linux-kernel - [PATCH 3/3] selftests: Set overcommit_policy as OVERCOMMIT

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Message-Id: <20230314042351.13134-4-chaitanyas.prakash@arm.com>
Date:   Tue, 14 Mar 2023 09:53:51 +0530
From:   Chaitanya S Prakash <chaitanyas.prakash@....com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Chaitanya S Prakash <chaitanyas.prakash@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org
Subject: [PATCH 3/3] selftests: Set overcommit_policy as OVERCOMMIT_ALWAYS

The kernel's default behaviour is to obstruct the allocation of high
virtual address as it handles memory overcommit in a heuristic manner.
Setting the parameter as OVERCOMMIT_ALWAYS, ensures kernel isn't
susceptible to the availability of a platform's physical memory when
denying a memory allocation request.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Shuah Khan <shuah@...nel.org>
Cc: linux-mm@...ck.org
Cc: linux-kselftest@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Chaitanya S Prakash <chaitanyas.prakash@....com>
---
 tools/testing/selftests/mm/run_vmtests.sh | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index 8984e0bb58c7..c0f93b668c0c 100644
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -220,7 +220,15 @@ CATEGORY="mremap" run_test ./mremap_test
 CATEGORY="hugetlb" run_test ./thuge-gen
 
 if [ $VADDR64 -ne 0 ]; then
+
+	# set overcommit_policy as OVERCOMMIT_ALWAYS so that kernel
+	# allows high virtual address allocation requests independent
+	# of platform's physical memory.
+
+	prev_policy=$(cat /proc/sys/vm/overcommit_memory)
+	echo 1 > /proc/sys/vm/overcommit_memory
 	CATEGORY="hugevm" run_test ./virtual_address_range
+	echo $prev_policy > /proc/sys/vm/overcommit_memory
 
 	# virtual address 128TB switch test
 	CATEGORY="hugevm" run_test ./va_128TBswitch.sh
-- 
2.30.2