linux-kernel - Re: [PATCH 1/1] selftests/mm: new test that steals pages

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Message-ID: <ZZ5g5iM5+xfw1pJ6@gmail.com>
Date: Wed, 10 Jan 2024 01:18:30 -0800
From: Breno Leitao <leitao@...ian.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: riel@...riel.com, linux-mm@...ck.org, Shuah Khan <shuah@...nel.org>,
	vegard.nossum@...cle.com, rppt@...nel.org, songmuchun@...edance.com,
	shy828301@...il.com, linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] selftests/mm: new test that steals pages

On Tue, Jan 09, 2024 at 09:47:31PM -0800, Andrew Morton wrote:
> On Fri,  5 Jan 2024 07:54:19 -0800 Breno Leitao <leitao@...ian.org> wrote:
> 
> > This test stresses the race between of madvise(DONTNEED), a page fault
> > and a parallel huge page mmap, which should fail due to lack of
> > available page available for mapping.
> > 
> > This test case must run on a system with one and only one huge page
> > available.
> > 
> > 	# echo 1 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
> 
> Can't the test framework perform this configuration prior to running
> the test?

We have this infrastructure already set in the run_vmtest.sh.
The "hugetlb_fault_after_madv" selftest needs the same configuration,
so, once the fix is ready, we will just add something as:

	--- a/tools/testing/selftests/mm/run_vmtests.sh
	+++ b/tools/testing/selftests/mm/run_vmtests.sh
	@@ -227,6 +227,7 @@ nr_hugepages_tmp=$(cat /proc/sys/vm/nr_hugepages)
	 # For this test, we need one and just one huge page
	 echo 1 > /proc/sys/vm/nr_hugepages
	 CATEGORY="hugetlb" run_test ./hugetlb_fault_after_madv
	+CATEGORY="hugetlb" run_test ./hugetlb_madv_vs_map
	 # Restore the previous number of huge pages, since further tests rely on it
	 echo "$nr_hugepages_tmp" > /proc/sys/vm/nr_hugepages