linux-kernel - Re: [PATCH 09/10] memory-hotplug: enable memory hotplug to handle hugepage

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Date:	Tue, 26 Mar 2013 17:31:51 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>, linux-mm@...ck.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, Hugh Dickins <hughd@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Hillf Danton <dhillf@...il.com>, Michal Hocko <mhocko@...e.cz>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/10] memory-hotplug: enable memory hotplug to handle hugepage

Naoya Horiguchi <n-horiguchi@...jp.nec.com> writes:

> +/* Returns true for head pages of in-use hugepages, otherwise returns false. */
> +bool is_hugepage_movable(struct page *hpage)
> +{
> +	struct page *page;
> +	struct hstate *h;
> +	bool ret = false;
> +
> +	VM_BUG_ON(!PageHuge(hpage));
> +	/*
> +	 * This function can be called for a tail page because memory hotplug
> +	 * scans movability of pages by pfn range of a memory block.
> +	 * Larger hugepages (1GB for x86_64) are larger than memory block, so
> +	 * the scan can start at the tail page of larger hugepages.
> +	 * 1GB hugepage is not movable now, so we return with false for now.
> +	 */
> +	if (PageTail(hpage))
> +		return false;
> +	h = page_hstate(hpage);
> +	spin_lock(&hugetlb_lock);
> +	list_for_each_entry(page, &h->hugepage_activelist, lru)
> +		if (page == hpage) {
> +			ret = true;
> +			break;
> +		}
> +	spin_unlock(&hugetlb_lock);
> +	return ret;
> +}
> +

May be is_hugepage_active() ?


-aneesh

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