On 19 Apr 2024, at 14:00, Andrew Warkentin <andreww...@gmail.com> wrote:
>
> Somehow I said Send()/Recv()/Reply() when I meant Call()/Recv()/Send()
> (MCS of course doesn't even have a distinct Reply() function).
the correct syscall to use is ReplyWait():
Recv(…);
while (1) {
ReplyWait(…);
}
Es per my blog: Send() and Recv() should only ever be used in initialisation
and exception handling.
> The QNX/Linux equivalent is:
>
> int main()
> {
> char buf[100];
> int f = open("/dev/null", O_WRONLY);
> int i;
> for (i = 0; i < 10; i++) {
> uint64_t start = __rdtsc();
> uint64_t end;
> int j;
> for (j = 0; j < 10000; j++){
> if (write(f, buf, 100) != 100){
> printf("cannot write\n");
> exit(1);
> }
> }
> end = __rdtsc();
> printf("cycles: %u\n", end - start);
> }
> }
so you’re using standard I/O to /dev/null
My Posix is a bit rusty, but this should be buffered in the library (i.e. most
calls will *not* result in a system call).
And, given that the output goes to /dev/null, the data may be thrown away
completely.
Basically you’re measuring the cost of a function call.
Gernot
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