Re: [LAD] Pipes vs. Message Queues

David Robillard: On my computer, sockets are sometimes slower than both pipes and queues. However, by making sure the two processes doesn't change CPU during runtime, sockets are always the fastest, and I get consistent results: Realtime, same CPU: [kjetil@ttleon c]$ ./ipc 4096 2000000 Sending a 4096 byte message 2000000 times. Pipe send time: 7.762312 Pipe recv time: 7.762423 Socket send time: 4.607025 Socket recv time: 4.607103 Queue send time: 7.278029 Queue recv time: 7.278052 Realtime, different CPUs: [kjetil@ttleon c]$ ./ipc 4096 2000000 Sending a 4096 byte message 2000000 times. Pipe recv time: 5.520099 Pipe send time: 5.519875 Socket send time: 2.856027 Socket recv time: 2.856136 Queue recv time: 3.049226 Queue send time: 3.049159 Non-realtime, same CPU: [kjetil@ttleon c]$ ./ipc 4096 2000000 Sending a 4096 byte message 2000000 times. Pipe send time: 7.331822 Pipe recv time: 7.332272 Socket send time: 4.520883 Socket recv time: 4.520959 Queue send time: 7.103408 Queue recv time: 7.103448 Non-realtime, different CPUs: [kjetil@ttleon c]$ ./ipc 4096 2000000 Sending a 4096 byte message 2000000 times. Pipe recv time: 4.305804 Pipe send time: 4.305587 Socket send time: 2.899696 Socket recv time: 2.899806 Queue recv time: 3.028210 Queue send time: 3.028151 [kjetil@ttleon c]$ diff -u ipc.c~ ipc.c --- ipc.c~ 2011-11-26 00:55:38.000000000 +0100 +++ ipc.c 2011-11-26 14:51:44.003407960 +0100 @@ -41,9 +41,10 @@ // Comment out this line to disable RT scheduling //#define SET_RT_SCHED 1 -#ifdef SET_RT_SCHED +#define _GNU_SOURCE +#define __USE_GNU #include <sched.h> -#endif +#include <pthread.h> static inline double elapsed_s(const struct timespec* start, const struct timespec* end) @@ -177,6 +178,14 @@ return time; } +static void bound_thread_to_cpu(int cpu){ + cpu_set_t set; + CPU_ZERO(&set); + CPU_SET(cpu,&set); + pthread_setaffinity_np(pthread_self(), sizeof(cpu_set_t), &set); +} + int main(int argc, char** argv) { @@ -218,6 +227,11 @@ return 1; } + if (child_pid ==0) + bound_thread_to_cpu(0); + else + bound_thread_to_cpu(1); // set to 0 to run both on the same CPU + #ifdef SET_RT_SCHED struct sched_param param; param.sched_priority = 90;