On Tue, Nov 24, 2020 at 6:54 PM Song Bao Hua (Barry Song)
<[email protected]> wrote:
>
>
>
> > -----Original Message-----
> > From: Muchun Song [mailto:[email protected]]
> > Sent: Tuesday, November 24, 2020 10:53 PM
> > To: [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected];
> > [email protected]; [email protected]; [email protected]; Song Bao Hua
> > (Barry Song) <[email protected]>
> > Cc: [email protected]; [email protected];
> > [email protected]; [email protected];
> > [email protected]; Muchun Song <[email protected]>
> > Subject: [PATCH v6 14/16] mm/hugetlb: Add a kernel parameter
> > hugetlb_free_vmemmap
> >
> > 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 <[email protected]>
> > ---
> > Documentation/admin-guide/kernel-parameters.txt | 9 +++++++++
> > Documentation/admin-guide/mm/hugetlbpage.rst | 3 +++
> > mm/hugetlb_vmemmap.c | 19
> > ++++++++++++++++++-
> > 3 files changed, 30 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt
> > b/Documentation/admin-guide/kernel-parameters.txt
> > index 5debfe238027..d28c3acde965 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 controls freeing unused vmemmap pages associated
> > + with each HugeTLB page.
> > + Format: { on | off (default) }
> > +
> > + on: enable the feature
> > + off: disable the feature
> > +
>
> We've a parameter here. but wouldn't it be applied to "x86/mm/64/:disable
> Pmd page mapping of vmemmap" as well?
> If (hugetlb_free_vmemmap_enabled)
> Do Basepage mapping?
Oh, yeah, we can. Thanks.
>
> > 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..6a8b57f6d3b7 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.
> > +hugetlb_free_vmemmap
> > + When CONFIG_HUGETLB_PAGE_FREE_VMEMMAP is set, this enables
> > 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.
> > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> > index 509ca451e232..b2222f8d1245 100644
> > --- a/mm/hugetlb_vmemmap.c
> > +++ b/mm/hugetlb_vmemmap.c
> > @@ -131,6 +131,22 @@ typedef void (*vmemmap_pte_remap_func_t)(struct
> > page *reuse, pte_t *ptep,
> > unsigned long start, unsigned long
> > end,
> > void *priv);
> >
> > +static bool hugetlb_free_vmemmap_enabled __initdata;
> > +
> > +static int __init early_hugetlb_free_vmemmap_param(char *buf)
> > +{
> > + if (!buf)
> > + return -EINVAL;
> > +
> > + if (!strcmp(buf, "on"))
> > + hugetlb_free_vmemmap_enabled = true;
> > + else if (strcmp(buf, "off"))
> > + return -EINVAL;
> > +
> > + return 0;
> > +}
> > +early_param("hugetlb_free_vmemmap",
> > early_hugetlb_free_vmemmap_param);
> > +
> > static inline unsigned int vmemmap_pages_per_hpage(struct hstate *h)
> > {
> > return free_vmemmap_pages_per_hpage(h) + RESERVE_VMEMMAP_NR;
> > @@ -322,7 +338,8 @@ void __init hugetlb_vmemmap_init(struct hstate *h)
> > unsigned int order = huge_page_order(h);
> > unsigned int vmemmap_pages;
> >
> > - if (!is_power_of_2(sizeof(struct page))) {
> > + if (!is_power_of_2(sizeof(struct page)) ||
> > + !hugetlb_free_vmemmap_enabled) {
> > pr_info("disable freeing vmemmap pages for %s\n", h->name);
> > return;
> > }
> > --
> > 2.11.0
>
> Thanks
> Barry
>
--
Yours,
Muchun
