Hi all, While trying to compile my multithreaded app written for Linux on Cygwin to run on Windows, I discovered the app would perform 8x slower on a machine with the same specs. I then went on to triage the issue and found that if I set CPU affinity of that process to 1 (i.e. single core), I'd get it to speed up to almost the speed I'd get under Linux (set to single core too).
I dug deeper and had my suspicion on a Cygwin bug. I suspected a problem in its thread singalling (condvar). So to test my hypothesis, I created a minimal test case to show case this issue. This minimal test case compiled on MSVC++ too and the difference is staggering. What you'll find is if you started the process with CPU Aff = 1, you'll get it to run >8x as fast as the default. On my machine, it took 4300ms to run in dual core mode, 460ms to run when CPU Aff = 1. Setup: Cygwin WinXP SP3 2GB RAM Core2Duo 2.33GHz All firewalls disabled Virus / Malware scanners disabled Boost 1.48.0 (as per official Cygwin installation) [Only for test case app] Boost.Threadpool - http://threadpool.sourceforge.net Code to replicate the issue (get Boost.Threadpool from above): #include <boost/threadpool.hpp> #include <iostream> #include <time.h> inline int GetTickCount() { timespec t; clock_gettime(CLOCK_MONOTONIC, &t); return (((int)t.tv_sec) * 1000) + (t.tv_nsec / 1000000); } class Test { public: void Add() { } void Delete() { } }; int main(int argc, char** argv) { int start; { boost::threadpool::pool tp(50); Test test; start = GetTickCount(); for (int i=0; i<100000; i++) { tp.schedule(boost::bind(&Test::Add, &test)); tp.schedule(boost::bind(&Test::Delete, &test)); } tp.wait(); } int elapsed = GetTickCount() - start; std::cout << elapsed << std::endl; std::cin.get(); return 0; } Cheers, Zach -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
