From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 179036B005A for ; Tue, 29 Nov 2011 05:52:42 -0500 (EST) From: Johannes Weiner Subject: [patch 5/7] mm: page_cgroup: check page_cgroup arrays in lookup_page_cgroup() only when necessary Date: Tue, 29 Nov 2011 11:52:03 +0100 Message-Id: <1322563925-1667-6-git-send-email-hannes@cmpxchg.org> In-Reply-To: <1322563925-1667-1-git-send-email-hannes@cmpxchg.org> References: <1322563925-1667-1-git-send-email-hannes@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: KAMEZAWA Hiroyuki , Michal Hocko , Balbir Singh , David Rientjes , Hugh Dickins , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org lookup_page_cgroup() is usually used only against pages that are used in userspace. The exception is the CONFIG_DEBUG_VM-only memcg check from the page allocator: it can run on pages without page_cgroup descriptors allocated when the pages are fed into the page allocator for the first time during boot or memory hotplug. Include the array check only when CONFIG_DEBUG_VM is set and save the unnecessary check in production kernels. Signed-off-by: Johannes Weiner --- mm/page_cgroup.c | 18 ++++++++++++++++-- 1 files changed, 16 insertions(+), 2 deletions(-) diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c index a14655d..58405ca 100644 --- a/mm/page_cgroup.c +++ b/mm/page_cgroup.c @@ -28,9 +28,16 @@ struct page_cgroup *lookup_page_cgroup(struct page *page) struct page_cgroup *base; base = NODE_DATA(page_to_nid(page))->node_page_cgroup; +#ifdef CONFIG_DEBUG_VM + /* + * The sanity checks the page allocator does upon freeing a + * page can reach here before the page_cgroup arrays are + * allocated when feeding a range of pages to the allocator + * for the first time during bootup or memory hotplug. + */ if (unlikely(!base)) return NULL; - +#endif offset = pfn - NODE_DATA(page_to_nid(page))->node_start_pfn; return base + offset; } @@ -87,9 +94,16 @@ struct page_cgroup *lookup_page_cgroup(struct page *page) { unsigned long pfn = page_to_pfn(page); struct mem_section *section = __pfn_to_section(pfn); - +#ifdef CONFIG_DEBUG_VM + /* + * The sanity checks the page allocator does upon freeing a + * page can reach here before the page_cgroup arrays are + * allocated when feeding a range of pages to the allocator + * for the first time during bootup or memory hotplug. + */ if (!section->page_cgroup) return NULL; +#endif return section->page_cgroup + pfn; } -- 1.7.6.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org