[v3] selftests/mm: hugetlb cgroup charging: robustness fixes

[PATCH v3 2/3] selftests/mm/charge_reserved_hugetlb: drop mount size for hugetlbfs

Posted by Li Wang 1 month, 2 weeks ago

charge_reserved_hugetlb.sh mounts a hugetlbfs instance at /mnt/huge with
a fixed size of 256M. On systems with large base hugepages (e.g. 512MB),
this is smaller than a single hugepage, so the hugetlbfs mount ends up
with zero capacity (often visible as size=0 in mount output).

As a result, write_to_hugetlbfs fails with ENOMEM and the test can hang
waiting for progress.

--- Error log ---
  # uname -r
  6.12.0-xxx.el10.aarch64+64k

  #./charge_reserved_hugetlb.sh -cgroup-v2
  # -----------------------------------------
  ...
  # nr hugepages = 10
  # writing cgroup limit: 5368709120
  # writing reseravation limit: 5368709120
  ...
  # write_to_hugetlbfs: Error mapping the file: Cannot allocate memory
  # Waiting for hugetlb memory reservation to reach size 2684354560.
  # 0
  # Waiting for hugetlb memory reservation to reach size 2684354560.
  # 0
  ...

  # mount |grep /mnt/huge
  none on /mnt/huge type hugetlbfs (rw,relatime,seclabel,pagesize=512M,size=0)

  # grep -i huge /proc/meminfo
  ...
  HugePages_Total:      10
  HugePages_Free:       10
  HugePages_Rsvd:        0
  HugePages_Surp:        0
  Hugepagesize:     524288 kB
  Hugetlb:         5242880 kB

Drop the mount args with 'size=256M', so the filesystem capacity is sufficient
regardless of HugeTLB page size.

Fixes: 29750f71a9 ("hugetlb_cgroup: add hugetlb_cgroup reservation tests")
Signed-off-by: Li Wang <liwang@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Waiman Long <longman@redhat.com>
---
 tools/testing/selftests/mm/charge_reserved_hugetlb.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
index e1fe16bcbbe8..fa6713892d82 100755
--- a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
+++ b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
@@ -290,7 +290,7 @@ function run_test() {
   setup_cgroup "hugetlb_cgroup_test" "$cgroup_limit" "$reservation_limit"
 
   mkdir -p /mnt/huge
-  mount -t hugetlbfs -o pagesize=${MB}M,size=256M none /mnt/huge
+  mount -t hugetlbfs -o pagesize=${MB}M none /mnt/huge
 
   write_hugetlbfs_and_get_usage "hugetlb_cgroup_test" "$size" "$populate" \
     "$write" "/mnt/huge/test" "$method" "$private" "$expect_failure" \
@@ -344,7 +344,7 @@ function run_multiple_cgroup_test() {
   setup_cgroup "hugetlb_cgroup_test2" "$cgroup_limit2" "$reservation_limit2"
 
   mkdir -p /mnt/huge
-  mount -t hugetlbfs -o pagesize=${MB}M,size=256M none /mnt/huge
+  mount -t hugetlbfs -o pagesize=${MB}M none /mnt/huge
 
   write_hugetlbfs_and_get_usage "hugetlb_cgroup_test1" "$size1" \
     "$populate1" "$write1" "/mnt/huge/test1" "$method" "$private" \
-- 
2.49.0

Re: [PATCH v3 2/3] selftests/mm/charge_reserved_hugetlb: drop mount size for hugetlbfs

Posted by Waiman Long 1 month, 2 weeks ago

On 12/21/25 7:26 AM, Li Wang wrote:
> charge_reserved_hugetlb.sh mounts a hugetlbfs instance at /mnt/huge with
> a fixed size of 256M. On systems with large base hugepages (e.g. 512MB),
> this is smaller than a single hugepage, so the hugetlbfs mount ends up
> with zero capacity (often visible as size=0 in mount output).
>
> As a result, write_to_hugetlbfs fails with ENOMEM and the test can hang
> waiting for progress.
>
> --- Error log ---
>    # uname -r
>    6.12.0-xxx.el10.aarch64+64k
>
>    #./charge_reserved_hugetlb.sh -cgroup-v2
>    # -----------------------------------------
>    ...
>    # nr hugepages = 10
>    # writing cgroup limit: 5368709120
>    # writing reseravation limit: 5368709120
>    ...
>    # write_to_hugetlbfs: Error mapping the file: Cannot allocate memory
>    # Waiting for hugetlb memory reservation to reach size 2684354560.
>    # 0
>    # Waiting for hugetlb memory reservation to reach size 2684354560.
>    # 0
>    ...
>
>    # mount |grep /mnt/huge
>    none on /mnt/huge type hugetlbfs (rw,relatime,seclabel,pagesize=512M,size=0)
>
>    # grep -i huge /proc/meminfo
>    ...
>    HugePages_Total:      10
>    HugePages_Free:       10
>    HugePages_Rsvd:        0
>    HugePages_Surp:        0
>    Hugepagesize:     524288 kB
>    Hugetlb:         5242880 kB
>
> Drop the mount args with 'size=256M', so the filesystem capacity is sufficient
> regardless of HugeTLB page size.
>
> Fixes: 29750f71a9 ("hugetlb_cgroup: add hugetlb_cgroup reservation tests")
> Signed-off-by: Li Wang <liwang@redhat.com>
> Cc: David Hildenbrand <david@kernel.org>
> Cc: Mark Brown <broonie@kernel.org>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: Waiman Long <longman@redhat.com>
> ---
>   tools/testing/selftests/mm/charge_reserved_hugetlb.sh | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
> index e1fe16bcbbe8..fa6713892d82 100755
> --- a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
> +++ b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
> @@ -290,7 +290,7 @@ function run_test() {
>     setup_cgroup "hugetlb_cgroup_test" "$cgroup_limit" "$reservation_limit"
>   
>     mkdir -p /mnt/huge
> -  mount -t hugetlbfs -o pagesize=${MB}M,size=256M none /mnt/huge
> +  mount -t hugetlbfs -o pagesize=${MB}M none /mnt/huge
>   
>     write_hugetlbfs_and_get_usage "hugetlb_cgroup_test" "$size" "$populate" \
>       "$write" "/mnt/huge/test" "$method" "$private" "$expect_failure" \
> @@ -344,7 +344,7 @@ function run_multiple_cgroup_test() {
>     setup_cgroup "hugetlb_cgroup_test2" "$cgroup_limit2" "$reservation_limit2"
>   
>     mkdir -p /mnt/huge
> -  mount -t hugetlbfs -o pagesize=${MB}M,size=256M none /mnt/huge
> +  mount -t hugetlbfs -o pagesize=${MB}M none /mnt/huge
>   
>     write_hugetlbfs_and_get_usage "hugetlb_cgroup_test1" "$size1" \
>       "$populate1" "$write1" "/mnt/huge/test1" "$method" "$private" \
Acked-by: Waiman Long <longman@redhat.com>

Re: [PATCH v3 2/3] selftests/mm/charge_reserved_hugetlb: drop mount size for hugetlbfs

Posted by David Hildenbrand (Red Hat) 1 month, 2 weeks ago

On 12/21/25 13:26, Li Wang wrote:
> charge_reserved_hugetlb.sh mounts a hugetlbfs instance at /mnt/huge with
> a fixed size of 256M. On systems with large base hugepages (e.g. 512MB),
> this is smaller than a single hugepage, so the hugetlbfs mount ends up
> with zero capacity (often visible as size=0 in mount output).
> 
> As a result, write_to_hugetlbfs fails with ENOMEM and the test can hang
> waiting for progress.
> 
> --- Error log ---
>    # uname -r
>    6.12.0-xxx.el10.aarch64+64k
> 
>    #./charge_reserved_hugetlb.sh -cgroup-v2
>    # -----------------------------------------
>    ...
>    # nr hugepages = 10
>    # writing cgroup limit: 5368709120
>    # writing reseravation limit: 5368709120
>    ...
>    # write_to_hugetlbfs: Error mapping the file: Cannot allocate memory
>    # Waiting for hugetlb memory reservation to reach size 2684354560.
>    # 0
>    # Waiting for hugetlb memory reservation to reach size 2684354560.
>    # 0
>    ...
> 
>    # mount |grep /mnt/huge
>    none on /mnt/huge type hugetlbfs (rw,relatime,seclabel,pagesize=512M,size=0)
> 
>    # grep -i huge /proc/meminfo
>    ...
>    HugePages_Total:      10
>    HugePages_Free:       10
>    HugePages_Rsvd:        0
>    HugePages_Surp:        0
>    Hugepagesize:     524288 kB
>    Hugetlb:         5242880 kB
> 
> Drop the mount args with 'size=256M', so the filesystem capacity is sufficient
> regardless of HugeTLB page size.
> 
> Fixes: 29750f71a9 ("hugetlb_cgroup: add hugetlb_cgroup reservation tests")

Likely Andrew should add a CC of stable

Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>

-- 
Cheers

David

Re: [PATCH v3 2/3] selftests/mm/charge_reserved_hugetlb: drop mount size for hugetlbfs

Posted by Andrew Morton 1 month, 2 weeks ago

On Mon, 22 Dec 2025 11:01:17 +0100 "David Hildenbrand (Red Hat)" <david@kernel.org> wrote:

> > Fixes: 29750f71a9 ("hugetlb_cgroup: add hugetlb_cgroup reservation tests")
> 
> Likely Andrew should add a CC of stable
> 

yep, thanks.