Hello, I would like to read two files in two different threads. I have made a first version reading the first then the second and it takes 2.8s (native). I decided to make a threaded version and before any use of thread I realized that just linking no even using it to the threads library makes my first version of the program to run in 12s ! I use pcre, extlib, csv libraries as well. I guess it might come from GC slowing down thinks here, doesn't it ? Where can it come from otherwise ? Is there a workaround or something I should know ? Can ocaml use multiple cores ? Do you have few pointers on libraries to make parallel I/Os ? Thanks, RĂ©mi