linux-kernel - Re: [PATCH] mm: add free_hot_cold_page

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Date:	Mon, 29 Aug 2011 16:48:46 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: add free_hot_cold_page_list helper

On Fri, Jul 29, 2011 at 4:58 PM, Konstantin Khlebnikov
<khlebnikov@...nvz.org> wrote:
> This patch adds helper free_hot_cold_page_list() to free list of 0-order pages.
> It frees pages directly from list without temporary page-vector.
> It also calls trace_mm_pagevec_free() to simulate pagevec_free() behaviour.
>
> bloat-o-meter:
>
> add/remove: 1/1 grow/shrink: 1/3 up/down: 267/-295 (-28)
> function                                     old     new   delta
> free_hot_cold_page_list                        -     264    +264
> get_page_from_freelist                      2129    2132      +3
> __pagevec_free                               243     239      -4
> split_free_page                              380     373      -7
> release_pages                                606     510     -96
> free_page_list                               188       -    -188
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
> ---
>  include/linux/gfp.h |    1 +
>  mm/page_alloc.c     |   12 ++++++++++++
>  mm/swap.c           |   14 +++-----------
>  mm/vmscan.c         |   20 +-------------------
>  4 files changed, 17 insertions(+), 30 deletions(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index cb40892..dd7b9cc 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -358,6 +358,7 @@ void *alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask);
>  extern void __free_pages(struct page *page, unsigned int order);
>  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);
>
>  #define __free_page(page) __free_pages((page), 0)
>  #define free_page(addr) free_pages((addr), 0)
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 1dbcf88..af486e4 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1209,6 +1209,18 @@ out:
>        local_irq_restore(flags);
>  }
>
> +void free_hot_cold_page_list(struct list_head *list, int cold)
> +{
> +       struct page *page, *next;
> +
> +       list_for_each_entry_safe(page, next, list, lru) {
> +               trace_mm_pagevec_free(page, cold);


I understand you want to minimize changes without breaking current ABI
with trace tools.
But apparently, It's not a pagvec_free. It just hurts readability.
As I take a look at the code, mm_pagevec_free isn't related to pagevec
but I guess it can represent 0-order pages free because 0-order pages
are freed only by pagevec until now.
So, how about renaming it with mm_page_free or mm_page_free_zero_order?
If you do, you need to do s/MM_PAGEVEC_FREE/MM_FREE_FREE/g in
trace-pagealloc-postprocess.pl.


> +               free_hot_cold_page(page, cold);
> +       }
> +
> +       INIT_LIST_HEAD(list);

Why do we need it?


-- 
Kind regards,
Minchan Kim
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