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Date: Tue, 13 Nov 2012 18:23:13 -0800 (PST)
From: Hugh Dickins <hughd@...gle.com>
To: Johannes Weiner <hannes@...xchg.org>
cc: Ingo Molnar <mingo@...nel.org>, 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>,
Zhouping Liu <zliu@...hat.com>
Subject: Re: [PATCH 21/31] sched, numa, mm: Implement THP migration
On Tue, 13 Nov 2012, Johannes Weiner wrote:
> [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.
Right, yes, I made several fixes there, but never sent out the final
version. And I can't see your fix to the memcg end of THP migration
either - though I've not done much more than scan the Subjects so far,
I've not yet got to grips with yesterday/today's latest approach.
I'll send out two patches, yours and mine, to what's in the current
linux-next and the current mmotm, which I have been testing with in
several contexts; they probably both apply easily to Ingo's new tree.
But I vehemently hope that this all very soon vanishes from linux-next,
and the new stuff is worked on properly for a while, in a separate
development branch of tip, hopefully converging with Mel's.
Hugh
>
> 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
> >
> > --
> > To unsubscribe, send a message with 'unsubscribe linux-mm' in
> > the body to majordomo@...ck.org. For more info on Linux MM,
> > see: http://www.linux-mm.org/ .
> > Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@...ck.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
>
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