Re: [External] Re: [PATCH v13 02/12] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP
On Tue, 26 Jan 2021, Muchun Song wrote: > > I'm not sure that Kconfig is the right place to document functional > > behavior of the kernel, especially for non-configurable options. Seems > > like this is already served by existing comments added by this patch > > series in the files where the description is helpful. > > OK. So do you mean just remove the help text here? > Yeah, I'd suggest removing the help text from a non-configurable Kconfig option and double checking that its substance is available elsewhere (like the giant comment in mm/hugetlb_vmemmap.c).
Re: [External] Re: [PATCH v13 02/12] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP
On Tue, Jan 26, 2021 at 2:47 AM David Rientjes wrote: > > On Mon, 25 Jan 2021, Muchun Song wrote: > > > > >> I'm not sure I understand the rationale for providing this help text if > > > >> this is def_bool depending on CONFIG_HUGETLB_PAGE. Are you intending > > > >> that > > > >> this is actually configurable and we want to provide guidance to the > > > >> admin > > > >> on when to disable it (which it currently doesn't)? If not, why have > > > >> the > > > >> help text? > > > > > > > > This is __not__ configurable. Seems like a comment to help others > > > > understand this option. Like Randy said. > > > > > > Yes, it could be written with '#' (or "comment") comment syntax instead > > > of as help text. > > > > Got it. I will update in the next version. Thanks. > > > > I'm not sure that Kconfig is the right place to document functional > behavior of the kernel, especially for non-configurable options. Seems > like this is already served by existing comments added by this patch > series in the files where the description is helpful. OK. So do you mean just remove the help text here? Thanks.
Re: [External] Re: [PATCH v13 02/12] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP
On Mon, 25 Jan 2021, Muchun Song wrote: > > >> I'm not sure I understand the rationale for providing this help text if > > >> this is def_bool depending on CONFIG_HUGETLB_PAGE. Are you intending > > >> that > > >> this is actually configurable and we want to provide guidance to the > > >> admin > > >> on when to disable it (which it currently doesn't)? If not, why have the > > >> help text? > > > > > > This is __not__ configurable. Seems like a comment to help others > > > understand this option. Like Randy said. > > > > Yes, it could be written with '#' (or "comment") comment syntax instead of > > as help text. > > Got it. I will update in the next version. Thanks. > I'm not sure that Kconfig is the right place to document functional behavior of the kernel, especially for non-configurable options. Seems like this is already served by existing comments added by this patch series in the files where the description is helpful.
Re: [External] Re: [PATCH v13 02/12] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP
On Mon, Jan 25, 2021 at 12:09 PM Randy Dunlap wrote:
>
> On 1/24/21 8:06 PM, Muchun Song wrote:
> > On Mon, Jan 25, 2021 at 7:58 AM David Rientjes wrote:
> >>
> >>
> >> On Sun, 17 Jan 2021, Muchun Song wrote:
> >>
> >>> The HUGETLB_PAGE_FREE_VMEMMAP option is used to enable the freeing
> >>> of unnecessary vmemmap associated with HugeTLB pages. The config
> >>> option is introduced early so that supporting code can be written
> >>> to depend on the option. The initial version of the code only
> >>> provides support for x86-64.
> >>>
> >>> Like other code which frees vmemmap, this config option depends on
> >>> HAVE_BOOTMEM_INFO_NODE. The routine register_page_bootmem_info() is
> >>> used to register bootmem info. Therefore, make sure
> >>> register_page_bootmem_info is enabled if HUGETLB_PAGE_FREE_VMEMMAP
> >>> is defined.
> >>>
> >>> Signed-off-by: Muchun Song
> >>> Reviewed-by: Oscar Salvador
> >>> Acked-by: Mike Kravetz
> >>> ---
> >>> arch/x86/mm/init_64.c | 2 +-
> >>> fs/Kconfig| 18 ++
> >>> 2 files changed, 19 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> >>> index 0a45f062826e..0435bee2e172 100644
> >>> --- a/arch/x86/mm/init_64.c
> >>> +++ b/arch/x86/mm/init_64.c
> >>> @@ -1225,7 +1225,7 @@ static struct kcore_list kcore_vsyscall;
> >>>
> >>> static void __init register_page_bootmem_info(void)
> >>> {
> >>> -#ifdef CONFIG_NUMA
> >>> +#if defined(CONFIG_NUMA) || defined(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP)
> >>> int i;
> >>>
> >>> for_each_online_node(i)
> >>> diff --git a/fs/Kconfig b/fs/Kconfig
> >>> index 976e8b9033c4..e7c4c2a79311 100644
> >>> --- a/fs/Kconfig
> >>> +++ b/fs/Kconfig
> >>> @@ -245,6 +245,24 @@ config HUGETLBFS
> >>> config HUGETLB_PAGE
> >>> def_bool HUGETLBFS
> >>>
> >>> +config HUGETLB_PAGE_FREE_VMEMMAP
> >>> + def_bool HUGETLB_PAGE
> >>
> >> I'm not sure I understand the rationale for providing this help text if
> >> this is def_bool depending on CONFIG_HUGETLB_PAGE. Are you intending that
> >> this is actually configurable and we want to provide guidance to the admin
> >> on when to disable it (which it currently doesn't)? If not, why have the
> >> help text?
> >
> > This is __not__ configurable. Seems like a comment to help others
> > understand this option. Like Randy said.
>
> Yes, it could be written with '#' (or "comment") comment syntax instead of as
> help text.
Got it. I will update in the next version. Thanks.
>
> thanks.
>
> >>
> >>> + depends on X86_64
> >>> + depends on SPARSEMEM_VMEMMAP
> >>> + depends on HAVE_BOOTMEM_INFO_NODE
> >>> + help
> >>> + The option HUGETLB_PAGE_FREE_VMEMMAP allows for the freeing of
> >>> + some vmemmap pages associated with pre-allocated HugeTLB pages.
> >>> + For example, on X86_64 6 vmemmap pages of size 4KB each can be
> >>> + saved for each 2MB HugeTLB page. 4094 vmemmap pages of size 4KB
> >>> + each can be saved for each 1GB HugeTLB page.
> >>> +
> >>> + When a HugeTLB page is allocated or freed, the vmemmap array
> >>> + representing the range associated with the page will need to be
> >>> + remapped. When a page is allocated, vmemmap pages are freed
> >>> + after remapping. When a page is freed, previously discarded
> >>> + vmemmap pages must be allocated before remapping.
> >>> +
> >>> config MEMFD_CREATE
> >>> def_bool TMPFS || HUGETLBFS
> >>>
> >
>
>
> --
> ~Randy
>
Re: [External] Re: [PATCH v13 02/12] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP
On 1/24/21 8:06 PM, Muchun Song wrote:
> On Mon, Jan 25, 2021 at 7:58 AM David Rientjes wrote:
>>
>>
>> On Sun, 17 Jan 2021, Muchun Song wrote:
>>
>>> The HUGETLB_PAGE_FREE_VMEMMAP option is used to enable the freeing
>>> of unnecessary vmemmap associated with HugeTLB pages. The config
>>> option is introduced early so that supporting code can be written
>>> to depend on the option. The initial version of the code only
>>> provides support for x86-64.
>>>
>>> Like other code which frees vmemmap, this config option depends on
>>> HAVE_BOOTMEM_INFO_NODE. The routine register_page_bootmem_info() is
>>> used to register bootmem info. Therefore, make sure
>>> register_page_bootmem_info is enabled if HUGETLB_PAGE_FREE_VMEMMAP
>>> is defined.
>>>
>>> Signed-off-by: Muchun Song
>>> Reviewed-by: Oscar Salvador
>>> Acked-by: Mike Kravetz
>>> ---
>>> arch/x86/mm/init_64.c | 2 +-
>>> fs/Kconfig| 18 ++
>>> 2 files changed, 19 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
>>> index 0a45f062826e..0435bee2e172 100644
>>> --- a/arch/x86/mm/init_64.c
>>> +++ b/arch/x86/mm/init_64.c
>>> @@ -1225,7 +1225,7 @@ static struct kcore_list kcore_vsyscall;
>>>
>>> static void __init register_page_bootmem_info(void)
>>> {
>>> -#ifdef CONFIG_NUMA
>>> +#if defined(CONFIG_NUMA) || defined(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP)
>>> int i;
>>>
>>> for_each_online_node(i)
>>> diff --git a/fs/Kconfig b/fs/Kconfig
>>> index 976e8b9033c4..e7c4c2a79311 100644
>>> --- a/fs/Kconfig
>>> +++ b/fs/Kconfig
>>> @@ -245,6 +245,24 @@ config HUGETLBFS
>>> config HUGETLB_PAGE
>>> def_bool HUGETLBFS
>>>
>>> +config HUGETLB_PAGE_FREE_VMEMMAP
>>> + def_bool HUGETLB_PAGE
>>
>> I'm not sure I understand the rationale for providing this help text if
>> this is def_bool depending on CONFIG_HUGETLB_PAGE. Are you intending that
>> this is actually configurable and we want to provide guidance to the admin
>> on when to disable it (which it currently doesn't)? If not, why have the
>> help text?
>
> This is __not__ configurable. Seems like a comment to help others
> understand this option. Like Randy said.
Yes, it could be written with '#' (or "comment") comment syntax instead of as
help text.
thanks.
>>
>>> + depends on X86_64
>>> + depends on SPARSEMEM_VMEMMAP
>>> + depends on HAVE_BOOTMEM_INFO_NODE
>>> + help
>>> + The option HUGETLB_PAGE_FREE_VMEMMAP allows for the freeing of
>>> + some vmemmap pages associated with pre-allocated HugeTLB pages.
>>> + For example, on X86_64 6 vmemmap pages of size 4KB each can be
>>> + saved for each 2MB HugeTLB page. 4094 vmemmap pages of size 4KB
>>> + each can be saved for each 1GB HugeTLB page.
>>> +
>>> + When a HugeTLB page is allocated or freed, the vmemmap array
>>> + representing the range associated with the page will need to be
>>> + remapped. When a page is allocated, vmemmap pages are freed
>>> + after remapping. When a page is freed, previously discarded
>>> + vmemmap pages must be allocated before remapping.
>>> +
>>> config MEMFD_CREATE
>>> def_bool TMPFS || HUGETLBFS
>>>
>
--
~Randy
Re: [External] Re: [PATCH v13 02/12] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP
On Mon, Jan 25, 2021 at 7:58 AM David Rientjes wrote:
>
>
> On Sun, 17 Jan 2021, Muchun Song wrote:
>
> > The HUGETLB_PAGE_FREE_VMEMMAP option is used to enable the freeing
> > of unnecessary vmemmap associated with HugeTLB pages. The config
> > option is introduced early so that supporting code can be written
> > to depend on the option. The initial version of the code only
> > provides support for x86-64.
> >
> > Like other code which frees vmemmap, this config option depends on
> > HAVE_BOOTMEM_INFO_NODE. The routine register_page_bootmem_info() is
> > used to register bootmem info. Therefore, make sure
> > register_page_bootmem_info is enabled if HUGETLB_PAGE_FREE_VMEMMAP
> > is defined.
> >
> > Signed-off-by: Muchun Song
> > Reviewed-by: Oscar Salvador
> > Acked-by: Mike Kravetz
> > ---
> > arch/x86/mm/init_64.c | 2 +-
> > fs/Kconfig| 18 ++
> > 2 files changed, 19 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> > index 0a45f062826e..0435bee2e172 100644
> > --- a/arch/x86/mm/init_64.c
> > +++ b/arch/x86/mm/init_64.c
> > @@ -1225,7 +1225,7 @@ static struct kcore_list kcore_vsyscall;
> >
> > static void __init register_page_bootmem_info(void)
> > {
> > -#ifdef CONFIG_NUMA
> > +#if defined(CONFIG_NUMA) || defined(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP)
> > int i;
> >
> > for_each_online_node(i)
> > diff --git a/fs/Kconfig b/fs/Kconfig
> > index 976e8b9033c4..e7c4c2a79311 100644
> > --- a/fs/Kconfig
> > +++ b/fs/Kconfig
> > @@ -245,6 +245,24 @@ config HUGETLBFS
> > config HUGETLB_PAGE
> > def_bool HUGETLBFS
> >
> > +config HUGETLB_PAGE_FREE_VMEMMAP
> > + def_bool HUGETLB_PAGE
>
> I'm not sure I understand the rationale for providing this help text if
> this is def_bool depending on CONFIG_HUGETLB_PAGE. Are you intending that
> this is actually configurable and we want to provide guidance to the admin
> on when to disable it (which it currently doesn't)? If not, why have the
> help text?
This is __not__ configurable. Seems like a comment to help others
understand this option. Like Randy said.
Thanks.
>
> > + depends on X86_64
> > + depends on SPARSEMEM_VMEMMAP
> > + depends on HAVE_BOOTMEM_INFO_NODE
> > + help
> > + The option HUGETLB_PAGE_FREE_VMEMMAP allows for the freeing of
> > + some vmemmap pages associated with pre-allocated HugeTLB pages.
> > + For example, on X86_64 6 vmemmap pages of size 4KB each can be
> > + saved for each 2MB HugeTLB page. 4094 vmemmap pages of size 4KB
> > + each can be saved for each 1GB HugeTLB page.
> > +
> > + When a HugeTLB page is allocated or freed, the vmemmap array
> > + representing the range associated with the page will need to be
> > + remapped. When a page is allocated, vmemmap pages are freed
> > + after remapping. When a page is freed, previously discarded
> > + vmemmap pages must be allocated before remapping.
> > +
> > config MEMFD_CREATE
> > def_bool TMPFS || HUGETLBFS
> >
