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Message-ID: <20080318122302.GB23866@csn.ul.ie>
Date: Tue, 18 Mar 2008 12:23:02 +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] [2/18] Add basic support for more than one hstate in hugetlbfs
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@...e.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
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