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Date: Tue, 13 Nov 2012 13:48:35 -0500
From: Johannes Weiner <hannes@...xchg.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Paul Turner <pjt@...gle.com>,
Lee Schermerhorn <Lee.Schermerhorn@...com>,
Christoph Lameter <cl@...ux.com>,
Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Andrea Arcangeli <aarcange@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Thomas Gleixner <tglx@...utronix.de>,
Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH 21/31] sched, numa, mm: Implement THP migration
[Put Hugh back on CC]
What happened to Hugh's fixes to the LRU handling? I believe it was
racy beyond affecting memcg, it's just that memcg code had a BUG_ON in
the right place to point it out.
On Tue, Nov 13, 2012 at 06:13:44PM +0100, Ingo Molnar wrote:
> From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>
> Add THP migration for the NUMA working set scanning fault case.
>
> It uses the page lock to serialize. No migration pte dance is
> necessary because the pte is already unmapped when we decide
> to migrate.
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Link: http://lkml.kernel.org/n/tip-yv9vbiz2s455zxq1ffzx3fye@git.kernel.org
> [ Significant fixes and changelog. ]
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> ---
> mm/huge_memory.c | 131 +++++++++++++++++++++++++++++++++++++++++++------------
> mm/migrate.c | 2 +-
> 2 files changed, 103 insertions(+), 30 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index c4c0a57..931caf4 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -742,12 +742,13 @@ void do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
> unsigned int flags, pmd_t entry)
> {
> unsigned long haddr = address & HPAGE_PMD_MASK;
> + struct page *new_page = NULL;
> struct page *page = NULL;
> - int node;
> + int node, lru;
>
> spin_lock(&mm->page_table_lock);
> if (unlikely(!pmd_same(*pmd, entry)))
> - goto out_unlock;
> + goto unlock;
>
> if (unlikely(pmd_trans_splitting(entry))) {
> spin_unlock(&mm->page_table_lock);
> @@ -755,45 +756,117 @@ void do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
> return;
> }
>
> -#ifdef CONFIG_NUMA
> page = pmd_page(entry);
> - VM_BUG_ON(!PageCompound(page) || !PageHead(page));
> + if (page) {
> + VM_BUG_ON(!PageCompound(page) || !PageHead(page));
>
> - get_page(page);
> - spin_unlock(&mm->page_table_lock);
> + get_page(page);
> + node = mpol_misplaced(page, vma, haddr);
> + if (node != -1)
> + goto migrate;
> + }
>
> - /*
> - * XXX should we serialize against split_huge_page ?
> - */
> +fixup:
> + /* change back to regular protection */
> + entry = pmd_modify(entry, vma->vm_page_prot);
> + set_pmd_at(mm, haddr, pmd, entry);
> + update_mmu_cache_pmd(vma, address, entry);
>
> - node = mpol_misplaced(page, vma, haddr);
> - if (node == -1)
> - goto do_fixup;
> +unlock:
> + spin_unlock(&mm->page_table_lock);
> + if (page)
> + put_page(page);
>
> - /*
> - * Due to lacking code to migrate thp pages, we'll split
> - * (which preserves the special PROT_NONE) and re-take the
> - * fault on the normal pages.
> - */
> - split_huge_page(page);
> - put_page(page);
> return;
>
> -do_fixup:
> +migrate:
> + spin_unlock(&mm->page_table_lock);
> +
> + lock_page(page);
> spin_lock(&mm->page_table_lock);
> - if (unlikely(!pmd_same(*pmd, entry)))
> - goto out_unlock;
> -#endif
> + if (unlikely(!pmd_same(*pmd, entry))) {
> + spin_unlock(&mm->page_table_lock);
> + unlock_page(page);
> + put_page(page);
> + return;
> + }
> + spin_unlock(&mm->page_table_lock);
>
> - /* change back to regular protection */
> - entry = pmd_modify(entry, vma->vm_page_prot);
> - if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
> - update_mmu_cache_pmd(vma, address, entry);
> + new_page = alloc_pages_node(node,
> + (GFP_TRANSHUGE | GFP_THISNODE) & ~__GFP_WAIT,
> + HPAGE_PMD_ORDER);
>
> -out_unlock:
> + if (!new_page)
> + goto alloc_fail;
> +
> + lru = PageLRU(page);
> +
> + if (lru && isolate_lru_page(page)) /* does an implicit get_page() */
> + goto alloc_fail;
> +
> + if (!trylock_page(new_page))
> + BUG();
> +
> + /* anon mapping, we can simply copy page->mapping to the new page: */
> + new_page->mapping = page->mapping;
> + new_page->index = page->index;
> +
> + migrate_page_copy(new_page, page);
> +
> + WARN_ON(PageLRU(new_page));
> +
> + spin_lock(&mm->page_table_lock);
> + if (unlikely(!pmd_same(*pmd, entry))) {
> + spin_unlock(&mm->page_table_lock);
> + if (lru)
> + putback_lru_page(page);
> +
> + unlock_page(new_page);
> + ClearPageActive(new_page); /* Set by migrate_page_copy() */
> + new_page->mapping = NULL;
> + put_page(new_page); /* Free it */
> +
> + unlock_page(page);
> + put_page(page); /* Drop the local reference */
> +
> + return;
> + }
> +
> + entry = mk_pmd(new_page, vma->vm_page_prot);
> + entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
> + entry = pmd_mkhuge(entry);
> +
> + page_add_new_anon_rmap(new_page, vma, haddr);
> +
> + set_pmd_at(mm, haddr, pmd, entry);
> + update_mmu_cache_pmd(vma, address, entry);
> + page_remove_rmap(page);
> spin_unlock(&mm->page_table_lock);
> - if (page)
> +
> + put_page(page); /* Drop the rmap reference */
> +
> + if (lru)
> + put_page(page); /* drop the LRU isolation reference */
> +
> + unlock_page(new_page);
> + unlock_page(page);
> + put_page(page); /* Drop the local reference */
> +
> + return;
> +
> +alloc_fail:
> + if (new_page)
> + put_page(new_page);
> +
> + unlock_page(page);
> +
> + spin_lock(&mm->page_table_lock);
> + if (unlikely(!pmd_same(*pmd, entry))) {
> put_page(page);
> + page = NULL;
> + goto unlock;
> + }
> + goto fixup;
> }
>
> int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 3299949..72d1056 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -417,7 +417,7 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
> */
> void migrate_page_copy(struct page *newpage, struct page *page)
> {
> - if (PageHuge(page))
> + if (PageHuge(page) || PageTransHuge(page))
> copy_huge_page(newpage, page);
> else
> copy_highpage(newpage, page);
> --
> 1.7.11.7
>
> --
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