Hi,
v2 -> v3: modified variables' type, updated overcommit_memory_test function,
          updated the comment lines.
please review it again, any comments are welcome.

There are two tunables overcommit_memory and overcommit_ratio under
/proc/sys/vm/, which can control memory overcommitment.

The overcommit_memory tunable contains a flag that enables memory
overcommitment, it has three values:
- When this flag is 0, the kernel attempts to estimate the amount
  of free memory left when userspace requests more memory.
- When this flag is 1, the kernel pretends there is always enough
  memory until it actually runs out.
- When this flag is 2, the kernel uses a "never overcommit" policy
  that attempts to prevent any overcommit of memory.

The overcommit_ratio tunable defines the amount by which the kernel
overextends its memory resources in the event that overcommit_memory
is set to the value of 2. The value in this file represents a
percentage added to the amount of actual RAM in a system when
considering whether to grant a particular memory request.
The general formula for this tunable is:
CommitLimit = SwapTotal + MemTotal * overcommit_ratio
CommitLimit, SwapTotal and MemTotal can read from /proc/meminfo.

The program is designed to test the two tunables:

When overcommit_memory = 0, allocatable memory can't overextends
the amount of free memory. I choose the three cases:
a. less than free_total:    free_total / 2, alloc should pass.
b. equal to free_total:     free_total,     alloc should pass.
c. greater than free_total: free_total * 2, alloc should fail.

When overcommit_memory = 1, it can alloc enough much memory, I
choose the three cases:
a. less than sum_total:    sum_total / 2, alloc should pass.
b. equal to sum_total:     sum_total,     alloc should pass.
c. greater than sum_total: sum_total * 2, alloc should pass.
*note: sum_total = SwapTotal + MemTotal

When overcommit_memory = 2,
allocatable memory = CommitLimit - Committed_As
I define it as commit_left, also I choose three cases:
a. less than commit_left:    commit_left / 2, alloc should pass.
b. greater than commit_left: commit_left * 2, alloc should fail.
c. overcommit limit:         CommitLimit,     alloc should fail.
*note: CommitLimit is the current overcommit limit.
       Committed_AS is the amount of memory that system has used.
why I din't choose 'equal to commit_left' as a case, because in
this case, the result is not fixed after I tested some times.

References:
- Documentation/sysctl/vm.txt
- Documentation/vm/overcommit-accounting

Signed-off-by: Zhouping Liu <z...@redhat.com>
---
 runtest/mm                                       |    7 +
 testcases/kernel/mem/tunable/Makefile            |   42 ++++
 testcases/kernel/mem/tunable/overcommit_memory.c |  282 ++++++++++++++++++++++
 3 files changed, 331 insertions(+), 0 deletions(-)
 create mode 100644 testcases/kernel/mem/tunable/Makefile
 create mode 100644 testcases/kernel/mem/tunable/overcommit_memory.c

-- 
Thanks,
Zhouping Liu
From c27ff0aec57cf015856473cd22b835e06660b23d Mon Sep 17 00:00:00 2001
From: Zhouping Liu <z...@redhat.com>
Date: Tue, 30 Aug 2011 19:54:53 +0800
Subject: [PATCH 2/2] mem/tunable: new testcase of memory overcommit

There are two tunables overcommit_memory and overcommit_ratio under
/proc/sys/vm/, which can control memory overcommitment.

The overcommit_memory contains a flag that enables memory
overcommitment, it has three values:
- When this flag is 0, the kernel attempts to estimate the amount
  of free memory left when userspace requests more memory.
- When this flag is 1, the kernel pretends there is always enough
  memory until it actually runs out.
- When this flag is 2, the kernel uses a "never overcommit" policy
  that attempts to prevent any overcommit of memory.

The overcommit_ratio tunable defines the amount by which the kernel
overextends its memory resources in the event that overcommit_memory
is set to the value of 2. The value in this file represents a
percentage added to the amount of actual RAM in a system when
considering whether to grant a particular memory request.
The general formula for this tunable is:
CommitLimit = SwapTotal + MemTotal * overcommit_ratio
CommitLimit, SwapTotal and MemTotal can read from /proc/meminfo.

The program is designed to test the two tunables:

When overcommit_memory = 0, allocatable memory can't overextends
the amount of free memory. I choose the three cases:
a. less than free_total:    free_total / 2, alloc should pass.
b. equal to free_total:     free_total,     alloc should pass.
c. greater than free_total: free_total * 2, alloc should fail.

When overcommit_memory = 1, it can alloc enough much memory, I
choose the three cases:
a. less than sum_total:    sum_total / 2, alloc should pass.
b. equal to sum_total:     sum_total,     alloc should pass.
c. greater than sum_total: sum_total * 2, alloc should pass.
*note: sum_total = SwapTotal + MemTotal

When overcommit_memory = 2,
allocatable memory = CommitLimit - Committed_As
I define it as commit_left, also I choose three cases:
a. less than commit_left:    commit_left / 2, alloc should pass.
b. greater than commit_left: commit_left * 2, alloc should fail.
c. overcommit limit:         CommitLimit,     alloc should fail.
*note: CommitLimit is the current overcommit limit.
       Committed_AS is the amount of memory that system has used.
why I din't choose 'equal to commit_left' as a case, because in
this case, the result is not fixed after I tested some times.

References:
- Documentation/sysctl/vm.txt
- Documentation/vm/overcommit-accounting

Signed-off-by: Zhouping Liu <z...@redhat.com>
---
 runtest/mm                                       |    7 +
 testcases/kernel/mem/tunable/Makefile            |   42 ++++
 testcases/kernel/mem/tunable/overcommit_memory.c |  282 ++++++++++++++++++++++
 3 files changed, 331 insertions(+), 0 deletions(-)
 create mode 100644 testcases/kernel/mem/tunable/Makefile
 create mode 100644 testcases/kernel/mem/tunable/overcommit_memory.c

diff --git a/runtest/mm b/runtest/mm
index 615f1f1..fb71189 100644
--- a/runtest/mm
+++ b/runtest/mm
@@ -82,3 +82,10 @@ thp01 thp01 -I 120
 
 vma01 vma01
 vma02 vma02
+
+overcommit_memory overcommit_memory
+overcommit_memory_1 overcommit_memory -R 0
+overcommit_memory_2 overcommit_memory -R 30
+overcommit_memory_3 overcommit_memory -R 80
+overcommit_memory_4 overcommit_memory -R 100
+overcommit_memory_5 overcommit_memory -R 200
diff --git a/testcases/kernel/mem/tunable/Makefile b/testcases/kernel/mem/tunable/Makefile
new file mode 100644
index 0000000..8ab52da
--- /dev/null
+++ b/testcases/kernel/mem/tunable/Makefile
@@ -0,0 +1,42 @@
+#
+#  Copyright (C) 2011  Red Hat, Inc.
+#
+#  This program is free software;  you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation; either version 2 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY;  without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+#  the GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program;  if not, write to the Free Software
+#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+#
+
+top_srcdir              ?= ../../../..
+
+include $(top_srcdir)/include/mk/testcases.mk
+
+LDLIBS			+= $(NUMA_LIBS) -lmem
+LIBDIR			:= ../lib
+LIB			:= $(LIBDIR)/libmem.a
+FILTER_OUT_DIRS		:= $(LIBDIR)
+LDFLAGS			+= -L$(LIBDIR)
+
+$(LIBDIR):
+	mkdir -p "$@"
+
+$(LIB): $(LIBDIR)
+	$(MAKE) -C $^ -f "$(abs_srcdir)/$^/Makefile" all
+
+MAKE_DEPS		:= $(LIB)
+
+trunk-clean:: | lib-clean
+
+lib-clean:: $(LIBDIR)
+	$(MAKE) -C $^ -f "$(abs_srcdir)/$^/Makefile" clean
+
+include $(top_srcdir)/include/mk/generic_leaf_target.mk
diff --git a/testcases/kernel/mem/tunable/overcommit_memory.c b/testcases/kernel/mem/tunable/overcommit_memory.c
new file mode 100644
index 0000000..6c51d1c
--- /dev/null
+++ b/testcases/kernel/mem/tunable/overcommit_memory.c
@@ -0,0 +1,282 @@
+/*
+ * Description:
+ *
+ * There are two tunables overcommit_memory and overcommit_ratio under
+ * /proc/sys/vm/, which can control memory overcommitment.
+ *
+ * The overcommit_memory contains a flag that enables memory
+ * overcommitment, it has three values:
+ * - When this flag is 0, the kernel attempts to estimate the amount
+ *   of free memory left when userspace requests more memory.
+ * - When this flag is 1, the kernel pretends there is always enough
+ *   memory until it actually runs out.
+ * - When this flag is 2, the kernel uses a "never overcommit" policy
+ *   that attempts to prevent any overcommit of memory.
+ *
+ * The overcommit_ratio tunable defines the amount by which the kernel
+ * overextends its memory resources in the event that overcommit_memory
+ * is set to the value of 2. The value in this file represents a
+ * percentage added to the amount of actual RAM in a system when
+ * considering whether to grant a particular memory request.
+ * The general formula for this tunable is:
+ * CommitLimit = SwapTotal + MemTotal * overcommit_ratio
+ * CommitLimit, SwapTotal and MemTotal can read from /proc/meminfo.
+ *
+ * The program is designed to test the two tunables:
+ *
+ * When overcommit_memory = 0, allocatable memory can't overextends
+ * the amount of free memory. I choose the three cases:
+ * a. less than free_total:    free_total / 2, alloc should pass.
+ * b. equal to free_total:     free_total,     alloc should pass.
+ * c. greater than free_total: free_total * 2, alloc should fail.
+ *
+ * When overcommit_memory = 1, it can alloc enough much memory, I
+ * choose the three cases:
+ * a. less than sum_total:    sum_total / 2, alloc should pass
+ * b. equal to sum_total:     sum_total,     alloc should pass
+ * c. greater than sum_total: sum_total * 2, alloc should pass
+ * *note: sum_total = SwapTotal + MemTotal
+ *
+ * When overcommit_memory = 2,
+ * allocatable memory = CommitLimit - Committed_AS
+ * I define it as commit_left, also I choose three cases:
+ * a. less than commit_left:    commit_left / 2, alloc should pass
+ * b. greater than commit_left: commit_left * 2, alloc should fail
+ * c. overcommit limit:         CommitLimit,     alloc should fail
+ * *note: CommitLimit is the current overcommit limit.
+ *        Committed_AS is the amount of memory that system has used.
+ * why I din't choose 'equal to commit_left' as a case, because in
+ * this case, the result is not fixed after I tested some times.
+ *
+ * References:
+ * - Documentation/sysctl/vm.txt
+ * - Documentation/vm/overcommit-accounting
+ *
+ * ********************************************************************
+ * Copyright (C) 2011 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * Further, this software is distributed without any warranty that it
+ * is free of the rightful claim of any third person regarding
+ * infringement or the like.  Any license provided herein, whether
+ * implied or otherwise, applies only to this software file.  Patent
+ * licenses, if any, provided herein do not apply to combinations of
+ * this program with other software, or any other product whatsoever.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ * ********************************************************************
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <linux/mman.h>
+#include "test.h"
+#include "usctest.h"
+#include "../include/mem.h"
+
+#define FILE_OVER_MEM		PATH_SYSVM "overcommit_memory"
+#define FILE_OVER_RATIO		PATH_SYSVM "overcommit_ratio"
+#define DEFAULT_OVER_RATIO	50LL
+#define EXPECT_PASS		0
+#define EXPECT_FAIL		1
+
+char *TCID = "overcommit_memory";
+static long long old_overcommit_memory;
+static long long old_overcommit_ratio;
+static long long overcommit_ratio;
+static long long sum_total;
+static long long free_total;
+static long long commit_limit;
+static long long commit_left;
+static int R_flag;
+static char *R_opt;
+option_t options[] = {
+	{ "R:", &R_flag, &R_opt },
+	{ NULL, NULL, NULL }
+};
+
+
+static void overcommit_memory_test(void);
+static int heavy_malloc(long long size);
+static void alloc_and_check(long long size, int expect_result);
+static void usage(void);
+static void update_mem(void);
+
+int main(int argc, char *argv[])
+{
+	char *msg;
+	int lc;
+
+	overcommit_ratio = DEFAULT_OVER_RATIO;
+
+	msg = parse_opts(argc, argv, options, &usage);
+	if (msg != NULL) {
+		tst_brkm(TBROK, NULL, "OPTION PARSING ERROR - %s", msg);
+		tst_exit();
+	}
+
+	if (R_flag) {
+		overcommit_ratio = atoll(R_opt);
+		if (overcommit_ratio < 0) {
+			tst_brkm(TBROK, NULL, "-R option is required a"
+				"Non-negative");
+			tst_exit();
+		}
+	}
+
+	setup();
+
+	for (lc = 0; TEST_LOOPING(lc); lc++) {
+		Tst_count = 0;
+
+		overcommit_memory_test();
+	}
+
+	cleanup();
+
+	tst_exit();
+}
+
+void setup(void)
+{
+	long long mem_total, swap_total;
+
+	tst_require_root(NULL);
+
+	tst_sig(NOFORK, DEF_HANDLER, cleanup);
+
+	TEST_PAUSE;
+
+	if (access(FILE_OVER_MEM, F_OK) != 0 ||
+		access(FILE_OVER_RATIO, F_OK) != 0)
+		tst_brkm(TCONF, NULL, "The system "
+			"can't support to test %s", TCID);
+
+	old_overcommit_memory = get_sys_tune(FILE_OVER_MEM);
+	old_overcommit_ratio = get_sys_tune(FILE_OVER_RATIO);
+
+	set_sys_tune(FILE_OVER_RATIO, overcommit_ratio);
+	check_sys_tune(FILE_OVER_RATIO, overcommit_ratio);
+
+	mem_total = read_meminfo("MemTotal:");
+	tst_resm(TINFO, "MemTotal is %lld kB", mem_total);
+	swap_total = read_meminfo("SwapTotal:");
+	tst_resm(TINFO, "SwapTotal is %lld kB", swap_total);
+	sum_total = mem_total + swap_total;
+
+	commit_limit = read_meminfo("CommitLimit:");
+	tst_resm(TINFO, "CommitLimit is %lld kB", commit_limit);
+}
+
+void cleanup(void)
+{
+	set_sys_tune(FILE_OVER_MEM, old_overcommit_memory);
+	set_sys_tune(FILE_OVER_RATIO, old_overcommit_ratio);
+
+	TEST_CLEANUP;
+}
+
+static void usage(void)
+{
+	printf("  -R n    Percentage of overcommitting memory\n");
+}
+
+static void overcommit_memory_test(void)
+{
+	tst_resm(TINFO, "starting test overcommit_memory = 0");
+	set_sys_tune(FILE_OVER_MEM, OVERCOMMIT_GUESS);
+	check_sys_tune(FILE_OVER_MEM, OVERCOMMIT_GUESS);
+
+	update_mem();
+	alloc_and_check(free_total / 2, EXPECT_PASS);
+	update_mem();
+	alloc_and_check(free_total, EXPECT_PASS);
+	update_mem();
+	alloc_and_check(free_total * 2, EXPECT_FAIL);
+
+	tst_resm(TINFO, "starting test overcommit_memory = 1");
+	set_sys_tune(FILE_OVER_MEM, OVERCOMMIT_ALWAYS);
+	check_sys_tune(FILE_OVER_MEM, OVERCOMMIT_ALWAYS);
+
+	alloc_and_check(sum_total / 2, EXPECT_PASS);
+	alloc_and_check(sum_total, EXPECT_PASS);
+	alloc_and_check(sum_total * 2, EXPECT_PASS);
+
+	tst_resm(TINFO, "starting test overcommit_memory = 2");
+	set_sys_tune(FILE_OVER_MEM, OVERCOMMIT_NEVER);
+	check_sys_tune(FILE_OVER_MEM, OVERCOMMIT_NEVER);
+
+	update_mem();
+	alloc_and_check(commit_left / 2, EXPECT_PASS);
+	update_mem();
+	alloc_and_check(commit_left * 2, EXPECT_FAIL);
+	alloc_and_check(commit_limit, EXPECT_FAIL);
+}
+
+static int heavy_malloc(long long size)
+{
+	char *p;
+
+	p = (char *)malloc(size * KB);
+	if (p != NULL) {
+		tst_resm(TINFO, "malloc %lld kB successfully", size);
+		free(p);
+		return 0;
+	} else {
+		tst_resm(TINFO, "malloc %lld kB failed", size);
+		return 1;
+	}
+}
+
+static void alloc_and_check(long long size, int expect_result)
+{
+	int result;
+
+	tst_resm(TINFO, "try to alloc memory = %lld kB", size);
+	result = heavy_malloc(size);
+
+	switch (expect_result) {
+	case EXPECT_PASS:
+		if (result == 0)
+			tst_resm(TPASS, "alloc passed as expected");
+		else
+			tst_resm(TFAIL, "alloc failed, expected to pass");
+		break;
+	case EXPECT_FAIL:
+		if (result != 0)
+			tst_resm(TPASS, "alloc failed as expected");
+		else
+			tst_resm(TFAIL, "alloc passed, expected to fail");
+		break;
+	default:
+		tst_brkm(TBROK, cleanup, "Invaild numbler parameter: %d",
+				expect_result);
+	}
+}
+
+static void update_mem(void)
+{
+	long long mem_free, swap_free;
+	long long committed;
+
+	mem_free = read_meminfo("MemFree:");
+	swap_free = read_meminfo("SwapFree:");
+	free_total = mem_free + swap_free;
+
+	committed = read_meminfo("Committed_AS:");
+	commit_left = commit_limit - committed;
+	if (commit_left < 0)
+		tst_brkm(TBROK, cleanup, "unexpected error:"
+			"CommitLimit > Committed_AS");
+}
-- 
1.7.6

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