On Wed, Sep 16, 2020 at 10:11 AM Randy Dunlap [off-list ref] wrote:

Hi,
Please see comments below.

On 9/15/20 5:59 AM, Muchun Song wrote:

quoted

Add a kernel parameter hugetlb_free_vmemmap to disable the feature of
freeing unused vmemmap pages associated with each hugetlb page on boot.

Signed-off-by: Muchun Song <redacted>
---
 .../admin-guide/kernel-parameters.txt         |  9 ++++++++
 Documentation/admin-guide/mm/hugetlbpage.rst  |  3 +++
 mm/hugetlb.c                                  | 23 +++++++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 5debfe238027..69d18ef6f66b 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt

@@ -1551,6 +1551,15 @@
                      Documentation/admin-guide/mm/hugetlbpage.rst.
                      Format: size[KMG]

+     hugetlb_free_vmemmap=
+                     [KNL] When CONFIG_HUGETLB_PAGE_FREE_VMEMMAP is set,
+                     this disables freeing unused vmemmap pages associated

                        this controls

quoted

+                     each HugeTLB page.

                        with each HugeTLB page.

quoted

+                     Format: { on (default) | off }
+
+                     on:  enable the feature
+                     off: dosable the feature

                             disable

quoted

+
      hung_task_panic=
                      [KNL] Should the hung task detector generate panics.
                      Format: 0 | 1

diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst
index f7b1c7462991..7d6129ee97dd 100644
--- a/Documentation/admin-guide/mm/hugetlbpage.rst
+++ b/Documentation/admin-guide/mm/hugetlbpage.rst

@@ -145,6 +145,9 @@ default_hugepagesz

      will all result in 256 2M huge pages being allocated.  Valid default
      huge page size is architecture dependent.

insert blank line here.

quoted

+hugetlb_free_vmemmap
+     When CONFIG_HUGETLB_PAGE_FREE_VMEMMAP is set, this disables freeing
+     unused vmemmap pages associated each HugeTLB page.

 When multiple huge page sizes are supported, ``/proc/sys/vm/nr_hugepages``
 indicates the current number of pre-allocated huge pages of the default size.

Thanks for your comments.

--
~Randy

-- 
Yours,
Muchun