[PATCH v6 4/4] hugetlb: allow to free gigantic pages regardless of the configuration
Alexandre Ghiti
alex at ghiti.fr
Fri Mar 15 00:52:41 AEDT 2019
On 03/14/2019 02:17 PM, Aneesh Kumar K.V wrote:
> On 3/14/19 5:13 PM, Alexandre Ghiti wrote:
>> On 03/14/2019 06:52 AM, Aneesh Kumar K.V wrote:
>>> Alexandre Ghiti <alex at ghiti.fr> writes:
>>>
>>>> On systems without CONTIG_ALLOC activated but that support gigantic
>>>> pages,
>>>> boottime reserved gigantic pages can not be freed at all. This patch
>>>> simply enables the possibility to hand back those pages to memory
>>>> allocator.
>>>>
>>>> Signed-off-by: Alexandre Ghiti <alex at ghiti.fr>
>>>> Acked-by: David S. Miller <davem at davemloft.net> [sparc]
>>>> ---
>>>> arch/arm64/Kconfig | 2 +-
>>>> arch/arm64/include/asm/hugetlb.h | 4 --
>>>> arch/powerpc/include/asm/book3s/64/hugetlb.h | 7 ---
>>>> arch/powerpc/platforms/Kconfig.cputype | 2 +-
>>>> arch/s390/Kconfig | 2 +-
>>>> arch/s390/include/asm/hugetlb.h | 3 --
>>>> arch/sh/Kconfig | 2 +-
>>>> arch/sparc/Kconfig | 2 +-
>>>> arch/x86/Kconfig | 2 +-
>>>> arch/x86/include/asm/hugetlb.h | 4 --
>>>> include/linux/gfp.h | 2 +-
>>>> mm/hugetlb.c | 57
>>>> ++++++++++++--------
>>>> mm/page_alloc.c | 4 +-
>>>> 13 files changed, 44 insertions(+), 49 deletions(-)
>>>>
>>>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>>>> index 091a513b93e9..af687eff884a 100644
>>>> --- a/arch/arm64/Kconfig
>>>> +++ b/arch/arm64/Kconfig
>>>> @@ -18,7 +18,7 @@ config ARM64
>>>> select ARCH_HAS_FAST_MULTIPLIER
>>>> select ARCH_HAS_FORTIFY_SOURCE
>>>> select ARCH_HAS_GCOV_PROFILE_ALL
>>>> - select ARCH_HAS_GIGANTIC_PAGE if CONTIG_ALLOC
>>>> + select ARCH_HAS_GIGANTIC_PAGE
>>>> select ARCH_HAS_KCOV
>>>> select ARCH_HAS_MEMBARRIER_SYNC_CORE
>>>> select ARCH_HAS_PTE_SPECIAL
>>>> diff --git a/arch/arm64/include/asm/hugetlb.h
>>>> b/arch/arm64/include/asm/hugetlb.h
>>>> index fb6609875455..59893e766824 100644
>>>> --- a/arch/arm64/include/asm/hugetlb.h
>>>> +++ b/arch/arm64/include/asm/hugetlb.h
>>>> @@ -65,8 +65,4 @@ extern void set_huge_swap_pte_at(struct mm_struct
>>>> *mm, unsigned long addr,
>>>> #include <asm-generic/hugetlb.h>
>>>> -#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
>>>> -static inline bool gigantic_page_supported(void) { return true; }
>>>> -#endif
>>>> -
>>>> #endif /* __ASM_HUGETLB_H */
>>>> diff --git a/arch/powerpc/include/asm/book3s/64/hugetlb.h
>>>> b/arch/powerpc/include/asm/book3s/64/hugetlb.h
>>>> index 5b0177733994..d04a0bcc2f1c 100644
>>>> --- a/arch/powerpc/include/asm/book3s/64/hugetlb.h
>>>> +++ b/arch/powerpc/include/asm/book3s/64/hugetlb.h
>>>> @@ -32,13 +32,6 @@ static inline int hstate_get_psize(struct hstate
>>>> *hstate)
>>>> }
>>>> }
>>>> -#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
>>>> -static inline bool gigantic_page_supported(void)
>>>> -{
>>>> - return true;
>>>> -}
>>>> -#endif
>>>> -
>>>> /* hugepd entry valid bit */
>>>> #define HUGEPD_VAL_BITS (0x8000000000000000UL)
>>> As explained in https://patchwork.ozlabs.org/patch/1047003/
>>> architectures like ppc64 have a hypervisor assisted mechanism to
>>> indicate
>>> where to find gigantic huge pages(16G pages). At this point, we
>>> don't use this
>>> reserved pages for anything other than hugetlb backing and hence there
>>> is no runtime free of this pages needed ( Also we don't do
>>> runtime allocation of them).
>>>
>>> I guess you can still achieve what you want to do in this patch by
>>> keeping gigantic_page_supported()?
>>>
>>> NOTE: We should rename gigantic_page_supported to be more specific to
>>> support for runtime_alloc/free of gigantic pages
>>>
>>> -aneesh
>>>
>> Thanks for noticing Aneesh.
>>
>> I can't find a better solution than bringing back
>> gigantic_page_supported check,
>> since it is must be done at runtime in your case.
>> I'm not sure of one thing though: you say that freeing boottime
>> gigantic pages
>> is not needed, but is it forbidden ? Just to know where the check and
>> what its
>> new name should be.
You did not answer this question: is freeing boottime gigantic pages
"forbidden" or just
not needed ?
>> Is something like that (on top of this series) ok for you (and
>> everyone else) before
>> I send a v7:
>>
>> diff --git a/arch/powerpc/include/asm/book3s/64/hugetlb.h
>> b/arch/powerpc/include/asm/book3s/64/hugetlb.h
>> index d04a0bc..d121559 100644
>> --- a/arch/powerpc/include/asm/book3s/64/hugetlb.h
>> +++ b/arch/powerpc/include/asm/book3s/64/hugetlb.h
>> @@ -35,4 +35,20 @@ static inline int hstate_get_psize(struct hstate
>> *hstate)
>> /* hugepd entry valid bit */
>> #define HUGEPD_VAL_BITS (0x8000000000000000UL)
>>
>> +#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
>> +#define __HAVE_ARCH_GIGANTIC_PAGE_SUPPORTED
>> +static inline bool gigantic_page_supported(void)
>> +{
>> + /*
>> + * We used gigantic page reservation with hypervisor assist
>> in some case.
>> + * We cannot use runtime allocation of gigantic pages in
>> those platforms
>> + * This is hash translation mode LPARs.
>> + */
>> + if (firmware_has_feature(FW_FEATURE_LPAR) && !radix_enabled())
>> + return false;
>> +
>> + return true;
>> +}
>> +#endif
>> +
>> #endif
>> diff --git a/include/asm-generic/hugetlb.h
>> b/include/asm-generic/hugetlb.h
>> index 71d7b77..7d12e73 100644
>> --- a/include/asm-generic/hugetlb.h
>> +++ b/include/asm-generic/hugetlb.h
>> @@ -126,4 +126,18 @@ static inline pte_t huge_ptep_get(pte_t *ptep)
>> }
>> #endif
>>
>> +#ifndef __HAVE_ARCH_GIGANTIC_PAGE_SUPPORTED
>> +#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
>
>
> The pattern i like is
>
> #ifndef gigantic_page_supported
> #define gigantic_page_supported gigantic_page_supported
>
> static inline bool gigantic_page_supported(void)
> {
> return true;
> }
>
> #endif
>
> instead of _HAVE_ARCH_GIGANTIC_PAGE_SUPPORTED.
>
I see, that avoids a new define. However, it is not consistent with the
rest of function definitions
in generic hugetlb.h. What do you think ? Should I follow the same
format ? Or use yours ?
>
>> +static inline bool gigantic_page_supported(void)
>> +{
>> + return true;
>> +}
>> +#else
>> +static inline bool gigantic_page_supported(void)
>> +{
>> + return false;
>> +}
>> +#endif /* CONFIG_ARCH_HAS_GIGANTIC_PAGE */
>> +#endif /* __HAVE_ARCH_GIGANTIC_PAGE_SUPPORTED */
>> +
>> #endif /* _ASM_GENERIC_HUGETLB_H */
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index 9fc96ef..cfbbafe 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -2425,6 +2425,11 @@ static ssize_t
>> __nr_hugepages_store_common(bool obey_mempolicy,
>> int err;
>> NODEMASK_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL |
>> __GFP_NORETRY);
>>
>> + if (hstate_is_gigantic(h) && !gigantic_page_supported()) {
>> + err = -EINVAL;
>> + goto out;
>> + }
>
>
> you should restore other users of gigantic_page_supported() not just
> this. That will just make your earlier patch as removing
> gigantic_page_supported from every architecture other than ppc64 and
> have a generic version as above.
>
>
I'll restore the check in update_and_free_page too depending on your
answer to the above question,
since adding this check back would not allow to free boottime gigantic
pages.
>> +
>> if (nid == NUMA_NO_NODE) {
>> /*
>> * global hstate attribute
>> @@ -2446,6 +2451,7 @@ static ssize_t __nr_hugepages_store_common(bool
>> obey_mempolicy,
>>
>> err = set_max_huge_pages(h, count, nodes_allowed);
>>
>> +out:
>> if (nodes_allowed != &node_states[N_MEMORY])
>> NODEMASK_FREE(nodes_allowed);
>>
>>
>>
>>
>
> -aneesh.
>
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