[+Mark]
On Thu, Feb 14, 2019 at 02:16:42PM -0700, Yu Zhao wrote:
> Switch from per mm_struct to per pmd page table lock by enabling
> ARCH_ENABLE_SPLIT_PMD_PTLOCK. This provides better granularity for
> large system.
>
> I'm not sure if there is contention on mm->page_table_lock. Given
> the option comes at no cost (apart from initializing more spin
> locks), why not enable it now.
>
> Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
> ---
> arch/arm64/Kconfig | 3 +++
> arch/arm64/include/asm/pgalloc.h | 12 +++++++++++-
> arch/arm64/include/asm/tlb.h | 5 ++++-
> 3 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index a4168d366127..104325a1ffc3 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -872,6 +872,9 @@ config ARCH_WANT_HUGE_PMD_SHARE
> config ARCH_HAS_CACHE_LINE_SIZE
> def_bool y
>
> +config ARCH_ENABLE_SPLIT_PMD_PTLOCK
> + def_bool y
> +
> config SECCOMP
> bool "Enable seccomp to safely compute untrusted bytecode"
> ---help---
> diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h
> index 52fa47c73bf0..dabba4b2c61f 100644
> --- a/arch/arm64/include/asm/pgalloc.h
> +++ b/arch/arm64/include/asm/pgalloc.h
> @@ -33,12 +33,22 @@
>
> static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr)
> {
> - return (pmd_t *)__get_free_page(PGALLOC_GFP);
> + struct page *page;
> +
> + page = alloc_page(PGALLOC_GFP);
> + if (!page)
> + return NULL;
> + if (!pgtable_pmd_page_ctor(page)) {
> + __free_page(page);
> + return NULL;
> + }
> + return page_address(page);
I'm a bit worried as to how this interacts with the page-table code in
arch/arm64/mm/mmu.c when pgd_pgtable_alloc is used as the allocator. It
looks like that currently always calls pgtable_page_ctor(), regardless of
level. Do we now need a separate allocator function for the PMD level?
Will
