linux-kernel - Re: [PATCH] page-allocator: Remove dead function free_cold

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Message-ID: <20090806162539.GE6915@csn.ul.ie>
Date:	Thu, 6 Aug 2009 17:25:39 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: [PATCH] page-allocator: Remove dead function free_cold_page()

On Wed, Aug 05, 2009 at 06:52:47PM -0700, Andrew Morton wrote:
> On Wed, 5 Aug 2009 11:28:17 +0100 Mel Gorman <mel@....ul.ie> wrote:
> 
> > The function free_cold_page() has no callers so delete it.
> > 
> > Signed-off-by: Mel Gorman <mel@....ul.ie>
> > --- 
> >  include/linux/gfp.h |    1 -
> >  mm/page_alloc.c     |    5 -----
> >  2 files changed, 6 deletions(-)
> > 
> > diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> > index 7c777a0..c32bfa8 100644
> > --- a/include/linux/gfp.h
> > +++ b/include/linux/gfp.h
> > @@ -326,7 +326,6 @@ void free_pages_exact(void *virt, size_t size);
> >  extern void __free_pages(struct page *page, unsigned int order);
> >  extern void free_pages(unsigned long addr, unsigned int order);
> >  extern void free_hot_page(struct page *page);
> > -extern void free_cold_page(struct page *page);
> >  
> >  #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 d052abb..36758db 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1065,11 +1065,6 @@ void free_hot_page(struct page *page)
> >  	free_hot_cold_page(page, 0);
> >  }
> >  	
> > -void free_cold_page(struct page *page)
> > -{
> > -	free_hot_cold_page(page, 1);
> > -}
> > -
> >  /*
> >   * split_page takes a non-compound higher-order page, and splits it into
> >   * n (1<<order) sub-pages: page[0..n]
> 
> Well I spose so.  But the function is valid and might need to be
> resurrected at any stage.  We could `#if 0' it to save a few bytes of
> text, perhaps.
> 

We could although the code is so trivial, it's not like it's hard to
reimplement.

> I wonder how many free_page() callers should really be calling
> free_cold_page().  c'mon, write a thingy to work it out ;) You can
> query a page's hotness by timing how long it takes to read all its
> cachelines.
> 

Hmm, interesting idea, I'll give it more of a think and see what falls
out!

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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