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From: Kefeng Wang <wangkefeng.wang@huawei.com>
To: <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
        zhongjiang <zhongjiang@huawei.com>, Qiuxishi <qiuxishi@huawei.com>,
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Subject: [Question] Mlocked count will not be decreased
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Date: Tue, 23 May 2017 22:41:34 +0800
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Hi All,

Mlocked in meminfo will be increasing with an small testcase, and never be released in mainline,
here is a testcase[1] to reproduce the issue, but the centos7.2/7.3 will not increase.

Is it normal?

Thanks,
Kefeng




[1] testcase
linux:~ # cat test_mlockall.sh
grep Mlocked /proc/meminfo
 for j in `seq 0 10`
 do
	for i in `seq 4 15`
	do
		./p_mlockall >> log &
	done
	sleep 0.2
done
grep Mlocked /proc/meminfo


linux:~ # cat p_mlockall.c
#include <sys/mman.h>
#include <stdlib.h>
#include <stdio.h>

#define SPACE_LEN	4096

int main(int argc, char ** argv)
{
	int ret;
	void *adr = malloc(SPACE_LEN);
	if (!adr)
		return -1;
	
	ret = mlockall(MCL_CURRENT | MCL_FUTURE);
	printf("mlcokall ret = %d\n", ret);

	ret = munlockall();
	printf("munlcokall ret = %d\n", ret);

	free(adr);
	return 0;
}