From c49dd340180260c6239e453263a9a244da9a7c85 Mon Sep 17 00:00:00 2001 From: Kalesh Singh Date: Mon, 14 Dec 2020 19:07:30 -0800 Subject: mm: speedup mremap on 1GB or larger regions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Android needs to move large memory regions for garbage collection. The GC requires moving physical pages of multi-gigabyte heap using mremap. During this move, the application threads have to be paused for correctness. It is critical to keep this pause as short as possible to avoid jitters during user interaction. Optimize mremap for >= 1GB-sized regions by moving at the PUD/PGD level if the source and destination addresses are PUD-aligned. For CONFIG_PGTABLE_LEVELS == 3, moving at the PUD level in effect moves PGD entries, since the PUD entry is “folded back” onto the PGD entry. Add HAVE_MOVE_PUD so that architectures where moving at the PUD level isn't supported/tested can turn this off by not selecting the config. Link: https://lkml.kernel.org/r/20201014005320.2233162-4-kaleshsingh@google.com Signed-off-by: Kalesh Singh Acked-by: Kirill A. Shutemov Reported-by: kernel test robot Cc: Aneesh Kumar K.V Cc: Anshuman Khandual Cc: Arnd Bergmann Cc: Borislav Petkov Cc: Brian Geffon Cc: Catalin Marinas Cc: Christian Brauner Cc: Dave Hansen Cc: Frederic Weisbecker Cc: Gavin Shan Cc: Hassan Naveed Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Jia He Cc: John Hubbard Cc: Kees Cook Cc: Krzysztof Kozlowski Cc: Lokesh Gidra Cc: Mark Rutland Cc: Masahiro Yamada Cc: Masami Hiramatsu Cc: Mike Rapoport Cc: Mina Almasry Cc: Minchan Kim Cc: Peter Zijlstra (Intel) Cc: Ralph Campbell Cc: Ram Pai Cc: Sami Tolvanen Cc: Sandipan Das Cc: SeongJae Park Cc: Shuah Khan Cc: Steven Price Cc: Suren Baghdasaryan Cc: Thomas Gleixner Cc: Will Deacon Cc: Zi Yan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/Kconfig | 7 ++ mm/mremap.c | 230 ++++++++++++++++++++++++++++++++++++++++++++++++----------- 2 files changed, 197 insertions(+), 40 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 4f654c149709..54a240b61f56 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -648,6 +648,13 @@ config HAVE_IRQ_TIME_ACCOUNTING Archs need to ensure they use a high enough resolution clock to support irq time accounting and then call enable_sched_clock_irqtime(). +config HAVE_MOVE_PUD + bool + help + Architectures that select this are able to move page tables at the + PUD level. If there are only 3 page table levels, the move effectively + happens at the PGD level. + config HAVE_MOVE_PMD bool help diff --git a/mm/mremap.c b/mm/mremap.c index 138abbae4f75..078f731277b6 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -30,12 +30,11 @@ #include "internal.h" -static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) +static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr) { pgd_t *pgd; p4d_t *p4d; pud_t *pud; - pmd_t *pmd; pgd = pgd_offset(mm, addr); if (pgd_none_or_clear_bad(pgd)) @@ -49,6 +48,18 @@ static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) if (pud_none_or_clear_bad(pud)) return NULL; + return pud; +} + +static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) +{ + pud_t *pud; + pmd_t *pmd; + + pud = get_old_pud(mm, addr); + if (!pud) + return NULL; + pmd = pmd_offset(pud, addr); if (pmd_none(*pmd)) return NULL; @@ -56,19 +67,27 @@ static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) return pmd; } -static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma, +static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr) { pgd_t *pgd; p4d_t *p4d; - pud_t *pud; - pmd_t *pmd; pgd = pgd_offset(mm, addr); p4d = p4d_alloc(mm, pgd, addr); if (!p4d) return NULL; - pud = pud_alloc(mm, p4d, addr); + + return pud_alloc(mm, p4d, addr); +} + +static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long addr) +{ + pud_t *pud; + pmd_t *pmd; + + pud = alloc_new_pud(mm, vma, addr); if (!pud) return NULL; @@ -249,14 +268,148 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr, return true; } +#else +static inline bool move_normal_pmd(struct vm_area_struct *vma, + unsigned long old_addr, unsigned long new_addr, pmd_t *old_pmd, + pmd_t *new_pmd) +{ + return false; +} #endif +#ifdef CONFIG_HAVE_MOVE_PUD +static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr, + unsigned long new_addr, pud_t *old_pud, pud_t *new_pud) +{ + spinlock_t *old_ptl, *new_ptl; + struct mm_struct *mm = vma->vm_mm; + pud_t pud; + + /* + * The destination pud shouldn't be established, free_pgtables() + * should have released it. + */ + if (WARN_ON_ONCE(!pud_none(*new_pud))) + return false; + + /* + * We don't have to worry about the ordering of src and dst + * ptlocks because exclusive mmap_lock prevents deadlock. + */ + old_ptl = pud_lock(vma->vm_mm, old_pud); + new_ptl = pud_lockptr(mm, new_pud); + if (new_ptl != old_ptl) + spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); + + /* Clear the pud */ + pud = *old_pud; + pud_clear(old_pud); + + VM_BUG_ON(!pud_none(*new_pud)); + + /* Set the new pud */ + set_pud_at(mm, new_addr, new_pud, pud); + flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE); + if (new_ptl != old_ptl) + spin_unlock(new_ptl); + spin_unlock(old_ptl); + + return true; +} +#else +static inline bool move_normal_pud(struct vm_area_struct *vma, + unsigned long old_addr, unsigned long new_addr, pud_t *old_pud, + pud_t *new_pud) +{ + return false; +} +#endif + +enum pgt_entry { + NORMAL_PMD, + HPAGE_PMD, + NORMAL_PUD, +}; + +/* + * Returns an extent of the corresponding size for the pgt_entry specified if + * valid. Else returns a smaller extent bounded by the end of the source and + * destination pgt_entry. + */ +static unsigned long get_extent(enum pgt_entry entry, unsigned long old_addr, + unsigned long old_end, unsigned long new_addr) +{ + unsigned long next, extent, mask, size; + + switch (entry) { + case HPAGE_PMD: + case NORMAL_PMD: + mask = PMD_MASK; + size = PMD_SIZE; + break; + case NORMAL_PUD: + mask = PUD_MASK; + size = PUD_SIZE; + break; + default: + BUILD_BUG(); + break; + } + + next = (old_addr + size) & mask; + /* even if next overflowed, extent below will be ok */ + extent = (next > old_end) ? old_end - old_addr : next - old_addr; + next = (new_addr + size) & mask; + if (extent > next - new_addr) + extent = next - new_addr; + return extent; +} + +/* + * Attempts to speedup the move by moving entry at the level corresponding to + * pgt_entry. Returns true if the move was successful, else false. + */ +static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma, + unsigned long old_addr, unsigned long new_addr, + void *old_entry, void *new_entry, bool need_rmap_locks) +{ + bool moved = false; + + /* See comment in move_ptes() */ + if (need_rmap_locks) + take_rmap_locks(vma); + + switch (entry) { + case NORMAL_PMD: + moved = move_normal_pmd(vma, old_addr, new_addr, old_entry, + new_entry); + break; + case NORMAL_PUD: + moved = move_normal_pud(vma, old_addr, new_addr, old_entry, + new_entry); + break; + case HPAGE_PMD: + moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && + move_huge_pmd(vma, old_addr, new_addr, old_entry, + new_entry); + break; + default: + WARN_ON_ONCE(1); + break; + } + + if (need_rmap_locks) + drop_rmap_locks(vma); + + return moved; +} + unsigned long move_page_tables(struct vm_area_struct *vma, unsigned long old_addr, struct vm_area_struct *new_vma, unsigned long new_addr, unsigned long len, bool need_rmap_locks) { - unsigned long extent, next, old_end; + unsigned long extent, old_end; struct mmu_notifier_range range; pmd_t *old_pmd, *new_pmd; @@ -269,53 +422,50 @@ unsigned long move_page_tables(struct vm_area_struct *vma, for (; old_addr < old_end; old_addr += extent, new_addr += extent) { cond_resched(); - next = (old_addr + PMD_SIZE) & PMD_MASK; - /* even if next overflowed, extent below will be ok */ - extent = next - old_addr; - if (extent > old_end - old_addr) - extent = old_end - old_addr; - next = (new_addr + PMD_SIZE) & PMD_MASK; - if (extent > next - new_addr) - extent = next - new_addr; + /* + * If extent is PUD-sized try to speed up the move by moving at the + * PUD level if possible. + */ + extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr); + if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD) && extent == PUD_SIZE) { + pud_t *old_pud, *new_pud; + + old_pud = get_old_pud(vma->vm_mm, old_addr); + if (!old_pud) + continue; + new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr); + if (!new_pud) + break; + if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr, + old_pud, new_pud, need_rmap_locks)) + continue; + } + + extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr); old_pmd = get_old_pmd(vma->vm_mm, old_addr); if (!old_pmd) continue; new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); if (!new_pmd) break; - if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || pmd_devmap(*old_pmd)) { - if (extent == HPAGE_PMD_SIZE) { - bool moved; - /* See comment in move_ptes() */ - if (need_rmap_locks) - take_rmap_locks(vma); - moved = move_huge_pmd(vma, old_addr, new_addr, - old_pmd, new_pmd); - if (need_rmap_locks) - drop_rmap_locks(vma); - if (moved) - continue; - } + if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) || + pmd_devmap(*old_pmd)) { + if (extent == HPAGE_PMD_SIZE && + move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr, + old_pmd, new_pmd, need_rmap_locks)) + continue; split_huge_pmd(vma, old_pmd, old_addr); if (pmd_trans_unstable(old_pmd)) continue; - } else if (extent == PMD_SIZE) { -#ifdef CONFIG_HAVE_MOVE_PMD + } else if (IS_ENABLED(CONFIG_HAVE_MOVE_PMD) && + extent == PMD_SIZE) { /* * If the extent is PMD-sized, try to speed the move by * moving at the PMD level if possible. */ - bool moved; - - if (need_rmap_locks) - take_rmap_locks(vma); - moved = move_normal_pmd(vma, old_addr, new_addr, - old_pmd, new_pmd); - if (need_rmap_locks) - drop_rmap_locks(vma); - if (moved) + if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr, + old_pmd, new_pmd, need_rmap_locks)) continue; -#endif } if (pte_alloc(new_vma->vm_mm, new_pmd)) -- cgit v1.2.3