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Message-ID: <CAMZfGtV5uSkNcoS1sKdOOwWXr6TaroRj_kJjJ7iqnF=NMnZ8NA@mail.gmail.com>
Date: Tue, 24 Nov 2020 19:07:56 +0800
From: Muchun Song <songmuchun@...edance.com>
To: "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>
Cc: "corbet@....net" <corbet@....net>,
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Subject: Re: [External] RE: [PATCH v6 14/16] mm/hugetlb: Add a kernel
parameter hugetlb_free_vmemmap
On Tue, Nov 24, 2020 at 6:54 PM Song Bao Hua (Barry Song)
<song.bao.hua@...ilicon.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Muchun Song [mailto:songmuchun@...edance.com]
> > Sent: Tuesday, November 24, 2020 10:53 PM
> > To: corbet@....net; mike.kravetz@...cle.com; tglx@...utronix.de;
> > mingo@...hat.com; bp@...en8.de; x86@...nel.org; hpa@...or.com;
> > dave.hansen@...ux.intel.com; luto@...nel.org; peterz@...radead.org;
> > viro@...iv.linux.org.uk; akpm@...ux-foundation.org; paulmck@...nel.org;
> > mchehab+huawei@...nel.org; pawan.kumar.gupta@...ux.intel.com;
> > rdunlap@...radead.org; oneukum@...e.com; anshuman.khandual@....com;
> > jroedel@...e.de; almasrymina@...gle.com; rientjes@...gle.com;
> > willy@...radead.org; osalvador@...e.de; mhocko@...e.com; Song Bao Hua
> > (Barry Song) <song.bao.hua@...ilicon.com>
> > Cc: duanxiongchun@...edance.com; linux-doc@...r.kernel.org;
> > linux-kernel@...r.kernel.org; linux-mm@...ck.org;
> > linux-fsdevel@...r.kernel.org; Muchun Song <songmuchun@...edance.com>
> > 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 <songmuchun@...edance.com>
> > ---
> > 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
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