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Message-Id: <972208b7-5c05-cc05-efbf-0d48bff4cf77@linux.ibm.com>
Date: Thu, 14 Mar 2019 18:47:35 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
To: Alexandre Ghiti <alex@...ti.fr>,
Andrew Morton <akpm@...ux-foundation.org>,
Vlastimil Babka <vbabka@...e.cz>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Yoshinori Sato <ysato@...rs.sourceforge.jp>,
Rich Felker <dalias@...c.org>,
"David S . Miller" <davem@...emloft.net>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
Dave Hansen <dave.hansen@...ux.intel.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Mike Kravetz <mike.kravetz@...cle.com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
linux-mm@...ck.org
Subject: Re: [PATCH v6 4/4] hugetlb: allow to free gigantic pages regardless
of the configuration
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@...ti.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@...ti.fr>
>>> Acked-by: David S. Miller <davem@...emloft.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.
> 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.
> +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.
> +
> 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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