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    SubjectRe: [PATCH 1/2] mm, thp: introduce dedicated transparent huge page allocation interfaces
    Hi Khandual,
    Thanks for your review.

    On Tue, Oct 17, 2017 at 01:38:07PM +0530, Anshuman Khandual wrote:
    > On 10/16/2017 02:49 PM, changbin.du@intel.com wrote:
    > > From: Changbin Du <changbin.du@intel.com>
    > >
    > > This patch introduced 4 new interfaces to allocate a prepared
    > > transparent huge page.
    > > - alloc_transhuge_page_vma
    > > - alloc_transhuge_page_nodemask
    > > - alloc_transhuge_page_node
    > > - alloc_transhuge_page
    > >
    >
    > If we are trying to match HugeTLB helpers, then it should have
    > format something like alloc_transhugepage_xxx instead of
    > alloc_transhuge_page_XXX. But I think its okay.
    >
    HugeTLB helpers are something like alloc_huge_page, so I think
    alloc_transhuge_page match it. And existing names already have
    *transhuge_page* style.

    > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
    > > index 14bc21c..1dd2c33 100644
    > > --- a/include/linux/huge_mm.h
    > > +++ b/include/linux/huge_mm.h
    > > @@ -130,9 +130,20 @@ extern unsigned long thp_get_unmapped_area(struct file *filp,
    > > unsigned long addr, unsigned long len, unsigned long pgoff,
    > > unsigned long flags);
    > >
    > > -extern void prep_transhuge_page(struct page *page);
    > > extern void free_transhuge_page(struct page *page);
    > >
    > > +struct page *alloc_transhuge_page_vma(gfp_t gfp_mask,
    > > + struct vm_area_struct *vma, unsigned long addr);
    > > +struct page *alloc_transhuge_page_nodemask(gfp_t gfp_mask,
    > > + int preferred_nid, nodemask_t *nmask);
    >
    > Would not they require 'extern' here ?
    >
    Need or not, function declaration are implicitly 'extern'. I will add it to
    align with existing code.

    > > +
    > > +static inline struct page *alloc_transhuge_page_node(int nid, gfp_t gfp_mask)
    > > +{
    > > + return alloc_transhuge_page_nodemask(gfp_mask, nid, NULL);
    > > +}
    > > +
    > > +struct page *alloc_transhuge_page(gfp_t gfp_mask);
    > > +
    > > bool can_split_huge_page(struct page *page, int *pextra_pins);
    > > int split_huge_page_to_list(struct page *page, struct list_head *list);
    > > static inline int split_huge_page(struct page *page)
    > > diff --git a/include/linux/migrate.h b/include/linux/migrate.h
    > > index 643c7ae..70a00f3 100644
    > > --- a/include/linux/migrate.h
    > > +++ b/include/linux/migrate.h
    > > @@ -42,19 +42,15 @@ static inline struct page *new_page_nodemask(struct page *page,
    > > return alloc_huge_page_nodemask(page_hstate(compound_head(page)),
    > > preferred_nid, nodemask);
    > >
    > > - if (thp_migration_supported() && PageTransHuge(page)) {
    > > - order = HPAGE_PMD_ORDER;
    > > - gfp_mask |= GFP_TRANSHUGE;
    > > - }
    > > -
    > > if (PageHighMem(page) || (zone_idx(page_zone(page)) == ZONE_MOVABLE))
    > > gfp_mask |= __GFP_HIGHMEM;
    > >
    > > - new_page = __alloc_pages_nodemask(gfp_mask, order,
    > > + if (thp_migration_supported() && PageTransHuge(page))
    > > + return alloc_transhuge_page_nodemask(gfp_mask | GFP_TRANSHUGE,
    > > + preferred_nid, nodemask);
    > > + else
    > > + return __alloc_pages_nodemask(gfp_mask, order,
    > > preferred_nid, nodemask);
    > > -
    > > - if (new_page && PageTransHuge(page))
    > > - prep_transhuge_page(new_page);
    >
    > This makes sense, calling prep_transhuge_page() inside the
    > function alloc_transhuge_page_nodemask() is better I guess.
    >
    > >
    > > return new_page;
    > > }
    > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
    > > index 269b5df..e267488 100644
    > > --- a/mm/huge_memory.c
    > > +++ b/mm/huge_memory.c
    > > @@ -490,7 +490,7 @@ static inline struct list_head *page_deferred_list(struct page *page)
    > > return (struct list_head *)&page[2].mapping;
    > > }
    > >
    > > -void prep_transhuge_page(struct page *page)
    > > +static void prep_transhuge_page(struct page *page)
    >
    > Right. It wont be used outside huge page allocation context and
    > you have already mentioned about it.
    >
    > > {
    > > /*
    > > * we use page->mapping and page->indexlru in second tail page
    > > @@ -501,6 +501,45 @@ void prep_transhuge_page(struct page *page)
    > > set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
    > > }
    > >
    > > +struct page *alloc_transhuge_page_vma(gfp_t gfp_mask,
    > > + struct vm_area_struct *vma, unsigned long addr)
    > > +{
    > > + struct page *page;
    > > +
    > > + page = alloc_pages_vma(gfp_mask | __GFP_COMP, HPAGE_PMD_ORDER,
    > > + vma, addr, numa_node_id(), true);
    > > + if (unlikely(!page))
    > > + return NULL;
    > > + prep_transhuge_page(page);
    > > + return page;
    > > +}
    >
    > __GFP_COMP and HPAGE_PMD_ORDER are the minimum flags which will be used
    > for huge page allocation and preparation. Any thing else depending upon
    > the context will be passed by the caller. Makes sense.
    >
    yes, thanks.

    > > +
    > > +struct page *alloc_transhuge_page_nodemask(gfp_t gfp_mask,
    > > + int preferred_nid, nodemask_t *nmask)
    > > +{
    > > + struct page *page;
    > > +
    > > + page = __alloc_pages_nodemask(gfp_mask | __GFP_COMP, HPAGE_PMD_ORDER,
    > > + preferred_nid, nmask);
    > > + if (unlikely(!page))
    > > + return NULL;
    > > + prep_transhuge_page(page);
    > > + return page;
    > > +}
    > > +
    >
    > Same here.
    >
    > > +struct page *alloc_transhuge_page(gfp_t gfp_mask)
    > > +{
    > > + struct page *page;
    > > +
    > > + VM_BUG_ON(!(gfp_mask & __GFP_COMP));
    >
    > You expect the caller to provide __GFP_COMP, why ? You are
    > anyways providing it later.
    >
    oops, I forgot to update this line. Will remove it. Thanks for figuring it out.

    --
    Thanks,
    Changbin Du
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