On Thu, Oct 1, 2020 at 8:37 AM Kirill A. Shutemov kirill.shutemov@linux.intel.com wrote:
On Wed, Sep 30, 2020 at 10:21:20PM +0000, Kalesh Singh wrote:
Android needs to move large memory regions for garbage collection. 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.
Signed-off-by: Kalesh Singh kaleshsingh@google.com
arch/Kconfig | 7 + arch/arm64/include/asm/pgtable.h | 1 + mm/mremap.c | 211 ++++++++++++++++++++++++++----- 3 files changed, 189 insertions(+), 30 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig index af14a567b493..5eabaa00bf9b 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -602,6 +602,13 @@ 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
boolhelpArchitectures that select this are able to move page tables at thePUD level. If there are only 3 page table levels, the move effectivelyhappens at the PGD level.config HAVE_MOVE_PMD bool help diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index d5d3fbe73953..8848125e3024 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -415,6 +415,7 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd) #define pfn_pud(pfn,prot) __pud(__phys_to_pud_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
#define set_pmd_at(mm, addr, pmdp, pmd) set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd)) +#define set_pud_at(mm, addr, pudp, pud) set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud))
#define __p4d_to_phys(p4d) __pte_to_phys(p4d_pte(p4d)) #define __phys_to_p4d_val(phys) __phys_to_pte_val(phys)
This doesn't belong to the patch.
Good catch. I'll move this into a separate patch.
diff --git a/mm/mremap.c b/mm/mremap.c index 138abbae4f75..a5a1440bd366 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -249,14 +249,167 @@ 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 pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr) +{
pgd_t *pgd;p4d_t *p4d;pud_t *pud;pgd = pgd_offset(mm, addr);if (pgd_none_or_clear_bad(pgd))return NULL;p4d = p4d_offset(pgd, addr);if (p4d_none_or_clear_bad(p4d))return NULL;pud = pud_offset(p4d, addr);if (pud_none_or_clear_bad(pud))return NULL;return pud;+}
+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;pgd = pgd_offset(mm, addr);p4d = p4d_alloc(mm, pgd, addr);if (!p4d)return NULL;pud = pud_alloc(mm, p4d, addr);if (!pud)return NULL;return 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. Returns 0 if an invalid pgt_entry is specified.
- */
+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;if (entry == NORMAL_PMD || entry == HPAGE_PMD) {mask = PMD_MASK;size = PMD_SIZE;} else if (entry == NORMAL_PUD) {mask = PUD_MASK;size = PUD_SIZE;} elsereturn 0;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);if (entry == NORMAL_PMD)moved = move_normal_pmd(vma, old_addr, new_addr, old_entry, new_entry);else if (entry == NORMAL_PUD)moved = move_normal_pud(vma, old_addr, new_addr, old_entry, new_entry);else if (entry == HPAGE_PMD)moved = move_huge_pmd(vma, old_addr, new_addr, old_entry, new_entry);elseWARN_ON_ONCE(1);BUILD_BUG() should work.
This doesn't get caught at compile time since entry isn't a constant.
And why not use switch() instead of ifs.
I'll move to switch() in the next version. Thanks, Kalesh
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;@@ -269,14 +422,27 @@ 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;+#ifdef CONFIG_HAVE_MOVE_PUD
/** 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 (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;}+#endif
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;@@ -284,18 +450,10 @@ unsigned long move_page_tables(struct vm_area_struct *vma, 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 (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;@@ -305,15 +463,8 @@ unsigned long move_page_tables(struct vm_area_struct *vma, * 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 } -- 2.28.0.709.gb0816b6eb0-goog
-- Kirill A. Shutemov
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