From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx179.postini.com [74.125.245.179]) by kanga.kvack.org (Postfix) with SMTP id 1C9186B005A for ; Wed, 18 Jul 2012 03:15:55 -0400 (EDT) Message-ID: <1342595730.3669.70.camel@pasglop> Subject: Re: [PATCH] mm: setup pageblock_order before it's used by sparse From: Benjamin Herrenschmidt Date: Wed, 18 Jul 2012 17:15:30 +1000 In-Reply-To: References: <1341047274-5616-1-git-send-email-jiang.liu@huawei.com> <4FF100F0.9050501@huawei.com> <4FF25EFA.1080004@huawei.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Yinghai Lu Cc: Jiang Liu , 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, 2012-07-02 at 20:25 -0700, Yinghai Lu wrote: > > 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. Hrm, HPAGE_SHIFT is initially 0 because we only know at runtime what huge page sizes are going to be supported (if any). The business with pageblock_order is new to me and does look bogus today indeed. But not a huge deal either. Our MAX_ORDER is typically 9 (64K pages) or 13 (4K pages) and our standard huge page size is generally 16M so there isn't a big difference here. Still, maybe something worth looking into... Cheers, Ben. -- 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