linux-kernel - Re: [patch -mm] mm, hugetlb: schedule when potentially allocating many hugepages

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Date:   Wed, 7 Jun 2017 21:31:57 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     David Rientjes <rientjes@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch -mm] mm, hugetlb: schedule when potentially allocating
 many hugepages

On 06/07/2017 09:03 PM, David Rientjes wrote:
> A few hugetlb allocators loop while calling the page allocator and can
> potentially prevent rescheduling if the page allocator slowpath is not
> utilized.
> 
> Conditionally schedule when large numbers of hugepages can be allocated.
> 
> Signed-off-by: David Rientjes <rientjes@...gle.com>
> ---
>  Based on -mm only to prevent merge conflicts with
>  "mm/hugetlb.c: warn the user when issues arise on boot due to hugepages"
> 
>  mm/hugetlb.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1754,6 +1754,7 @@ static int gather_surplus_pages(struct hstate *h, int delta)
>  			break;
>  		}
>  		list_add(&page->lru, &surplus_list);
> +		cond_resched();
>  	}
>  	allocated += i;
>  
> @@ -2222,6 +2223,7 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>  		} else if (!alloc_fresh_huge_page(h,
>  					 &node_states[N_MEMORY]))
>  			break;
> +		cond_resched();
>  	}
>  	if (i < h->max_huge_pages) {
>  		char buf[32];
> @@ -2364,6 +2366,7 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
>  			ret = alloc_fresh_gigantic_page(h, nodes_allowed);
>  		else
>  			ret = alloc_fresh_huge_page(h, nodes_allowed);
> +		cond_resched();

Are not the following lines immediately before the above huge page allocation
in set_max_huge_pages, or am I looking at an incorrect version of the file?

		/* yield cpu to avoid soft lockup */
		cond_resched();

-- 
Mike Kravetz

>  		spin_lock(&hugetlb_lock);
>  		if (!ret)
>  			goto out;
> 
> --
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