linux-kernel - Re: [RFC PATCH 5/8] hugetlb: change free_pool_huge_page to remove_pool_huge

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Message-ID: <YFiqJSGjMMG3diWp@dhcp22.suse.cz>
Date:   Mon, 22 Mar 2021 15:31:01 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Muchun Song <songmuchun@...edance.com>,
        David Rientjes <rientjes@...gle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        HORIGUCHI NAOYA <naoya.horiguchi@....com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Waiman Long <longman@...hat.com>, Peter Xu <peterx@...hat.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH 5/8] hugetlb: change free_pool_huge_page to
 remove_pool_huge_page

On Fri 19-03-21 15:42:06, Mike Kravetz wrote:
[...]
> @@ -2090,9 +2084,15 @@ static void return_unused_surplus_pages(struct hstate *h,
>  	while (nr_pages--) {
>  		h->resv_huge_pages--;
>  		unused_resv_pages--;
> -		if (!free_pool_huge_page(h, &node_states[N_MEMORY], 1))
> +		page = remove_pool_huge_page(h, &node_states[N_MEMORY], 1);
> +		if (!page)
>  			goto out;
> -		cond_resched_lock(&hugetlb_lock);
> +
> +		/* Drop lock and free page to buddy as it could sleep */
> +		spin_unlock(&hugetlb_lock);
> +		update_and_free_page(h, page);
> +		cond_resched();
> +		spin_lock(&hugetlb_lock);
>  	}
>  
>  out:

This is likely a matter of taste but the repeated pattern of unlock,
update_and_free_page, cond_resched and lock seems rather clumsy.
Would it be slightly better/nicer to remove_pool_huge_page into a
list_head under a single lock invocation and then free up the whole lot
after the lock is dropped?

-- 
Michal Hocko
SUSE Labs