Re: [PATCH v4 4/4] mm: introduce MADV_PAGEOUT

Michal Hocko
2019-07-12T07:19:57Z

On Fri 12-07-19 14:18:28, Minchan Kim wrote:
[...]
> >From 41592f23e876ec21e49dc3c76dc89538e2bb16be Mon Sep 17 00:00:00 2001
> From: Minchan Kim <minchan@kernel.org>
> Date: Fri, 12 Jul 2019 14:05:36 +0900
> Subject: [PATCH] mm: factor out common parts between MADV_COLD and
> MADV_PAGEOUT
>
> There are many common parts between MADV_COLD and MADV_PAGEOUT.
> This patch factor them out to save code duplication.

This looks better indeed. I still hope that this can get improved even
further but let's do that in a follow up patch.

> Signed-off-by: Minchan Kim <minchan@kernel.org>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> mm/madvise.c | 201 +++++++++++++--------------------------------------
> 1 file changed, 52 insertions(+), 149 deletions(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index bc2f0138982e..3d3d14517cc8 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -30,6 +30,11 @@
>
> #include "internal.h"
>
> +struct madvise_walk_private {
> + struct mmu_gather *tlb;
> + bool pageout;
> +};
> +
> /*
> * Any behaviour which results in changes to the vma->vm_flags needs to
> * take mmap_sem for writing. Others, which simply traverse vmas, need
> @@ -310,16 +315,23 @@ static long madvise_willneed(struct vm_area_struct *vma,
> return 0;
> }
>
> -static int madvise_cold_pte_range(pmd_t *pmd, unsigned long addr,
> - unsigned long end, struct mm_walk *walk)
> +static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
> + unsigned long addr, unsigned long end,
> + struct mm_walk *walk)
> {
> - struct mmu_gather *tlb = walk->private;
> + struct madvise_walk_private *private = walk->private;
> + struct mmu_gather *tlb = private->tlb;
> + bool pageout = private->pageout;
> struct mm_struct *mm = tlb->mm;
> struct vm_area_struct *vma = walk->vma;
> pte_t *orig_pte, *pte, ptent;
> spinlock_t *ptl;
> - struct page *page;
> unsigned long next;
> + struct page *page = NULL;
> + LIST_HEAD(page_list);
> +
> + if (fatal_signal_pending(current))
> + return -EINTR;
>
> next = pmd_addr_end(addr, end);
> if (pmd_trans_huge(*pmd)) {
> @@ -358,6 +370,12 @@ static int madvise_cold_pte_range(pmd_t *pmd, unsigned long addr,
> return 0;
> }
>
> + if (pageout) {
> + if (isolate_lru_page(page))
> + goto huge_unlock;
> + list_add(&page->lru, &page_list);
> + }
> +
> if (pmd_young(orig_pmd)) {
> pmdp_invalidate(vma, addr, pmd);
> orig_pmd = pmd_mkold(orig_pmd);
> @@ -366,10 +384,14 @@ static int madvise_cold_pte_range(pmd_t *pmd, unsigned long addr,
> tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
> }
>
> + ClearPageReferenced(page);
> test_and_clear_page_young(page);
> - deactivate_page(page);
> huge_unlock:
> spin_unlock(ptl);
> + if (pageout)
> + reclaim_pages(&page_list);
> + else
> + deactivate_page(page);
> return 0;
> }
>
> @@ -423,6 +445,12 @@ static int madvise_cold_pte_range(pmd_t *pmd, unsigned long addr,
>
> VM_BUG_ON_PAGE(PageTransCompound(page), page);
>
> + if (pageout) {
> + if (isolate_lru_page(page))
> + continue;
> + list_add(&page->lru, &page_list);
> + }
> +
> if (pte_young(ptent)) {
> ptent = ptep_get_and_clear_full(mm, addr, pte,
> tlb->fullmm);
> @@ -437,12 +465,16 @@ static int madvise_cold_pte_range(pmd_t *pmd, unsigned long addr,
> * As a side effect, it makes confuse idle-page tracking
> * because they will miss recent referenced history.
> */
> + ClearPageReferenced(page);
> test_and_clear_page_young(page);
> - deactivate_page(page);
> + if (!pageout)
> + deactivate_page(page);
> }
>
> arch_enter_lazy_mmu_mode();
> pte_unmap_unlock(orig_pte, ptl);
> + if (pageout)
> + reclaim_pages(&page_list);
> cond_resched();
>
> return 0;
> @@ -452,10 +484,15 @@ static void madvise_cold_page_range(struct mmu_gather *tlb,
> struct vm_area_struct *vma,
> unsigned long addr, unsigned long end)
> {
> + struct madvise_walk_private walk_private = {
> + .tlb = tlb,
> + .pageout = false,
> + };
> +
> struct mm_walk cold_walk = {
> - .pmd_entry = madvise_cold_pte_range,
> + .pmd_entry = madvise_cold_or_pageout_pte_range,
> .mm = vma->vm_mm,
> - .private = tlb,
> + .private = &walk_private,
> };
>
> tlb_start_vma(tlb, vma);
> @@ -482,153 +519,19 @@ static long madvise_cold(struct vm_area_struct *vma,
> return 0;
> }
>
> -static int madvise_pageout_pte_range(pmd_t *pmd, unsigned long addr,
> - unsigned long end, struct mm_walk *walk)
> -{
> - struct mmu_gather *tlb = walk->private;
> - struct mm_struct *mm = tlb->mm;
> - struct vm_area_struct *vma = walk->vma;
> - pte_t *orig_pte, *pte, ptent;
> - spinlock_t *ptl;
> - LIST_HEAD(page_list);
> - struct page *page;
> - unsigned long next;
> -
> - if (fatal_signal_pending(current))
> - return -EINTR;
> -
> - next = pmd_addr_end(addr, end);
> - if (pmd_trans_huge(*pmd)) {
> - pmd_t orig_pmd;
> -
> - tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
> - ptl = pmd_trans_huge_lock(pmd, vma);
> - if (!ptl)
> - return 0;
> -
> - orig_pmd = *pmd;
> - if (is_huge_zero_pmd(orig_pmd))
> - goto huge_unlock;
> -
> - if (unlikely(!pmd_present(orig_pmd))) {
> - VM_BUG_ON(thp_migration_supported() &&
> - !is_pmd_migration_entry(orig_pmd));
> - goto huge_unlock;
> - }
> -
> - page = pmd_page(orig_pmd);
> - if (next - addr != HPAGE_PMD_SIZE) {
> - int err;
> -
> - if (page_mapcount(page) != 1)
> - goto huge_unlock;
> - get_page(page);
> - spin_unlock(ptl);
> - lock_page(page);
> - err = split_huge_page(page);
> - unlock_page(page);
> - put_page(page);
> - if (!err)
> - goto regular_page;
> - return 0;
> - }
> -
> - if (isolate_lru_page(page))
> - goto huge_unlock;
> -
> - if (pmd_young(orig_pmd)) {
> - pmdp_invalidate(vma, addr, pmd);
> - orig_pmd = pmd_mkold(orig_pmd);
> -
> - set_pmd_at(mm, addr, pmd, orig_pmd);
> - tlb_remove_tlb_entry(tlb, pmd, addr);
> - }
> -
> - ClearPageReferenced(page);
> - test_and_clear_page_young(page);
> - list_add(&page->lru, &page_list);
> -huge_unlock:
> - spin_unlock(ptl);
> - reclaim_pages(&page_list);
> - return 0;
> - }
> -
> - if (pmd_trans_unstable(pmd))
> - return 0;
> -regular_page:
> - tlb_change_page_size(tlb, PAGE_SIZE);
> - orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
> - flush_tlb_batched_pending(mm);
> - arch_enter_lazy_mmu_mode();
> - for (; addr < end; pte++, addr += PAGE_SIZE) {
> - ptent = *pte;
> - if (!pte_present(ptent))
> - continue;
> -
> - page = vm_normal_page(vma, addr, ptent);
> - if (!page)
> - continue;
> -
> - /*
> - * creating a THP page is expensive so split it only if we
> - * are sure it's worth. Split it if we are only owner.
> - */
> - if (PageTransCompound(page)) {
> - if (page_mapcount(page) != 1)
> - break;
> - get_page(page);
> - if (!trylock_page(page)) {
> - put_page(page);
> - break;
> - }
> - pte_unmap_unlock(orig_pte, ptl);
> - if (split_huge_page(page)) {
> - unlock_page(page);
> - put_page(page);
> - pte_offset_map_lock(mm, pmd, addr, &ptl);
> - break;
> - }
> - unlock_page(page);
> - put_page(page);
> - pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
> - pte--;
> - addr -= PAGE_SIZE;
> - continue;
> - }
> -
> - VM_BUG_ON_PAGE(PageTransCompound(page), page);
> -
> - if (isolate_lru_page(page))
> - continue;
> -
> - if (pte_young(ptent)) {
> - ptent = ptep_get_and_clear_full(mm, addr, pte,
> - tlb->fullmm);
> - ptent = pte_mkold(ptent);
> - set_pte_at(mm, addr, pte, ptent);
> - tlb_remove_tlb_entry(tlb, pte, addr);
> - }
> - ClearPageReferenced(page);
> - test_and_clear_page_young(page);
> - list_add(&page->lru, &page_list);
> - }
> -
> - arch_leave_lazy_mmu_mode();
> - pte_unmap_unlock(orig_pte, ptl);
> - reclaim_pages(&page_list);
> - cond_resched();
> -
> - return 0;
> -}
> -
> static void madvise_pageout_page_range(struct mmu_gather *tlb,
> struct vm_area_struct *vma,
> unsigned long addr, unsigned long end)
> {
> + struct madvise_walk_private walk_private = {
> + .pageout = true,
> + .tlb = tlb,
> + };
> +
> struct mm_walk pageout_walk = {
> - .pmd_entry = madvise_pageout_pte_range,
> + .pmd_entry = madvise_cold_or_pageout_pte_range,
> .mm = vma->vm_mm,
> - .private = tlb,
> + .private = &walk_private,
> };
>
> tlb_start_vma(tlb, vma);
> --
> 2.22.0.410.gd8fdbe21b5-goog

--
Michal Hocko
SUSE Labs