From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id 27F9D8D003A for ; Thu, 20 Jan 2011 12:52:37 -0500 (EST) Received: by ywj3 with SMTP id 3so284504ywj.14 for ; Thu, 20 Jan 2011 09:52:34 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <1295516739-9839-1-git-send-email-pullip.cho@samsung.com> <20110120142844.GA28358@barrios-desktop> Date: Fri, 21 Jan 2011 02:52:34 +0900 Message-ID: Subject: Re: [PATCH] ARM: mm: Regarding section when dealing with meminfo From: KyongHo Cho Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org, Kukjin Kim , Ilho Lee , KeyYoung Park , KyongHo Cho List-ID: On Fri, Jan 21, 2011 at 2:44 AM, Minchan Kim wrote: > Fix linux-arm-kernel address. > Thank you! Too late in the night:) > On Fri, Jan 21, 2011 at 2:43 AM, Minchan Kim wrote: >> Restore Cced. >> >> On Fri, Jan 21, 2011 at 2:24 AM, KyongHo Cho wrote: >>> On Thu, Jan 20, 2011 at 11:28 PM, Minchan Kim wrote: >>>> On Thu, Jan 20, 2011 at 06:45:39PM +0900, KyongHo Cho wrote: >>>>> Sparsemem allows that a bank of memory spans over several adjacent >>>>> sections if the start address and the end address of the bank >>>>> belong to different sections. >>>>> When gathering statictics of physical memory in mem_init() and >>>>> show_mem(), this possiblity was not considered. >>>> >>>> Please write down the result if we doesn't consider this patch. >>>> I can understand what happens but for making good description and review, >>>> merging easily, it would be better to write down the result without >>>> the patch explicitly. >>>> >>> As we know that each section has its own memmap and >>> a contiguous chunk of physical memory that is represented by 'bank' in meminfo >>> can be larger than the size of a section. >>> "page++" in the current implementation can access invalid memory area. >>> The size of the section is 256 MiB in ARM and the number of banks in >>> meminfo is 8. >>> This means that the maximum size of the physical memory cannot be grow than 2GiB >>> to avoid this problem in the current implementation. >>> Thus we need to fix the calculation of the last page descriptor in >>> terms of sections. >>> >>> This patch determines the last page descriptor in a memmap with >>> min(last_pfn_of_bank, last_pfn_of_current_section) >>> If there remains physical memory not consumed, it calculates the last >>> page descriptor >>> with min(last_pfn_of_bank, last_pfn_of_next_section). >>> >>>> >>>> Hmm.. new ifndef magic makes code readability bad. >>>> Couldn't we do it by simple pfn iterator not page and pfn_valid check? >>>> >>> True. >>> We need to consider the implementation again. >>> I think the previous implementation gave the importance to the >>> efficiency but to the readability. >>> >> >> Please consider readability and consistency with other architectures >> if we can do. :) >> Thanks. >> >> -- >> Kind regards, >> Minchan Kim >> > > > > -- > Kind regards, > Minchan Kim > -- 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 policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org