linux-kernel - Re: [PATCH -mm v2.1] mm: get rid of __GFP

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Message-ID: <xr934n2bjuec.fsf@gthelen.mtv.corp.google.com>
Date:	Wed, 02 Apr 2014 14:25:47 -0700
From:	Greg Thelen <gthelen@...gle.com>
To:	Vladimir Davydov <vdavydov@...allels.com>
Cc:	akpm@...ux-foundation.org, hannes@...xchg.org, mhocko@...e.cz,
	glommer@...il.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, devel@...nvz.org
Subject: Re: [PATCH -mm v2.1] mm: get rid of __GFP_KMEMCG


On Tue, Apr 01 2014, Vladimir Davydov <vdavydov@...allels.com> wrote:

> Currently to allocate a page that should be charged to kmemcg (e.g.
> threadinfo), we pass __GFP_KMEMCG flag to the page allocator. The page
> allocated is then to be freed by free_memcg_kmem_pages. Apart from
> looking asymmetrical, this also requires intrusion to the general
> allocation path. So let's introduce separate functions that will
> alloc/free pages charged to kmemcg.
>
> The new functions are called alloc_kmem_pages and free_kmem_pages. They
> should be used when the caller actually would like to use kmalloc, but
> has to fall back to the page allocator for the allocation is large. They
> only differ from alloc_pages and free_pages in that besides allocating
> or freeing pages they also charge them to the kmem resource counter of
> the current memory cgroup.
>
> Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>

One comment nit below, otherwise looks good to me.

Acked-by: Greg Thelen <gthelen@...gle.com>

> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Michal Hocko <mhocko@...e.cz>
> Cc: Glauber Costa <glommer@...il.com>
> Cc: Christoph Lameter <cl@...ux-foundation.org>
> Cc: Pekka Enberg <penberg@...nel.org>
> ---
> Changes in v2.1:
>  - add missing kmalloc_order forward declaration; lacking it caused
>    compilation breakage with CONFIG_TRACING=n
>
>  include/linux/gfp.h             |   10 ++++---
>  include/linux/memcontrol.h      |    2 +-
>  include/linux/slab.h            |   11 +-------
>  include/linux/thread_info.h     |    2 --
>  include/trace/events/gfpflags.h |    1 -
>  kernel/fork.c                   |    6 ++---
>  mm/page_alloc.c                 |   56 ++++++++++++++++++++++++---------------
>  mm/slab_common.c                |   12 +++++++++
>  mm/slub.c                       |    6 ++---
>  9 files changed, 61 insertions(+), 45 deletions(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 39b81dc7d01a..d382db71e300 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -31,7 +31,6 @@ struct vm_area_struct;
>  #define ___GFP_HARDWALL		0x20000u
>  #define ___GFP_THISNODE		0x40000u
>  #define ___GFP_RECLAIMABLE	0x80000u
> -#define ___GFP_KMEMCG		0x100000u
>  #define ___GFP_NOTRACK		0x200000u
>  #define ___GFP_NO_KSWAPD	0x400000u
>  #define ___GFP_OTHER_NODE	0x800000u
> @@ -91,7 +90,6 @@ struct vm_area_struct;
>  
>  #define __GFP_NO_KSWAPD	((__force gfp_t)___GFP_NO_KSWAPD)
>  #define __GFP_OTHER_NODE ((__force gfp_t)___GFP_OTHER_NODE) /* On behalf of other node */
> -#define __GFP_KMEMCG	((__force gfp_t)___GFP_KMEMCG) /* Allocation comes from a memcg-accounted resource */
>  #define __GFP_WRITE	((__force gfp_t)___GFP_WRITE)	/* Allocator intends to dirty page */
>  
>  /*
> @@ -353,6 +351,10 @@ extern struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
>  #define alloc_page_vma_node(gfp_mask, vma, addr, node)		\
>  	alloc_pages_vma(gfp_mask, 0, vma, addr, node)
>  
> +extern struct page *alloc_kmem_pages(gfp_t gfp_mask, unsigned int order);
> +extern struct page *alloc_kmem_pages_node(int nid, gfp_t gfp_mask,
> +					  unsigned int order);
> +
>  extern unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order);
>  extern unsigned long get_zeroed_page(gfp_t gfp_mask);
>  
> @@ -372,8 +374,8 @@ extern void free_pages(unsigned long addr, unsigned int order);
>  extern void free_hot_cold_page(struct page *page, int cold);
>  extern void free_hot_cold_page_list(struct list_head *list, int cold);
>  
> -extern void __free_memcg_kmem_pages(struct page *page, unsigned int order);
> -extern void free_memcg_kmem_pages(unsigned long addr, unsigned int order);
> +extern void __free_kmem_pages(struct page *page, unsigned int order);
> +extern void free_kmem_pages(unsigned long addr, unsigned int order);
>  
>  #define __free_page(page) __free_pages((page), 0)
>  #define free_page(addr) free_pages((addr), 0)
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 29068dd26c3d..13acdb5259f5 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -543,7 +543,7 @@ memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **memcg, int order)
>  	 * res_counter_charge_nofail, but we hope those allocations are rare,
>  	 * and won't be worth the trouble.
>  	 */

Just a few lines higher in first memcg_kmem_newpage_charge() comment,
there is a leftover reference to GFP_KMEMCG which should be removed.
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