linux-kernel - Re: [PATCH v10 09/11] mm/hugetlb: Introduce nr_free_vmemmap

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Date:   Mon, 21 Dec 2020 09:16:54 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     corbet@....net, mike.kravetz@...cle.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
        paulmck@...nel.org, mchehab+huawei@...nel.org,
        pawan.kumar.gupta@...ux.intel.com, rdunlap@...radead.org,
        oneukum@...e.com, anshuman.khandual@....com, jroedel@...e.de,
        almasrymina@...gle.com, rientjes@...gle.com, willy@...radead.org,
        mhocko@...e.com, song.bao.hua@...ilicon.com, david@...hat.com,
        naoya.horiguchi@....com, duanxiongchun@...edance.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v10 09/11] mm/hugetlb: Introduce nr_free_vmemmap_pages in
 the struct hstate

On Thu, Dec 17, 2020 at 08:13:01PM +0800, Muchun Song wrote:
> @@ -182,6 +184,12 @@ bool hugetlb_free_vmemmap_enabled;
>  
>  static int __init early_hugetlb_free_vmemmap_param(char *buf)
>  {
> +	/* We cannot optimize if a "struct page" crosses page boundaries. */
> +	if ((!is_power_of_2(sizeof(struct page)))) {
> +		pr_warn("cannot free vmemmap pages because \"struct page\" crosses page boundaries\n");
> +		return 0;
> +	}

Unless there is a strong reason behind, I would move this to the previous patch,
where early_hugetlb_free_vmemmap_param is introduced.

-- 
Oscar Salvador
SUSE L3