Re: [PATCH 3/3] mm: adjust rss counters for migration entiries

[Konstantin Khlebnikov <khlebnikov@openvz.org>]

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This bug can be easily triggered by test-tool in attachment.
I run it with with this arguments: ./mm-thp-torture 100 100

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/*
 * torture-test for transparent huge pages,
 * memory migration and memory compaction =)
 *
 * usage: ./mm-thp-tortire <threads> <pages>
 *
 * to eat all avaliable huge pages:
 * threads * pages >= ram[mb] / 2[mb]
 *
 */

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <sys/mman.h>


#define PAGE_SIZE (4096)
#define HPAGE_SIZE (4096*512)

int main(int argc, char **argv)
{
	long pages, threads;
	char *buf, *ptr;

	if (argc < 3)
		return 2;

	signal(SIGCHLD, SIG_IGN);

	threads = atol(argv[1]);
	pages = atol(argv[2]);

	buf = mmap(NULL, (pages + 1) * HPAGE_SIZE, PROT_READ|PROT_WRITE,
			MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0);
	if (buf == MAP_FAILED)
		return 3;

	buf += HPAGE_SIZE - ((long)buf & (HPAGE_SIZE-1));

	while (--threads > 0 && !fork());

	while (1) {
		for ( ptr = buf ; ptr < buf + pages * HPAGE_SIZE ;
				ptr += HPAGE_SIZE ) {
			if (mmap(ptr, HPAGE_SIZE, PROT_READ|PROT_WRITE,
			    MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE|MAP_FIXED,
			    -1, 0) != ptr)
				return 4;
			*ptr = 0;
			munmap(ptr + PAGE_SIZE, HPAGE_SIZE - PAGE_SIZE);
		}
		if (!fork())
			exit(0);
		munmap(buf, pages * HPAGE_SIZE);
	}
	return 0;
}