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SubjectRe: [patch 11/11] mm: memcg: remove unused node/section info from pc->flags
On Mon 12-09-11 12:57:28, Johannes Weiner wrote:
> To find the page corresponding to a certain page_cgroup, the pc->flags
> encoded the node or section ID with the base array to compare the pc
> pointer to.
>
> Now that the per-memory cgroup LRU lists link page descriptors
> directly, there is no longer any code that knows the page_cgroup but
> not the page.
>
> Signed-off-by: Johannes Weiner <jweiner@redhat.com>

Nice.
Reviewed-by: Michal Hocko <mhocko@suse.cz>

> ---
> include/linux/page_cgroup.h | 33 ------------------------
> mm/page_cgroup.c | 58 ++++++-------------------------------------
> 2 files changed, 8 insertions(+), 83 deletions(-)
>
> diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
> index 5bae753..aaa60da 100644
> --- a/include/linux/page_cgroup.h
> +++ b/include/linux/page_cgroup.h
> @@ -121,39 +121,6 @@ static inline void move_unlock_page_cgroup(struct page_cgroup *pc,
> local_irq_restore(*flags);
> }
>
> -#ifdef CONFIG_SPARSEMEM
> -#define PCG_ARRAYID_WIDTH SECTIONS_SHIFT
> -#else
> -#define PCG_ARRAYID_WIDTH NODES_SHIFT
> -#endif
> -
> -#if (PCG_ARRAYID_WIDTH > BITS_PER_LONG - NR_PCG_FLAGS)
> -#error Not enough space left in pc->flags to store page_cgroup array IDs
> -#endif
> -
> -/* pc->flags: ARRAY-ID | FLAGS */
> -
> -#define PCG_ARRAYID_MASK ((1UL << PCG_ARRAYID_WIDTH) - 1)
> -
> -#define PCG_ARRAYID_OFFSET (BITS_PER_LONG - PCG_ARRAYID_WIDTH)
> -/*
> - * Zero the shift count for non-existent fields, to prevent compiler
> - * warnings and ensure references are optimized away.
> - */
> -#define PCG_ARRAYID_SHIFT (PCG_ARRAYID_OFFSET * (PCG_ARRAYID_WIDTH != 0))
> -
> -static inline void set_page_cgroup_array_id(struct page_cgroup *pc,
> - unsigned long id)
> -{
> - pc->flags &= ~(PCG_ARRAYID_MASK << PCG_ARRAYID_SHIFT);
> - pc->flags |= (id & PCG_ARRAYID_MASK) << PCG_ARRAYID_SHIFT;
> -}
> -
> -static inline unsigned long page_cgroup_array_id(struct page_cgroup *pc)
> -{
> - return (pc->flags >> PCG_ARRAYID_SHIFT) & PCG_ARRAYID_MASK;
> -}
> -
> #else /* CONFIG_CGROUP_MEM_RES_CTLR */
> struct page_cgroup;
>
> diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
> index 256dee8..2601a65 100644
> --- a/mm/page_cgroup.c
> +++ b/mm/page_cgroup.c
> @@ -11,12 +11,6 @@
> #include <linux/swapops.h>
> #include <linux/kmemleak.h>
>
> -static void __meminit init_page_cgroup(struct page_cgroup *pc, unsigned long id)
> -{
> - pc->flags = 0;
> - set_page_cgroup_array_id(pc, id);
> - pc->mem_cgroup = NULL;
> -}
> static unsigned long total_usage;
>
> #if !defined(CONFIG_SPARSEMEM)
> @@ -41,24 +35,11 @@ struct page_cgroup *lookup_page_cgroup(struct page *page)
> return base + offset;
> }
>
> -struct page *lookup_cgroup_page(struct page_cgroup *pc)
> -{
> - unsigned long pfn;
> - struct page *page;
> - pg_data_t *pgdat;
> -
> - pgdat = NODE_DATA(page_cgroup_array_id(pc));
> - pfn = pc - pgdat->node_page_cgroup + pgdat->node_start_pfn;
> - page = pfn_to_page(pfn);
> - VM_BUG_ON(pc != lookup_page_cgroup(page));
> - return page;
> -}
> -
> static int __init alloc_node_page_cgroup(int nid)
> {
> - struct page_cgroup *base, *pc;
> + struct page_cgroup *base;
> unsigned long table_size;
> - unsigned long start_pfn, nr_pages, index;
> + unsigned long nr_pages;
>
> start_pfn = NODE_DATA(nid)->node_start_pfn;
> nr_pages = NODE_DATA(nid)->node_spanned_pages;
> @@ -72,10 +53,6 @@ static int __init alloc_node_page_cgroup(int nid)
> table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
> if (!base)
> return -ENOMEM;
> - for (index = 0; index < nr_pages; index++) {
> - pc = base + index;
> - init_page_cgroup(pc, nid);
> - }
> NODE_DATA(nid)->node_page_cgroup = base;
> total_usage += table_size;
> return 0;
> @@ -116,31 +93,19 @@ struct page_cgroup *lookup_page_cgroup(struct page *page)
> return section->page_cgroup + pfn;
> }
>
> -struct page *lookup_cgroup_page(struct page_cgroup *pc)
> -{
> - struct mem_section *section;
> - struct page *page;
> - unsigned long nr;
> -
> - nr = page_cgroup_array_id(pc);
> - section = __nr_to_section(nr);
> - page = pfn_to_page(pc - section->page_cgroup);
> - VM_BUG_ON(pc != lookup_page_cgroup(page));
> - return page;
> -}
> -
> static void *__meminit alloc_page_cgroup(size_t size, int nid)
> {
> void *addr = NULL;
>
> - addr = alloc_pages_exact_nid(nid, size, GFP_KERNEL | __GFP_NOWARN);
> + addr = alloc_pages_exact_nid(nid, size,
> + GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN);
> if (addr)
> return addr;
>
> if (node_state(nid, N_HIGH_MEMORY))
> - addr = vmalloc_node(size, nid);
> + addr = vzalloc_node(size, nid);
> else
> - addr = vmalloc(size);
> + addr = vzalloc(size);
>
> return addr;
> }
> @@ -163,14 +128,11 @@ static void free_page_cgroup(void *addr)
>
> static int __meminit init_section_page_cgroup(unsigned long pfn, int nid)
> {
> - struct page_cgroup *base, *pc;
> struct mem_section *section;
> + struct page_cgroup *base;
> unsigned long table_size;
> - unsigned long nr;
> - int index;
>
> - nr = pfn_to_section_nr(pfn);
> - section = __nr_to_section(nr);
> + section = __pfn_to_section(pfn);
>
> if (section->page_cgroup)
> return 0;
> @@ -190,10 +152,6 @@ static int __meminit init_section_page_cgroup(unsigned long pfn, int nid)
> return -ENOMEM;
> }
>
> - for (index = 0; index < PAGES_PER_SECTION; index++) {
> - pc = base + index;
> - init_page_cgroup(pc, nr);
> - }
> /*
> * The passed "pfn" may not be aligned to SECTION. For the calculation
> * we need to apply a mask.
> --
> 1.7.6
>
> --
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--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic


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