Re: [PATCH] mm/hugetlb: remove gigantic page support for HIGHMEM
- Date: Wed, 11 Jul 2018 14:36:16 -0700
- From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
- Subject: Re: [PATCH] mm/hugetlb: remove gigantic page support for HIGHMEM
On 07/11/2018 01:57 PM, Davidlohr Bueso wrote:
> On Wed, 11 Jul 2018, Mike Kravetz wrote:
>> This reverts commit ee8f248d266e ("hugetlb: add phys addr to struct
>> At one time powerpc used this field and supporting code. However that
>> was removed with commit 79cc38ded1e1 ("powerpc/mm/hugetlb: Add support
>> for reserving gigantic huge pages via kernel command line").
>> There are no users of this field and supporting code, so remove it.
> Considering the title, don't you wanna also get rid of try_to_free_low()
> and something like the following, which I'm sure can be done fancier, and
> perhaps also thp?
Not really. The intention is to only remove gigantic huge page support for
HIGHMEN systems. Non-gigantic huge pages on HIGHMEN systems should still
work/be supported. So, we do not want to make the config change or get
rid of try_to_free_low().
Actually, I simply wanted to revert the specific patch which enabled gigantic
huge pages on HIGHMEM systems. I did see that check in try_to_free_low(),
and considered for a minute turning that into a VM_BUG or WARN, but decided
to leave it as is.
Do you think the title should be changed to simply 'revert commit
> diff --git a/fs/Kconfig b/fs/Kconfig
> index ac474a61be37..849da70e35d6 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -192,8 +192,8 @@ config TMPFS_XATTR
> config HUGETLBFS
> bool "HugeTLB file system support"
> - depends on X86 || IA64 || SPARC64 || (S390 && 64BIT) || \
> - SYS_SUPPORTS_HUGETLBFS || BROKEN
> + depends on !HIGHMEM && (X86 || IA64 || SPARC64 || (S390 && 64BIT) || \
> + SYS_SUPPORTS_HUGETLBFS || BROKEN)
> hugetlbfs is a filesystem backing for HugeTLB pages, based on
> ramfs. For architectures that support it, say Y here and read