From: Eric Dumazet <eric.dumazet@gmail.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
linux-mm@kvack.org, Andi Kleen <ak@linux.intel.com>,
"H. Peter Anvin" <hpa@linux.intel.com>,
linux-kernel@vger.kernel.org,
"Kirill A. Shutemov" <kirill@shutemov.name>
Subject: Re: [PATCH v2 10/10] thp: implement refcounting for huge zero page
Date: Mon, 10 Sep 2012 16:02:39 +0200 [thread overview]
Message-ID: <1347285759.1234.1645.camel@edumazet-glaptop> (raw)
In-Reply-To: <1347282813-21935-11-git-send-email-kirill.shutemov@linux.intel.com>
On Mon, 2012-09-10 at 16:13 +0300, Kirill A. Shutemov wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>
> H. Peter Anvin doesn't like huge zero page which sticks in memory forever
> after the first allocation. Here's implementation of lockless refcounting
> for huge zero page.
>
...
> +static unsigned long get_huge_zero_page(void)
> +{
> + struct page *zero_page;
> +retry:
> + if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
> + return ACCESS_ONCE(huge_zero_pfn);
> +
> + zero_page = alloc_pages(GFP_TRANSHUGE | __GFP_ZERO, HPAGE_PMD_ORDER);
> + if (!zero_page)
> + return 0;
> + if (cmpxchg(&huge_zero_pfn, 0, page_to_pfn(zero_page))) {
> + __free_page(zero_page);
> + goto retry;
> + }
This might break if preemption can happen here ?
The second thread might loop forever because huge_zero_refcount is 0,
and huge_zero_pfn not zero.
If preemption already disabled, a comment would be nice.
> +
> + /* We take additional reference here. It will be put back by shinker */
typo : shrinker
> + atomic_set(&huge_zero_refcount, 2);
> + return ACCESS_ONCE(huge_zero_pfn);
> +}
> +
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next prev parent reply other threads:[~2012-09-10 14:02 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-10 13:13 [PATCH v2 00/10] Introduce " Kirill A. Shutemov
2012-09-10 13:13 ` [PATCH v2 01/10] thp: huge zero page: basic preparation Kirill A. Shutemov
2012-09-10 13:13 ` [PATCH v2 02/10] thp: zap_huge_pmd(): zap huge zero pmd Kirill A. Shutemov
2012-09-10 13:13 ` [PATCH v2 03/10] thp: copy_huge_pmd(): copy huge zero page Kirill A. Shutemov
2012-09-10 13:13 ` [PATCH v2 04/10] thp: do_huge_pmd_wp_page(): handle " Kirill A. Shutemov
2012-09-10 13:13 ` [PATCH v2 05/10] thp: change_huge_pmd(): keep huge zero page write-protected Kirill A. Shutemov
2012-09-10 13:13 ` [PATCH v2 06/10] thp: change split_huge_page_pmd() interface Kirill A. Shutemov
2012-09-10 13:13 ` [PATCH v2 07/10] thp: implement splitting pmd for huge zero page Kirill A. Shutemov
2012-09-10 13:13 ` [PATCH v2 08/10] thp: setup huge zero page on non-write page fault Kirill A. Shutemov
2012-09-10 13:13 ` [PATCH v2 09/10] thp: lazy huge zero page allocation Kirill A. Shutemov
2012-09-10 13:13 ` [PATCH v2 10/10] thp: implement refcounting for huge zero page Kirill A. Shutemov
2012-09-10 14:02 ` Eric Dumazet [this message]
2012-09-10 14:44 ` Kirill A. Shutemov
2012-09-10 14:48 ` Eric Dumazet
2012-09-10 14:50 ` Kirill A. Shutemov
2012-09-10 14:57 ` Eric Dumazet
2012-09-10 15:07 ` Kirill A. Shutemov
2012-09-12 10:07 ` [PATCH v3 " Kirill A. Shutemov
2012-09-13 17:16 ` Andrea Arcangeli
2012-09-13 17:37 ` Kirill A. Shutemov
2012-09-13 21:17 ` Andrea Arcangeli
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