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

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Date:	Mon, 31 Oct 2011 13:14:48 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Konstantin Khlebnikov <khlebnikov@...nvz.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: add free_hot_cold_page_list helper

On Mon, 29 Aug 2011 16:48:46 +0900
Minchan Kim <minchan.kim@...il.com> wrote:

> 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?

My email has been horrid for a couple of months (fixed now), so I might
have missed any reply to Minchin's review comments?

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