linux-kernel - [Question] Mlocked count will not be decreased

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Date:   Tue, 23 May 2017 22:41:34 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        zhongjiang <zhongjiang@...wei.com>,
        Qiuxishi <qiuxishi@...wei.com>,
        Yisheng Xie <xieyisheng1@...wei.com>,
        <wangkefeng.wang@...wei.com>
Subject: [Question] Mlocked count will not be decreased

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;
}