[v3] selftests/mm: fix failures and robustness improvements

[PATCH v3 06/13] selftest/mm: adjust hugepage-mremap test size for large huge pages

Posted by Sayali Patil 6 days, 9 hours ago

The hugepage-mremap selftest uses a default size of 10MB, which is
sufficient for small huge page sizes. However, when the huge page size
is large (e.g. 1GB), 10MB is smaller than a single huge page.
As a result, the test does not trigger PMD sharing and the
corresponding unshare path in mremap(), causing the
test to fail (mremap succeeds where a failure is expected).

Update run_vmtest.sh to use twice the huge page size when the huge page
size exceeds 10MB, while retaining the 10MB default for smaller huge
pages. This ensures the test exercises the intended PMD sharing and
unsharing paths for larger huge page sizes.

Before patch:
 running ./hugepage-mremap
 ------------------------------
 TAP version 13
 1..1
  Map haddr: Returned address is 0x7eaa40000000
  Map daddr: Returned address is 0x7daa40000000
  Map vaddr: Returned address is 0x7faa40000000
  Address returned by mmap() = 0x7fffaa600000
  Mremap: Returned address is 0x7faa40000000
  First hex is 0
  First hex is 3020100
 Bail out! mremap: Expected failure, but call succeeded
 Planned tests != run tests (1 != 0)
 Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
 [FAIL]
 not ok 1 hugepage-mremap # exit=1

Before patch:
 running ./hugepage-mremap
 ------------------------------
 TAP version 13
 1..1
  Map haddr: Returned address is 0x7eaa40000000
  Map daddr: Returned address is 0x7daa40000000
  Map vaddr: Returned address is 0x7faa40000000
  Address returned by mmap() = 0x7fffaa600000
  Mremap: Returned address is 0x7faa40000000
  First hex is 0
  First hex is 3020100
 Bail out! mremap: Expected failure, but call succeeded
 Planned tests != run tests (1 != 0)
 Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
 [FAIL]
 not ok 1 hugepage-mremap # exit=1

After patch:
 running ./hugepage-mremap 2048
 ------------------------------
 TAP version 13
 1..1
  Map haddr: Returned address is 0x7eaa40000000
  Map daddr: Returned address is 0x7daa40000000
  Map vaddr: Returned address is 0x7faa40000000
  Address returned by mmap() = 0x7fff13000000
  Mremap: Returned address is 0x7faa40000000
  First hex is 0
  First hex is 3020100
  ok 1 Read same data
 Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
 [PASS]
 ok 1 hugepage-mremap 2048

Fixes: f77a286de48c ("mm, hugepages: make memory size variable in hugepage-mremap selftest")
Acked-by: Zi Yan <ziy@nvidia.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
---
 tools/testing/selftests/mm/run_vmtests.sh | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index afdcfd0d7cef..eecec0b6eb13 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -293,7 +293,18 @@ echo "$shmmax" > /proc/sys/kernel/shmmax
 echo "$shmall" > /proc/sys/kernel/shmall
 
 CATEGORY="hugetlb" run_test ./map_hugetlb
-CATEGORY="hugetlb" run_test ./hugepage-mremap
+
+# If the huge page size is larger than 10MB, increase the test memory size
+# to twice the huge page size (in MB) to ensure the test exercises PMD sharing
+# and the unshare path in hugepage-mremap. Otherwise, run the test with
+# the default 10MB memory size.
+if [ "$hpgsize_KB" -gt 10240 ]; then
+	len_mb=$(( (2 * hpgsize_KB) / 1024 ))
+	CATEGORY="hugetlb" run_test ./hugepage-mremap "${len_mb}"
+else
+	CATEGORY="hugetlb" run_test ./hugepage-mremap
+fi
+
 CATEGORY="hugetlb" run_test ./hugepage-vmemmap
 CATEGORY="hugetlb" run_test ./hugetlb-madvise
 CATEGORY="hugetlb" run_test ./hugetlb_dio
-- 
2.52.0

Re: [PATCH v3 06/13] selftest/mm: adjust hugepage-mremap test size for large huge pages

Posted by David Hildenbrand (Arm) 1 day, 2 hours ago

On 3/27/26 08:16, Sayali Patil wrote:
> The hugepage-mremap selftest uses a default size of 10MB, which is
> sufficient for small huge page sizes. However, when the huge page size
> is large (e.g. 1GB), 10MB is smaller than a single huge page.
> As a result, the test does not trigger PMD sharing and the
> corresponding unshare path in mremap(), causing the
> test to fail (mremap succeeds where a failure is expected).
> 
> Update run_vmtest.sh to use twice the huge page size when the huge page
> size exceeds 10MB, while retaining the 10MB default for smaller huge
> pages. This ensures the test exercises the intended PMD sharing and
> unsharing paths for larger huge page sizes.
> 
> Before patch:
>  running ./hugepage-mremap
>  ------------------------------
>  TAP version 13
>  1..1
>   Map haddr: Returned address is 0x7eaa40000000
>   Map daddr: Returned address is 0x7daa40000000
>   Map vaddr: Returned address is 0x7faa40000000
>   Address returned by mmap() = 0x7fffaa600000
>   Mremap: Returned address is 0x7faa40000000
>   First hex is 0
>   First hex is 3020100
>  Bail out! mremap: Expected failure, but call succeeded
>  Planned tests != run tests (1 != 0)
>  Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
>  [FAIL]
>  not ok 1 hugepage-mremap # exit=1
> 
> Before patch:
>  running ./hugepage-mremap
>  ------------------------------
>  TAP version 13
>  1..1
>   Map haddr: Returned address is 0x7eaa40000000
>   Map daddr: Returned address is 0x7daa40000000
>   Map vaddr: Returned address is 0x7faa40000000
>   Address returned by mmap() = 0x7fffaa600000
>   Mremap: Returned address is 0x7faa40000000
>   First hex is 0
>   First hex is 3020100
>  Bail out! mremap: Expected failure, but call succeeded
>  Planned tests != run tests (1 != 0)
>  Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
>  [FAIL]
>  not ok 1 hugepage-mremap # exit=1
> 

Why are there two "Before patch" in here?

> After patch:
>  running ./hugepage-mremap 2048
>  ------------------------------
>  TAP version 13
>  1..1
>   Map haddr: Returned address is 0x7eaa40000000
>   Map daddr: Returned address is 0x7daa40000000
>   Map vaddr: Returned address is 0x7faa40000000
>   Address returned by mmap() = 0x7fff13000000
>   Mremap: Returned address is 0x7faa40000000
>   First hex is 0
>   First hex is 3020100
>   ok 1 Read same data
>  Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
>  [PASS]
>  ok 1 hugepage-mremap 2048
> 
> Fixes: f77a286de48c ("mm, hugepages: make memory size variable in hugepage-mremap selftest")
> Acked-by: Zi Yan <ziy@nvidia.com>
> Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
> Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
> ---
>  tools/testing/selftests/mm/run_vmtests.sh | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
> index afdcfd0d7cef..eecec0b6eb13 100755
> --- a/tools/testing/selftests/mm/run_vmtests.sh
> +++ b/tools/testing/selftests/mm/run_vmtests.sh
> @@ -293,7 +293,18 @@ echo "$shmmax" > /proc/sys/kernel/shmmax
>  echo "$shmall" > /proc/sys/kernel/shmall
>  
>  CATEGORY="hugetlb" run_test ./map_hugetlb
> -CATEGORY="hugetlb" run_test ./hugepage-mremap
> +
> +# If the huge page size is larger than 10MB, increase the test memory size
> +# to twice the huge page size (in MB) to ensure the test exercises PMD sharing
> +# and the unshare path in hugepage-mremap. Otherwise, run the test with
> +# the default 10MB memory size.

PMD sharing requires, on x86, a 1 GiB area with 2 MiB hugetlb folios.

How does doubling sort that out?

Also, why the magic value 10mb?


-- 
Cheers,

David

Re: [PATCH v3 06/13] selftest/mm: adjust hugepage-mremap test size for large huge pages

Posted by Sayali Patil 20 hours ago


On 01/04/26 19:40, David Hildenbrand (Arm) wrote:
> On 3/27/26 08:16, Sayali Patil wrote:
>> The hugepage-mremap selftest uses a default size of 10MB, which is
>> sufficient for small huge page sizes. However, when the huge page size
>> is large (e.g. 1GB), 10MB is smaller than a single huge page.
>> As a result, the test does not trigger PMD sharing and the
>> corresponding unshare path in mremap(), causing the
>> test to fail (mremap succeeds where a failure is expected).
>>
>> Update run_vmtest.sh to use twice the huge page size when the huge page
>> size exceeds 10MB, while retaining the 10MB default for smaller huge
>> pages. This ensures the test exercises the intended PMD sharing and
>> unsharing paths for larger huge page sizes.
>>
>> Before patch:
>>   running ./hugepage-mremap
>>   ------------------------------
>>   TAP version 13
>>   1..1
>>    Map haddr: Returned address is 0x7eaa40000000
>>    Map daddr: Returned address is 0x7daa40000000
>>    Map vaddr: Returned address is 0x7faa40000000
>>    Address returned by mmap() = 0x7fffaa600000
>>    Mremap: Returned address is 0x7faa40000000
>>    First hex is 0
>>    First hex is 3020100
>>   Bail out! mremap: Expected failure, but call succeeded
>>   Planned tests != run tests (1 != 0)
>>   Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
>>   [FAIL]
>>   not ok 1 hugepage-mremap # exit=1
>>
>> Before patch:
>>   running ./hugepage-mremap
>>   ------------------------------
>>   TAP version 13
>>   1..1
>>    Map haddr: Returned address is 0x7eaa40000000
>>    Map daddr: Returned address is 0x7daa40000000
>>    Map vaddr: Returned address is 0x7faa40000000
>>    Address returned by mmap() = 0x7fffaa600000
>>    Mremap: Returned address is 0x7faa40000000
>>    First hex is 0
>>    First hex is 3020100
>>   Bail out! mremap: Expected failure, but call succeeded
>>   Planned tests != run tests (1 != 0)
>>   Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
>>   [FAIL]
>>   not ok 1 hugepage-mremap # exit=1
>>
> 
> Why are there two "Before patch" in here?
Thanks for pointing that out, Let me fix it in the next version.
> 
>> After patch:
>>   running ./hugepage-mremap 2048
>>   ------------------------------
>>   TAP version 13
>>   1..1
>>    Map haddr: Returned address is 0x7eaa40000000
>>    Map daddr: Returned address is 0x7daa40000000
>>    Map vaddr: Returned address is 0x7faa40000000
>>    Address returned by mmap() = 0x7fff13000000
>>    Mremap: Returned address is 0x7faa40000000
>>    First hex is 0
>>    First hex is 3020100
>>    ok 1 Read same data
>>   Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
>>   [PASS]
>>   ok 1 hugepage-mremap 2048
>>
>> Fixes: f77a286de48c ("mm, hugepages: make memory size variable in hugepage-mremap selftest")
>> Acked-by: Zi Yan <ziy@nvidia.com>
>> Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
>> Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
>> ---
>>   tools/testing/selftests/mm/run_vmtests.sh | 13 ++++++++++++-
>>   1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
>> index afdcfd0d7cef..eecec0b6eb13 100755
>> --- a/tools/testing/selftests/mm/run_vmtests.sh
>> +++ b/tools/testing/selftests/mm/run_vmtests.sh
>> @@ -293,7 +293,18 @@ echo "$shmmax" > /proc/sys/kernel/shmmax
>>   echo "$shmall" > /proc/sys/kernel/shmall
>>   
>>   CATEGORY="hugetlb" run_test ./map_hugetlb
>> -CATEGORY="hugetlb" run_test ./hugepage-mremap
>> +
>> +# If the huge page size is larger than 10MB, increase the test memory size
>> +# to twice the huge page size (in MB) to ensure the test exercises PMD sharing
>> +# and the unshare path in hugepage-mremap. Otherwise, run the test with
>> +# the default 10MB memory size.
> 
> PMD sharing requires, on x86, a 1 GiB area with 2 MiB hugetlb folios.
> 
> How does doubling sort that out?
> 
> Also, why the magic value 10mb?
> 
> 
Hi David,
Yes, 1GB huge pages are mapped at the PUD level and are not involved in 
PMD sharing, as huge_pte_alloc() skips sharing for sizes other than 
PMD_SIZE.

The issue here is due to an unaligned memory size on a 1GB mapping.
This leads munmap() to fail at an unaligned address, causing the 
subsequent expected-to-fail mremap() to unexpectedly succeed.
The default memory size for this test is 10MB.

Aligning the size to a multiple of 1GB avoids this failure, but it is 
not related to PMD sharing. I will update the description in v4 to 
reflect this more accurately.

I will also update the test code directly to align the memory size to 
the huge page size, rather than modifying run_vmtests.sh.

Thanks,
Sayali