Date: Tue, 18 Mar 2008 12:23:02 +0000
From: Mel Gorman <mel@csn.ul.ie>
To: Andi Kleen <andi@firstfloor.org>
Cc: linux-kernel@vger.kernel.org, pj@sgi.com, linux-mm@kvack.org,
       nickpiggin@yahoo.com.au
Subject: Re: [PATCH] [2/18] Add basic support for more than one hstate in hugetlbfs
Message-ID: <20080318122302.GB23866@csn.ul.ie>
References: <20080317258.659191058@firstfloor.org> <20080317015815.D43991B41E0@basil.firstfloor.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-15
Content-Disposition: inline
In-Reply-To: <20080317015815.D43991B41E0@basil.firstfloor.org>
User-Agent: Mutt/1.5.13 (2006-08-11)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 4385
Lines: 145

On (17/03/08 02:58), Andi Kleen didst pronounce:
> - Convert hstates to an array
> - Add a first default entry covering the standard huge page size
> - Add functions for architectures to register new hstates
> - Add basic iterators over hstates
> 
> Signed-off-by: Andi Kleen <ak@suse.de>
> 
> ---
>  include/linux/hugetlb.h |   10 +++++++++-
>  mm/hugetlb.c            |   46 +++++++++++++++++++++++++++++++++++++---------
>  2 files changed, 46 insertions(+), 10 deletions(-)
> 
> Index: linux/mm/hugetlb.c
> ===================================================================
> --- linux.orig/mm/hugetlb.c
> +++ linux/mm/hugetlb.c
> @@ -27,7 +27,15 @@ unsigned long sysctl_overcommit_huge_pag
>  static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
>  unsigned long hugepages_treat_as_movable;
>  
> -struct hstate global_hstate;
> +static int max_hstate = 1;
> +
> +struct hstate hstates[HUGE_MAX_HSTATE];
> +
> +/* for command line parsing */
> +struct hstate *parsed_hstate __initdata = &global_hstate;
> +

global_hstate becomes a misleading name in this patch. default_hstate
minimally

> +#define for_each_hstate(h) \
> +	for ((h) = hstates; (h) < &hstates[max_hstate]; (h)++)
>  
>  /*
>   * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
> @@ -474,15 +482,11 @@ static struct page *alloc_huge_page(stru
>  	return page;
>  }
>  
> -static int __init hugetlb_init(void)
> +static int __init hugetlb_init_hstate(struct hstate *h)
>  {
>  	unsigned long i;
> -	struct hstate *h = &global_hstate;
>  
> -	if (HPAGE_SHIFT == 0)
> -		return 0;
> -

Why is there no need for

if (huge_page_shift(h) == 0)
	return 0;
?

ah, it's because of what you do to hugetlb_init().

> -	if (!h->order) {
> +	if (h == &global_hstate && !h->order) {
>  		h->order = HPAGE_SHIFT - PAGE_SHIFT;
>  		h->mask = HPAGE_MASK;
>  	}
> @@ -497,11 +501,34 @@ static int __init hugetlb_init(void)
>  			break;
>  	}
>  	max_huge_pages = h->free_huge_pages = h->nr_huge_pages = i;
> -	printk("Total HugeTLB memory allocated, %ld\n", h->free_huge_pages);
> +
> +	printk(KERN_INFO "Total HugeTLB memory allocated, %ld %dMB pages\n",
> +			h->free_huge_pages,
> +			1 << (h->order + PAGE_SHIFT - 20));

Ah, you partially fix up my whinge from the previous patch here.

page_alloc.c has a helper called K() for conversions. Perhaps move it to
internal.h and add one for M instead of the - 20 here? Not a big deal as
it doesn't take long to figure out.

>  	return 0;
>  }
> +
> +static int __init hugetlb_init(void)
> +{
> +	if (HPAGE_SHIFT == 0)
> +		return 0;
> +	return hugetlb_init_hstate(&global_hstate);
> +}
>  module_init(hugetlb_init);
>  
> +/* Should be called on processing a hugepagesz=... option */
> +void __init huge_add_hstate(unsigned order)
> +{
> +	struct hstate *h;
> +	BUG_ON(max_hstate >= HUGE_MAX_HSTATE);
> +	BUG_ON(order <= HPAGE_SHIFT - PAGE_SHIFT);
> +	h = &hstates[max_hstate++];
> +	h->order = order;
> +	h->mask = ~((1ULL << (order + PAGE_SHIFT)) - 1);
> +	hugetlb_init_hstate(h);
> +	parsed_hstate = h;
> +}

It's not clear in this patch what parsed_hstate is for as it is not used
elsewhere. I've made a note to check if parsed_hstate makes an unwritten
assumption that there is only "one other" huge page size in the system.

> +
>  static int __init hugetlb_setup(char *s)
>  {
>  	if (sscanf(s, "%lu", &max_huge_pages) <= 0)
> Index: linux/include/linux/hugetlb.h
> ===================================================================
> --- linux.orig/include/linux/hugetlb.h
> +++ linux/include/linux/hugetlb.h
> @@ -213,7 +213,15 @@ struct hstate {
>  	unsigned int surplus_huge_pages_node[MAX_NUMNODES];
>  };
>  
> -extern struct hstate global_hstate;
> +void __init huge_add_hstate(unsigned order);
> +
> +#ifndef HUGE_MAX_HSTATE
> +#define HUGE_MAX_HSTATE 1
> +#endif
> +
> +extern struct hstate hstates[HUGE_MAX_HSTATE];
> +
> +#define global_hstate (hstates[0])
>  
>  static inline struct hstate *hstate_vma(struct vm_area_struct *vma)
>  {
> 

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/