Re: Efficient IPC mechanism on Linux

[Jamie Lokier]

Pavel Machek wrote:
> Can you make it available so we can test on, say, 900MHz athlon? Or
> you can have it tested on 1800MHz athlon64, that's about as high end
> as it can get.

I just deleted the program, so here's a rewrite :)

	#include <sys/mman.h>

	int main()
	{
		int i, j;
		for (j = 0; j < 64; j++) {
			volatile char * ptr =
				mmap (0, 4096 * 4096, PROT_READ | PROT_WRITE,
				      MAP_PRIVATE | MAP_ANON, -1, 0);
			for (i = 0; i < 4096; i++) {
	#if 1
				*(ptr + 4096 * i) = 0; /* Write */
	#else
				(void) *(ptr + 4096 * i); /* Read */
	#endif
			}
			munmap ((void *) ptr, 4096 * 4096);
		}
		return 0;
	}

Smallest results, from "gcc -o test test.c -O2; time ./test" on a
1500MHz dual Athlon 1800 MP:

Write:
	real	0m1.316s
	user	0m0.059s
	sys	0m1.256s

	==> 7531 cycles per page

Read:
	real	0m0.199s
	user	0m0.053s
	sys	0m0.146s

	==> 1139 cycles per page

As I said, it's a crude upper bound.

-- Jamie
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