linux-kernel - Re: [PATCH] [4/18] Add basic support for more than one hstate in hugetlbfs

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Date:	Tue, 18 Mar 2008 14:11:40 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	linux-kernel@...r.kernel.org, pj@....com, linux-mm@...ck.org,
	nickpiggin@...oo.com.au
Subject: Re: [PATCH] [4/18] Add basic support for more than one hstate in hugetlbfs

Missing leader and the subject is misleading as to what the patch is
doing. Am assuming this is an accident.

On (17/03/08 02:58), Andi Kleen didst pronounce:
> Signed-off-by: Andi Kleen <ak@...e.de>
> 
> ---
>  mm/hugetlb.c |   15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> Index: linux/mm/hugetlb.c
> ===================================================================
> --- linux.orig/mm/hugetlb.c
> +++ linux/mm/hugetlb.c
> @@ -550,26 +550,33 @@ static unsigned int cpuset_mems_nr(unsig
>  
>  #ifdef CONFIG_SYSCTL
>  #ifdef CONFIG_HIGHMEM
> -static void try_to_free_low(unsigned long count)
> +static void do_try_to_free_low(struct hstate *h, unsigned long count)
>  {
> -	struct hstate *h = &global_hstate;
>  	int i;
>  
>  	for (i = 0; i < MAX_NUMNODES; ++i) {
>  		struct page *page, *next;
>  		struct list_head *freel = &h->hugepage_freelists[i];
>  		list_for_each_entry_safe(page, next, freel, lru) {
> -			if (count >= nr_huge_pages)
> +			if (count >= h->nr_huge_pages)
>  				return;
>  			if (PageHighMem(page))
>  				continue;
>  			list_del(&page->lru);
> -			update_and_free_page(page);
> +			update_and_free_page(h, page);
>  			h->free_huge_pages--;
>  			h->free_huge_pages_node[page_to_nid(page)]--;
>  		}
>  	}
>  }
> +
> +static void try_to_free_low(unsigned long count)
> +{
> +	struct hstate *h;
> +	for_each_hstate (h) {
> +		do_try_to_free_low(h, count);
> +	}
> +}

hmm, so this is freeing 'count' pages from all pools. I doubt that's what
you really want to be doing here. If someone if using the proc entries to
shrink a pool size, I imagine they want to shrink X pages of size Y from a
single pool, not shrink X pages from all pools.

What am I missing?

>  #else
>  static inline void try_to_free_low(unsigned long count)
>  {
> 
> --
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> 

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