Re: [PATCH 3/3] mm: hugetlb: add hugetlb_free_vmemmap sysctl

[Muchun Song]

On Mon, Feb 28, 2022 at 10:42 PM Luis Chamberlain <mcgrof@xxxxxxxxxx> wrote:
>
> On Mon, Feb 28, 2022 at 03:10:22PM +0800, Muchun Song wrote:
> > We must add "hugetlb_free_vmemmap=on" to boot cmdline and reboot the
> > server to enable the feature of freeing vmemmap pages of HugeTLB
> > pages. Rebooting usually taske a long time. Add a sysctl to enable
> > the feature at runtime and do not need to reboot.
> >
> > Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> > ---
> >  Documentation/admin-guide/sysctl/vm.rst | 13 +++++++++++++
> >  include/linux/hugetlb.h                 |  5 +++++
> >  include/linux/memory_hotplug.h          |  1 +
> >  kernel/sysctl.c                         | 11 +++++++++++
>
> kernel/sysctl.c is a hot mess with tons of knobs from all over the
> place. And so we've been moving these to their own place. For instance
> all the filesystem knobs are now properly in fs/. So Adding new ones
> to the file is undesirable. If this is going to be added, please add
> it somewhere in mm / hugetlb code.
>

I also have realized this when reading another patch [1]. I will
move this into its hugetlb related code.  Anyway, thanks for
your suggestion.

[1] https://lore.kernel.org/linux-fsdevel/20220220060626.15885-1-tangmeng@xxxxxxxxxxxxx/