linux-kernel - Re: [PATCH] vmemmap, memory_hotplug: fallback to base pages for vmmap

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Date:   Wed, 12 Jul 2017 11:03:42 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Cristopher Lameter <cl@...ux.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] vmemmap, memory_hotplug: fallback to base pages for vmmap

On Tue 11-07-17 17:45:41, Johannes Weiner wrote:
[...]
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index a56c3989f773..efd3f48c667c 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -52,18 +52,24 @@ void * __meminit vmemmap_alloc_block(unsigned long size, int node)
>  {
>  	/* If the main allocator is up use that, fallback to bootmem. */
>  	if (slab_is_available()) {
> +		unsigned int order;
> +		static int warned;
>  		struct page *page;
> +		gfp_t gfp_mask;
>  
> +		order = get_order(size);
> +		gfp_mask = GFP_KERNEL|__GFP_ZERO|__GFP_REPEAT|__GFP_NOWARN;

why not do
		gfp_mask = GFP_KERNEL|__GFP_ZERO|__GFP_REPEAT;
		if (warned)
			gfp_mask |= __GFP_NOWARN;

and get the actual allocation warning from the allocation context. Then
we can keep the warning vmemmap_populate_hugepages because that would be
more descriptive that what is going on.

Btw. __GFP_REPEAT has been replaced by __GFP_RETRY_MAYFAIL in mmotm
tree.

>  		if (node_state(node, N_HIGH_MEMORY))
> -			page = alloc_pages_node(
> -				node, GFP_KERNEL | __GFP_ZERO | __GFP_REPEAT,
> -				get_order(size));
> +			page = alloc_pages_node(node, gfp_mask, size);
>  		else
> -			page = alloc_pages(
> -				GFP_KERNEL | __GFP_ZERO | __GFP_REPEAT,
> -				get_order(size));
> +			page = alloc_pages(gfp_mask, size);
>  		if (page)
>  			return page_address(page);
> +		if (!warned) {
> +			warn_alloc(gfp_mask, NULL,
> +				   "vmemmap alloc failure: order:%u", order);
> +			warned = 1;
> +		}
>  		return NULL;
>  	} else
>  		return __earlyonly_bootmem_alloc(node, size, size,

-- 
Michal Hocko
SUSE Labs