| Message ID | 1551071039-20192-6-git-send-email-anshuman.khandual@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64/mm: Enable accounting for page table pages | expand |
On Mon, Feb 25, 2019 at 10:33:58AM +0530, Anshuman Khandual wrote: > Page table pages created for user space processes must be accounted against > their memory control groups if initialized. This just introduces a helper > function pgtable_gfp_flags() which returns PGALLOC_GFP for all kernel page > table page allocations but adds __GFP_ACCOUNT for user page table pages. Can't we have pte_alloc_one_kernel() and pte_alloc_one() explicitly pass the GFP flags down to a __pte_alloc_one() helper, and consistently use pte_alloc_one_kernel() for kernel mappings? That would seem less surprising than hiding that detail in another function. Thanks, Mark. > > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > arch/arm64/include/asm/pgalloc.h | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h > index 076764f66fb0..a02a4d1d967d 100644 > --- a/arch/arm64/include/asm/pgalloc.h > +++ b/arch/arm64/include/asm/pgalloc.h > @@ -100,12 +100,24 @@ pte_alloc_one_kernel(struct mm_struct *mm) > return (pte_t *)pte_alloc_one_virt(mm); > } > > +extern struct mm_struct efi_mm; > + > +static inline gfp_t pgtable_gfp_flags(struct mm_struct *mm) > +{ > + if (unlikely((mm == &init_mm) || (mm == &efi_mm))) > + return PGALLOC_GFP; > + else > + return PGALLOC_GFP | __GFP_ACCOUNT; > +} > + > static inline pgtable_t > pte_alloc_one(struct mm_struct *mm) > { > struct page *pte; > + gfp_t gfp; > > - pte = alloc_pages(PGALLOC_GFP, 0); > + gfp = pgtable_gfp_flags(mm); > + pte = alloc_pages(gfp, 0); > if (!pte) > return NULL; > if (!pgtable_page_ctor(pte)) { > -- > 2.20.1 >
On 02/25/2019 04:41 PM, Mark Rutland wrote: > On Mon, Feb 25, 2019 at 10:33:58AM +0530, Anshuman Khandual wrote: >> Page table pages created for user space processes must be accounted against >> their memory control groups if initialized. This just introduces a helper >> function pgtable_gfp_flags() which returns PGALLOC_GFP for all kernel page >> table page allocations but adds __GFP_ACCOUNT for user page table pages. > > Can't we have pte_alloc_one_kernel() and pte_alloc_one() explicitly pass > the GFP flags down to a __pte_alloc_one() helper, and consistently use > pte_alloc_one_kernel() for kernel mappings? > > That would seem less surprising than hiding that detail in another > function. Yes that will work as well. But its better to have this mm_struct based GFP switch which is used in other archs as well to create generic MM helper functions going forward.
On Mon, Feb 25, 2019 at 08:19:53PM +0530, Anshuman Khandual wrote: > > > On 02/25/2019 04:41 PM, Mark Rutland wrote: > > On Mon, Feb 25, 2019 at 10:33:58AM +0530, Anshuman Khandual wrote: > >> Page table pages created for user space processes must be accounted against > >> their memory control groups if initialized. This just introduces a helper > >> function pgtable_gfp_flags() which returns PGALLOC_GFP for all kernel page > >> table page allocations but adds __GFP_ACCOUNT for user page table pages. > > > > Can't we have pte_alloc_one_kernel() and pte_alloc_one() explicitly pass > > the GFP flags down to a __pte_alloc_one() helper, and consistently use > > pte_alloc_one_kernel() for kernel mappings? > > > > That would seem less surprising than hiding that detail in another > > function. > > Yes that will work as well. But its better to have this mm_struct based GFP switch > which is used in other archs as well to create generic MM helper functions going > forward. I don't follow -- if we can make pte_alloc_one() generic, then we can *also* make pte_alloc_one_kernel() generic. Looking at x86, I see: pte_t *pte_alloc_one_kernel(struct mm_struct *mm) { return (pte_t *)__get_free_page(PGALLOC_GFP & ~__GFP_ACCOUNT); } ... which arhitectures do you see which look at the mm struct to decide the flags? Thanks, Mark.
On 02/25/2019 09:05 PM, Mark Rutland wrote: > On Mon, Feb 25, 2019 at 08:19:53PM +0530, Anshuman Khandual wrote: >> >> >> On 02/25/2019 04:41 PM, Mark Rutland wrote: >>> On Mon, Feb 25, 2019 at 10:33:58AM +0530, Anshuman Khandual wrote: >>>> Page table pages created for user space processes must be accounted against >>>> their memory control groups if initialized. This just introduces a helper >>>> function pgtable_gfp_flags() which returns PGALLOC_GFP for all kernel page >>>> table page allocations but adds __GFP_ACCOUNT for user page table pages. >>> >>> Can't we have pte_alloc_one_kernel() and pte_alloc_one() explicitly pass >>> the GFP flags down to a __pte_alloc_one() helper, and consistently use >>> pte_alloc_one_kernel() for kernel mappings? >>> >>> That would seem less surprising than hiding that detail in another >>> function. >> >> Yes that will work as well. But its better to have this mm_struct based GFP switch >> which is used in other archs as well to create generic MM helper functions going >> forward. > > I don't follow -- if we can make pte_alloc_one() generic, then we can > *also* make pte_alloc_one_kernel() generic. Right but when we do mm_struct can be used to decide applicable GFP for the allocation. The way your proposal defers is that it wants to have the GFP flag unique for both pte_alloc_one and pte_alloc_one_kernel without looking into mm_struct which will work as well. > > Looking at x86, I see: > > pte_t *pte_alloc_one_kernel(struct mm_struct *mm) > { > return (pte_t *)__get_free_page(PGALLOC_GFP & ~__GFP_ACCOUNT); > } > > ... which arhitectures do you see which look at the mm struct to decide > the flags? > On powerpc its an explicit helper function arch/powerpc/include/asm/pgalloc.h (pgtable_gfp_flags) On X86 its not an explicit helper function but we can see arch/x86/include/asm/pgalloc.h static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr) { struct page *page; gfp_t gfp = GFP_KERNEL_ACCOUNT | __GFP_ZERO; if (mm == &init_mm) gfp &= ~__GFP_ACCOUNT; page = alloc_pages(gfp, 0); if (!page) return NULL; if (!pgtable_pmd_page_ctor(page)) { __free_pages(page, 0); return NULL; } return (pmd_t *)page_address(page); } static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr) { gfp_t gfp = GFP_KERNEL_ACCOUNT; if (mm == &init_mm) gfp &= ~__GFP_ACCOUNT; return (pud_t *)get_zeroed_page(gfp); } static inline p4d_t *p4d_alloc_one(struct mm_struct *mm, unsigned long addr) { gfp_t gfp = GFP_KERNEL_ACCOUNT; if (mm == &init_mm) gfp &= ~__GFP_ACCOUNT; return (p4d_t *)get_zeroed_page(gfp); } There are some more places on powerpc and x86 where it does the switch. But you are right, pte_alloc_one_kernel() does not go through ctor functions on other archs. But it should and this series changes it. Do you see any concerns in doing so ?
On 02/25/2019 10:33 AM, Anshuman Khandual wrote: > Page table pages created for user space processes must be accounted against > their memory control groups if initialized. This just introduces a helper > function pgtable_gfp_flags() which returns PGALLOC_GFP for all kernel page > table page allocations but adds __GFP_ACCOUNT for user page table pages. > > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > arch/arm64/include/asm/pgalloc.h | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h > index 076764f66fb0..a02a4d1d967d 100644 > --- a/arch/arm64/include/asm/pgalloc.h > +++ b/arch/arm64/include/asm/pgalloc.h > @@ -100,12 +100,24 @@ pte_alloc_one_kernel(struct mm_struct *mm) > return (pte_t *)pte_alloc_one_virt(mm); > } > > +extern struct mm_struct efi_mm; > + > +static inline gfp_t pgtable_gfp_flags(struct mm_struct *mm) > +{ > + if (unlikely((mm == &init_mm) || (mm == &efi_mm))) > + return PGALLOC_GFP; Hello Will, Checking for efi_mm is not necessary here as we just pass init_mm into pte_alloc_one() from pgd_pgtable_alloc() which is used for all runtime allocations for kernel mappings including init_mm and efi_mm. If we really want to differentiate them, the helper pgtable_alloc() has to be changed to include mm_struct. That might be some amount of code churn. Wondering what will be preferred here. - Anshuman
diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h index 076764f66fb0..a02a4d1d967d 100644 --- a/arch/arm64/include/asm/pgalloc.h +++ b/arch/arm64/include/asm/pgalloc.h @@ -100,12 +100,24 @@ pte_alloc_one_kernel(struct mm_struct *mm) return (pte_t *)pte_alloc_one_virt(mm); } +extern struct mm_struct efi_mm; + +static inline gfp_t pgtable_gfp_flags(struct mm_struct *mm) +{ + if (unlikely((mm == &init_mm) || (mm == &efi_mm))) + return PGALLOC_GFP; + else + return PGALLOC_GFP | __GFP_ACCOUNT; +} + static inline pgtable_t pte_alloc_one(struct mm_struct *mm) { struct page *pte; + gfp_t gfp; - pte = alloc_pages(PGALLOC_GFP, 0); + gfp = pgtable_gfp_flags(mm); + pte = alloc_pages(gfp, 0); if (!pte) return NULL; if (!pgtable_page_ctor(pte)) {
Page table pages created for user space processes must be accounted against their memory control groups if initialized. This just introduces a helper function pgtable_gfp_flags() which returns PGALLOC_GFP for all kernel page table page allocations but adds __GFP_ACCOUNT for user page table pages. Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> --- arch/arm64/include/asm/pgalloc.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)