From a53efe5ff88d0283bae8a2c2fa066d0fff31dc91 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Fri, 26 Oct 2012 17:17:44 +0200 Subject: sched/mm: call finish_arch_post_lock_switch in idle_task_exit and use_mm The finish_arch_post_lock_switch is called at the end of the task switch after all locks have been released. In concept it is paired with the switch_mm function, but the current code only does the call in finish_task_switch. Add the call to idle_task_exit and use_mm. One use case for the additional calls is s390 which will use finish_arch_post_lock_switch to wait for the completion of TLB flush operations. Signed-off-by: Martin Schwidefsky --- mm/mmu_context.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'mm') diff --git a/mm/mmu_context.c b/mm/mmu_context.c index 8a8cd0265e52..f802c2d216a7 100644 --- a/mm/mmu_context.c +++ b/mm/mmu_context.c @@ -31,6 +31,9 @@ void use_mm(struct mm_struct *mm) tsk->mm = mm; switch_mm(active_mm, mm, tsk); task_unlock(tsk); +#ifdef finish_arch_post_lock_switch + finish_arch_post_lock_switch(); +#endif if (active_mm != mm) mmdrop(active_mm); -- cgit v1.2.3 From 45961722f8e30ceab9d135b1ddc0947d53aef7c3 Mon Sep 17 00:00:00 2001 From: Konstantin Weitz Date: Wed, 17 Apr 2013 13:59:32 +0200 Subject: mm: add support for discard of unused ptes In a virtualized environment and given an appropriate interface the guest can mark pages as unused while they are free (for the s390 implementation see git commit 45e576b1c3d00206 "guest page hinting light"). For the host the unused state is a property of the pte. This patch adds the primitive 'pte_unused' and code to the host swap out handler so that pages marked as unused by all mappers are not swapped out but discarded instead, thus saving one IO for swap out and potentially another one for swap in. [ Martin Schwidefsky: patch reordering and simplification ] Signed-off-by: Konstantin Weitz Signed-off-by: Martin Schwidefsky --- include/asm-generic/pgtable.h | 13 +++++++++++++ mm/rmap.c | 10 ++++++++++ 2 files changed, 23 insertions(+) (limited to 'mm') diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index 34c7bdc06014..1ec08c198b66 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -193,6 +193,19 @@ static inline int pte_same(pte_t pte_a, pte_t pte_b) } #endif +#ifndef __HAVE_ARCH_PTE_UNUSED +/* + * Some architectures provide facilities to virtualization guests + * so that they can flag allocated pages as unused. This allows the + * host to transparently reclaim unused pages. This function returns + * whether the pte's page is unused. + */ +static inline int pte_unused(pte_t pte) +{ + return 0; +} +#endif + #ifndef __HAVE_ARCH_PMD_SAME #ifdef CONFIG_TRANSPARENT_HUGEPAGE static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b) diff --git a/mm/rmap.c b/mm/rmap.c index d9d42316a99a..9056a1f00b87 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1165,6 +1165,16 @@ int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, } set_pte_at(mm, address, pte, swp_entry_to_pte(make_hwpoison_entry(page))); + } else if (pte_unused(pteval)) { + /* + * The guest indicated that the page content is of no + * interest anymore. Simply discard the pte, vmscan + * will take care of the rest. + */ + if (PageAnon(page)) + dec_mm_counter(mm, MM_ANONPAGES); + else + dec_mm_counter(mm, MM_FILEPAGES); } else if (PageAnon(page)) { swp_entry_t entry = { .val = page_private(page) }; pte_t swp_pte; -- cgit v1.2.3