From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e31.co.us.ibm.com ([32.97.110.149]:33398 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758023Ab2J3PXV (ORCPT ); Tue, 30 Oct 2012 11:23:21 -0400 Received: from /spool/local by e31.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 30 Oct 2012 09:23:16 -0600 Message-ID: <508FEECE.2070402@linux.vnet.ibm.com> Date: Tue, 30 Oct 2012 08:14:22 -0700 From: Dave Hansen MIME-Version: 1.0 Subject: Re: [PATCH] mm: memmap_init_zone() performance improvement References: <1349276174-8398-1-git-send-email-mike.yoknis@hp.com> <20121008151656.GM29125@suse.de> <1349794597.29752.10.camel@MikesLinux.fc.hp.com> <1350676398.1169.6.camel@MikesLinux.fc.hp.com> <20121020082858.GA2698@suse.de> In-Reply-To: <20121020082858.GA2698@suse.de> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Mel Gorman Cc: Mike Yoknis , mingo@redhat.com, akpm@linux-foundation.org, linux-arch@vger.kernel.org, mmarek@suse.cz, tglx@linutronix.de, hpa@zytor.com, arnd@arndb.de, sam@ravnborg.org, minchan@kernel.org, kamezawa.hiroyu@jp.fujitsu.com, mhocko@suse.cz, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org On 10/20/2012 01:29 AM, Mel Gorman wrote: > I'm travelling at the moment so apologies that I have not followed up on > this. My problem is still the same with the patch - it changes more > headers than is necessary and it is sparsemem specific. At minimum, try > the suggestion of > > if (!early_pfn_valid(pfn)) { > pfn = ALIGN(pfn + MAX_ORDER_NR_PAGES, MAX_ORDER_NR_PAGES) - 1; > continue; > } Sorry I didn't catch this until v2... Is that ALIGN() correct? If pfn=3, then it would expand to: (3+MAX_ORDER_NR_PAGES+MAX_ORDER_NR_PAGES-1) & ~(MAX_ORDER_NR_PAGES-1) You would end up skipping the current MAX_ORDER_NR_PAGES area, and then one _extra_ because ALIGN() aligns up, and you're adding MAX_ORDER_NR_PAGES too. It doesn't matter unless you run in to a !early_valid_pfn() in the middle of a MAX_ORDER area, I guess. I think this would work, plus be a bit smaller: pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES) - 1;