From: Mike Kravetz <mike.kravetz@oracle.com>
To: Yosry Ahmed <yosryahmed@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Shuah Khan <shuah@kernel.org>,
linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org,
Mina Almasry <almasrymina@google.com>
Subject: Re: [PATCH] mm, hugepages: fix size in hugetlb mremap() test
Date: Tue, 23 Nov 2021 19:42:48 -0800 [thread overview]
Message-ID: <a87c5768-9bd3-a2f5-7eb5-d2813b958514@oracle.com> (raw)
In-Reply-To: <CAJD7tkYZY1g_b9E4ZP3yqHhT36nF57c4bzKRQM-SLftDCYNQ9A@mail.gmail.com>
On 11/23/21 18:19, Yosry Ahmed wrote:
> On Tue, Nov 23, 2021 at 5:08 PM Mike Kravetz <mike.kravetz@oracle.com> wrote:
>>
>> On 11/23/21 12:46, Yosry Ahmed wrote:
>>> The hugetlb vma mremap() test mentions in the header comment that it
>>> uses 10MB worth of huge pages, when it actually uses 1GB. This causes
>>> the test to fail on devices with smaller memories.
>>>
>>> Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
>>> ---
>>> tools/testing/selftests/vm/hugepage-mremap.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> I'll let Mina comment, but I think I know what happened.
>
> Thanks for taking the time to review this and explain what happened.
>
>>
>>
>> The original version of the test did indeed use 10MB. However, the mremap
>> code must 'unshare' and shared pmd mappings before remapping. Since sharing
>> requires mappings of at least 1GB, the size was changed to make sure unsharing
>> worked.
>>
>> In the end, I believe I suggested adding hugepage-mremap to run_vmtests.sh.
>> The script does not try to configure a GB worth of huge pages. And, I think
>> it is somewhat unreasonable to suggest users gave a spare GB to run the test.
>
> Alternatively, we can pass an optional argument to the test that makes it use
> 1GB instead of 10MB. This way, if the test is run with run_vmtests.sh the
> default behavior would be to use 10MB, making sure users do not run out of
> memory. Otherwise, an interested user could run the test without run_vmtest.sh
> and provide the extra argument to make the test use 1GB and make sure that
> unsharing works correctly. Thoughts?
>
Passing a 'mapping size' argument as you suggest would be best. That way
run_vmtest.sh can pass in a size such as 10MB, but the test could be used
independently with arbitrary size mappings.
If you have the time to do this, go for it!
--
Mike Kravetz
next prev parent reply other threads:[~2021-11-24 3:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-23 20:46 Yosry Ahmed
2021-11-24 1:08 ` Mike Kravetz
2021-11-24 2:19 ` Yosry Ahmed
2021-11-24 3:42 ` Mike Kravetz [this message]
2021-11-24 21:03 ` Mina Almasry
2021-11-24 20:38 ` [PATCH] mm, hugepages: make memory size variable in hugepage-mremap selftest Yosry Ahmed
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