我有一个以 819.2 Hz (~1.2ms) 的速率向我的 QNX Neutrino 机器发送 UDP 数据包的源。我希望以尽可能少的延迟和抖动接收和处理这些消息。
我的第一个代码基本上是：
SetupUDPSocket();
while (true) {
recv(socket, buffer, BufferSize, MSG_WAITALL); // blocks until whole packet is received
processPacket(buffer);
}
问题是 recv() 仅在系统的每个计时器滴答时检查是否有新的数据包可用。计时器滴答声通常为 1ms。所以，如果我使用它，我会得到很大的抖动，因为我每 1 毫秒或每 2 毫秒处理一个数据包。我可以重置计时器刻度的大小，但这会影响整个系统（以及其他进程的其他计时器等）。而且我仍然会有抖动，因为我肯定不会完全匹配 819.2 Hz。
于是，我尝试使用网卡的中断线（5）。但似乎还有其他因素导致中断上升。我曾经遵循以下代码：
ThreadCtl(_NTO_TCTL_IO, 0);
SIGEV_INTR_INIT(&event);
iID = InterruptAttachEvent(IRQ5, &event, _NTO_INTR_FLAGS_TRK_MSK);
while(true) {
if (InterruptWait(0, NULL) == -1) {
std::cerr << "errno: " << errno << std::endl;
}
length = recv(socket, buffer, bufferSize, 0); // non-blocking this time
LogTimeAndLength();
InterruptUnmask(IRQ5, iID;
}
这会导致在开始时进行一次成功读取，然后在经过 0 次后读取 0 字节长度。看来，在执行 InterruptUnmask() 之后，InterruptWait() 根本不等待，所以必须已经有一个新的中断（或相同的？！）。
是否可以用网卡的中断线做类似的事情？是否还有其他可能以 819.2 Hz 的速率接收数据包？
关于网卡的一些信息：'pci -vvv' 输出：
Class = Network (Ethernet)
Vendor ID = 8086h, Intel Corporation
Device ID = 107ch, 82541PI Gigabit Ethernet Controller
PCI index = 0h
Class Codes = 020000h
Revision ID = 5h
Bus number = 4
Device number = 15
Function num = 0
Status Reg = 230h
Command Reg = 17h
I/O space access enabled
Memory space access enabled
Bus Master enabled
Special Cycle operations ignored
Memory Write and Invalidate enabled
Palette Snooping disabled
Parity Error Response disabled
Data/Address stepping disabled
SERR# driver disabled
Fast back-to-back transactions to different agents disabled
Header type = 0h Single-function
BIST = 0h Build-in-self-test not supported
Latency Timer = 40h
Cache Line Size= 8h un-cacheable
PCI Mem Address = febc0000h 32bit length 131072 enabled
PCI Mem Address = feba0000h 32bit length 131072 enabled
PCI IO Address = ec00h length 64 enabled
Subsystem Vendor ID = 8086h
Subsystem ID = 1376h
PCI Expansion ROM = feb80000h length 131072 disabled
Max Lat = 0ns
Min Gnt = 255ns
PCI Int Pin = INT A
Interrupt line = 5
CPU Interrupt = 5h
Capabilities Pointer = dch
Capability ID = 1h - Power Management
Capabilities = c822h - 28002000h
Capability ID = 7h - PCI-X
Capabilities = 2h - 400000h
Device Dependent Registers:
0x040: 0000 0000 0000 0000 0000 0000 0000 0000
...
0x0d0: 0000 0000 0000 0000 0000 0000 01e4 22c8
0x0e0: 0020 0028 0700 0200 0000 4000 0000 0000
0x0f0: 0500 8000 0000 0000 0000 0000 0000 0000
和“nicinfo”输出：
wm1:
INTEL 82544 Gigabit (Copper) Ethernet Controller
Physical Node ID ........................... 000E0C C5F6DD
Current Physical Node ID ................... 000E0C C5F6DD
Current Operation Rate ..................... 100.00 Mb/s full-duplex
Active Interface Type ...................... MII
Active PHY address ....................... 0
Maximum Transmittable data Unit ............ 1500
Maximum Receivable data Unit ............... 0
Hardware Interrupt ......................... 0x5
Memory Aperture ............................ 0xfebc0000 - 0xfebdffff
Promiscuous Mode ........................... Off
Multicast Support .......................... Enabled
谢谢阅读！