Re: [PATCH] mm/hugetlb: Warn the user when issues arise on boot due to hugepages

[Michal Hocko <mhocko@suse.com>]

On Fri 02-06-17 20:54:13, Liam R. Howlett wrote:
> When the user specifies too many hugepages or an invalid
> default_hugepagesz the communication to the user is implicit in the
> allocation message.  This patch adds a warning when the desired page
> count is not allocated and prints an error when the default_hugepagesz
> is invalid on boot.

We do not warn when doing echo $NUM > nr_hugepages, so why should we
behave any different during the boot?
 
> Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
> ---
>  mm/hugetlb.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index e5828875f7bb..6de30bbac23e 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -70,6 +70,7 @@ struct mutex *hugetlb_fault_mutex_table ____cacheline_aligned_in_smp;
>  
>  /* Forward declaration */
>  static int hugetlb_acct_memory(struct hstate *h, long delta);
> +static char * __init memfmt(char *buf, unsigned long n);
>  
>  static inline void unlock_or_release_subpool(struct hugepage_subpool *spool)
>  {
> @@ -2189,7 +2190,14 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>  					 &node_states[N_MEMORY]))
>  			break;
>  	}
> -	h->max_huge_pages = i;
> +	if (i < h->max_huge_pages) {
> +		char buf[32];
> +
> +		memfmt(buf, huge_page_size(h)),
> +		pr_warn("HugeTLB: allocating %lu of page size %s failed.  Only allocated %lu hugepages.\n",
> +			h->max_huge_pages, buf, i);
> +		h->max_huge_pages = i;
> +	}
>  }
>  
>  static void __init hugetlb_init_hstates(void)
> @@ -2785,6 +2793,11 @@ static int __init hugetlb_init(void)
>  		return 0;
>  
>  	if (!size_to_hstate(default_hstate_size)) {
> +		if (default_hstate_size != 0) {
> +			pr_err("HugeTLB: unsupported default_hugepagesz %lu. Reverting to %lu\n",
> +			       default_hstate_size, HPAGE_SIZE);
> +		}
> +
>  		default_hstate_size = HPAGE_SIZE;
>  		if (!size_to_hstate(default_hstate_size))
>  			hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
> -- 
> 2.13.0.92.gcd65a7235
> 

-- 
Michal Hocko
SUSE Labs

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