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recv() is Missing from Results

Alon_Tal
Beginner
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[cpp]The following snippet produces results which I think might be faulty. After profiling, I am not seeing any calls to recv(), neither using sampling nor using call-graph runs.

I run this tester and stream UDP traffic to it, and wait until it exits (After 20000 packets).
The results attribute the highest "self time" to cout related operations (put(), operator<<), which is unlikely, as they only get called 24 times, whereas recv() gets called thousands of times, and should be quite expensive.

My question: How can I see how much time was spent in recv()?



#include #include #include using std::cerr; using std::cout; using std::endl; int main() { int sock = -1; int retval = 0; sock = socket(AF_INET, SOCK_DGRAM, 0); if (sock == -1) { cerr << "Failed to allocate socket. Error " << sock << " (" << strerror(errno) << ")" << endl; return 1; } sockaddr_in addr; memset(&addr, 0, sizeof(addr)); addr.sin_family = AF_INET; addr.sin_port = htons(51258); addr.sin_addr.s_addr = INADDR_ANY; socklen_t socklen = sizeof(addr); retval = bind(sock, (const sockaddr*)&addr, socklen); if (retval == -1) { cerr << "Failed to bind socket. Error " << sock << " (" << strerror(errno) << ")" << endl; return 1; } cout << "Calling recv()..." << endl; char buf[1024] = {0}; int i = 0; while (1) { retval = recv(sock, buf, sizeof(buf), 0); if (retval == -1) { cerr << "Failed to recv. Error " << sock << " (" << strerror(errno) << ")" << endl; return 1; } if (i++ % 1000 == 0) { cout << "Received " << retval << " bytes" << endl; if (i > 20000) { cout << "Stopping" << endl; break; } } } [/cpp]
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David_A_Intel1
Employee
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Sampling will not catch it unless significant time is spent in the recv() routine and call graph won't record it if it is ring0 code. Is recv() a kernel call. Also, are you sure it is not inlined by the compiler? Are you building with optimizations on or off?
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