From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx160.postini.com [74.125.245.160]) by kanga.kvack.org (Postfix) with SMTP id 3D7D46B006C for ; Mon, 2 Jul 2012 23:25:02 -0400 (EDT) Received: by vcbfl10 with SMTP id fl10so4899789vcb.14 for ; Mon, 02 Jul 2012 20:25:01 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <4FF25EFA.1080004@huawei.com> References: <1341047274-5616-1-git-send-email-jiang.liu@huawei.com> <4FF100F0.9050501@huawei.com> <4FF25EFA.1080004@huawei.com> Date: Mon, 2 Jul 2012 20:25:00 -0700 Message-ID: Subject: Re: [PATCH] mm: setup pageblock_order before it's used by sparse From: Yinghai Lu Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Jiang Liu , Benjamin Herrenschmidt Cc: Andrew Morton , Mel Gorman , Tony Luck , Xishi Qiu , KAMEZAWA Hiroyuki , KOSAKI Motohiro , David Rientjes , Minchan Kim , Keping Chen , linux-mm@kvack.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org, Jiang Liu , David Gibson , linuxppc-dev@lists.ozlabs.org On Mon, Jul 2, 2012 at 7:54 PM, Jiang Liu wrote: > On 2012-7-3 4:43, Yinghai Lu wrote: >> On Sun, Jul 1, 2012 at 7:01 PM, Jiang Liu wrote: >>> Hi Yinghai, >>> The patch fails compilation as below: >>> mm/page_alloc.c:151: error: initializer element is not constant >>> mm/page_alloc.c:151: error: expected =91,=92 or =91;=92 before =91__att= ribute__=92 >>> >>> On IA64, HUGETLB_PAGE_ORDER has dependency on variable hpage_shift. >>> # define HUGETLB_PAGE_ORDER (HPAGE_SHIFT - PAGE_SHIFT) >>> # define HPAGE_SHIFT hpage_shift >>> >>> And hpage_shift could be changed by early parameter "hugepagesz". >>> So seems will still need to keep function set_pageblock_order(). >> >> ah, then use use _DEFAULT instead and later could update that in earlyp= aram. >> >> So attached -v2 should work. > Hi Yinghai, > > I'm afraid the v2 will break powerpc. Currently only IA64 and PowerPC > supports variable hugetlb size. > > HPAGE_SHIFT is a variable default to 0 on powerpc. But seems PowerPC > is doing something wrong here, according to it's mm initialization > sequence as below: > start_kernel() > setup_arch() > paging_init() > free_area_init_node() > set_pageblock_order() > refer to HPAGE_SHIFT (still 0) > init_rest() > do_initcalls() > hugetlbpage_init() > setup HPAGE_SHIFT > That means pageblock_order is always set to "MAX_ORDER - 1", not sure > whether this is intended. And it has the same issue as IA64 of wasting > memory if CONFIG_SPARSE is enabled. adding BenH, need to know if it is powerpc intended. > > So it would be better to keep function set_pageblock_order(), it will > fix the memory wasting on both IA64 and PowerPC. Should setup pageblock_order as early as possible to avoid confusing. Thanks Yinghai -- 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/ . Don't email: email@kvack.org