diff options
| author | Will Deacon <will.deacon@arm.com> | 2015-10-06 18:46:30 +0100 |
|---|---|---|
| committer | Amit Pundir <amit.pundir@linaro.org> | 2016-12-05 12:24:04 +0530 |
| commit | a5b32bef7a81beba00527d54c8d380db526b7f30 (patch) | |
| tree | 60717e779812d04e2d0a3e62c854bd49a7e8962a /arch | |
| parent | b3d5e88c1a55854400381b7960701527d1dcc057 (diff) | |
UPSTREAM: arm64: mm: remove dsb from update_mmu_cache
update_mmu_cache() consists of a dsb(ishst) instruction so that new user
mappings are guaranteed to be visible to the page table walker on
exception return.
In reality this can be a very expensive operation which is rarely needed.
Removing this barrier shows a modest improvement in hackbench scores and
, in the worst case, we re-take the user fault and establish that there
was nothing to do.
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Bug: 31432001
Change-Id: Ifb71e6b0154dacdd6ec380b897e962ffd0eb5ad9
(cherry picked from commit 120798d2e7d1ac87365fe5ea91b074bb42ca1eff)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/include/asm/pgtable.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index e40a643e5c52..09b45f4ef3ce 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -523,10 +523,10 @@ static inline void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep) { /* - * set_pte() does not have a DSB for user mappings, so make sure that - * the page table write is visible. + * We don't do anything here, so there's a very small chance of + * us retaking a user fault which we just fixed up. The alternative + * is doing a dsb(ishst), but that penalises the fastpath. */ - dsb(ishst); } #define update_mmu_cache_pmd(vma, address, pmd) do { } while (0) |