看起来大部分时间花在了 NetworkInterface.getAll 方法：
I did a backtrace and it looks like majority of time is spent in NetworkInterface.getAll method:
"main" #1 prio=5 os_prio=0 tid=0x00000000023ae000 nid=0x142c runnable [0x000000000268d000]
java.lang.Thread.State: RUNNABLE
at java.net.NetworkInterface.getAll(Native Method)
at java.net.NetworkInterface.getNetworkInterfaces(Unknown Source)
at sun.security.provider.SeedGenerator.addNetworkAdapterInfo(Unknown Source)
at sun.security.provider.SeedGenerator.access$000(Unknown Source)
at sun.security.provider.SeedGenerator$1.run(Unknown Source)
at sun.security.provider.SeedGenerator$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.security.provider.SeedGenerator.getSystemEntropy(Unknown Source)
at sun.security.provider.SecureRandom$SeederHolder.<clinit>(Unknown Source)
at sun.security.provider.SecureRandom.engineNextBytes(Unknown Source)
- locked <0x000000076afa2820> (a sun.security.provider.SecureRandom)
at java.security.SecureRandom.nextBytes(Unknown Source)
- locked <0x000000076af6bdc8> (a java.security.SecureRandom)
at java.security.SecureRandom.next(Unknown Source)
at java.util.Random.nextLong(Unknown Source)
at java.io.File$TempDirectory.generateFile(Unknown Source)
at java.io.File.createTempFile(Unknown Source)
at java.io.File.createTempFile(Unknown Source)
at Main.main(Main.java:4)
反过来，大部分时间似乎花费在 GetIfTable Windows API方法：
which, in turn, seems to spend most of the time in GetIfTable Windows API method:
Child-SP RetAddr Call Site
00000000`0257ed78 000007fe`fd7210ba ntdll!NtDeviceIoControlFile+0xa
00000000`0257ed80 000007fe`fd721252 nsi+0x10ba
00000000`0257ee20 000007fe`fd7211f9 nsi!NsiEnumerateObjectsAllParametersEx+0x2e
00000000`0257ee60 000007fe`fd7217b0 nsi!NsiEnumerateObjectsAllParameters+0xc9
00000000`0257ef00 000007fe`f9c7928d nsi!NsiAllocateAndGetTable+0x184
00000000`0257efd0 00000000`6f8c5a01 IPHLPAPI!GetIfTable+0xa9
00000000`0257f090 00000000`6f8c6980 net!Java_java_net_NetworkInterface_getMTU0+0x1a1
00000000`0257f150 00000000`6f8c6e57 net!Java_java_net_NetworkInterface_isP2P0_XP+0x88
00000000`0257f270 00000000`6f8c6058 net!Java_java_net_NetworkInterface_getAll_XP+0x23
00000000`0257f2a0 00000000`02867f54 net!Java_java_net_NetworkInterface_getAll+0x2c
GetIfTable 似乎是有问题的功能。我在示例程序中观察到同样的减速： https://msdn.microsoft.com/en-us/library/windows/desktop/aa365943(v = vs.85）.aspx 以及以下代码段：
GetIfTable seems to be the problematic function. I'm observing the same slowdown both in example program from: https://msdn.microsoft.com/en-us/library/windows/desktop/aa365943(v=vs.85).aspx and with following snippet:
#include <iphlpapi.h>
#include <stdlib.h>
int main() {
DWORD dwSize = sizeof(MIB_IFTABLE);
MIB_IFTABLE *pIfTable = malloc(dwSize);
GetIfTable(pIfTable, &dwSize, FALSE);
pIfTable = malloc(dwSize);
GetIfTable(pIfTable, &dwSize, FALSE);
return 0;
}
如何修复或解决此问题？
我可以自己创建临时文件，避免调用NetworkInterface.getNetworkInterfaces，但SecureRandom遍布Java标准库。
有没有办法强制SecureRandom不使用GetIfTable？
How do I fix or workaround this problem? I can create temporary files on my own and avoid calling NetworkInterface.getNetworkInterfaces but SecureRandom is used all over Java standard library. Is there a way to force SecureRandom not to use GetIfTable?
Java版本：
> java -version
java version "1.8.0_101"
Java(TM) SE Runtime Environment (build 1.8.0_101-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.101-b13, mixed mode)
Windows版本：
Windows version:
OS Name: Microsoft Windows 7 Professional
OS Version: 6.1.7601 Service Pack 1 Build 7601
有问题的网络适配器：
Name [00000020] Remote NDIS based Internet Sharing Device
Adapter Type Ethernet 802.3
Product Type Remote NDIS based Internet Sharing Device
Installed Yes
PNP Device ID USB\VID_0FCE&PID_71C4&MI_00\7&6BE3F3B&0&0000
Last Reset 8/14/2016 12:26 PM
Index 20
Service Name usb_rndisx
IP Address 192.168.42.183, fe80::90ab:3786:4396:2870
IP Subnet 255.255.255.0, 64
Default IP Gateway 192.168.42.129
DHCP Enabled Yes
DHCP Server 192.168.42.129
DHCP Lease Expires 8/14/2016 3:27 PM
DHCP Lease Obtained 8/14/2016 2:27 PM
MAC Address 02:18:61:77:7D:72
Driver c:\windows\system32\drivers\usb8023x.sys (6.1.7600.16385, 19.50 KB (19,968 bytes), 7/14/2009 2:09 AM)
推荐答案
SecureRandom 的默认实现扫描网络接口作为系统熵的另一个来源。为了避免这种情况，您需要注册一个自定义的 java.security.Provider 包含 SecureRandomSpi 。
Default implementation of SecureRandom scans network interfaces as an additional source of system entropy. In order to avoid this, you need to register a custom java.security.Provider that contains a different implementation of SecureRandomSpi.
幸运的是，JDK for Windows已经有了合适的 SecureRandomSpi 依赖于Microsoft Crypto API的实现： sun.security.mscapi.PRNG 。虽然这是非公共API，但是所有版本的OpenJDK和Oracle JDK中都存在从1.6到9的类，并且无论如何都可以使用后备。
Fortunately, JDK for Windows already has a suitable SecureRandomSpi implementation that relies on Microsoft Crypto API: sun.security.mscapi.PRNG. Though this is non-public API, the class exists in all versions of OpenJDK and Oracle JDK from 1.6 to 9, and the fallback is available anyway.
有两种方法注册MS Crypto PRNG作为默认的SecureRandom算法。
There are two ways to register MS Crypto PRNG as the default SecureRandom algorithm.
1。从应用程序中调用 WindowsSecureRandom.register （）一开始。
1. From within the application by calling WindowsSecureRandom.register() at the very beginning.
import java.security.Provider;
import java.security.Security;
public class WindowsSecureRandom extends Provider {
private static final String MSCAPI = "sun.security.mscapi.PRNG";
private WindowsSecureRandom() {
super("WindowsSecureRandom Provider", 1.0, null);
putService(new Service(this, "SecureRandom", "Windows-PRNG", MSCAPI, null, null));
}
public static void register() {
if (System.getProperty("os.name").contains("Windows")) {
try {
Class.forName(MSCAPI);
Security.insertProviderAt(new WindowsSecureRandom(), 1);
} catch (ClassNotFoundException e) {
// Fallback to default implementation
}
}
}
}
2. 通过重新排序％JAVA_HOME％\ jre \ lib \\中的提供商列表\\ security\java.security file。
2. By reordering provider list in %JAVA_HOME%\jre\lib\security\java.security file.
security.provider.1=sun.security.mscapi.SunMSCAPI <<<--- make it the first provider
security.provider.2=sun.security.provider.Sun
security.provider.3=sun.security.rsa.SunRsaSign
security.provider.4=sun.security.ec.SunEC
security.provider.5=com.sun.net.ssl.internal.ssl.Provider
...
我已使用任何解决方案验证 SeedGenerator 和 NetworkInterface 不再加载类。
I've verified that with either solutions SeedGenerator and NetworkInterface classes are no longer loaded.
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