From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f44.google.com (mail-pa0-f44.google.com [209.85.220.44]) by kanga.kvack.org (Postfix) with ESMTP id E97586B0037 for ; Wed, 9 Oct 2013 19:30:33 -0400 (EDT) Received: by mail-pa0-f44.google.com with SMTP id lf10so1787823pab.31 for ; Wed, 09 Oct 2013 16:30:33 -0700 (PDT) Received: by mail-pa0-f43.google.com with SMTP id hz1so1780752pad.30 for ; Wed, 09 Oct 2013 16:30:30 -0700 (PDT) Message-ID: <5255E701.9050100@gmail.com> Date: Thu, 10 Oct 2013 07:30:09 +0800 From: Zhang Yanfei MIME-Version: 1.0 Subject: Re: [PATCH part1 v6 4/6] x86/mem-hotplug: Support initialize page tables in bottom-up References: <524E2032.4020106@gmail.com> <524E2127.4090904@gmail.com> <5251F9AB.6000203@zytor.com> <525442A4.9060709@gmail.com> <20131009164449.GG22495@htj.dyndns.org> <52558EEF.4050009@gmail.com> <20131009192040.GA5592@mtj.dyndns.org> <5255C87F.8070701@gmail.com> <5255C91B.7030608@zytor.com> In-Reply-To: <5255C91B.7030608@zytor.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "H. Peter Anvin" Cc: Tejun Heo , Andrew Morton , "Rafael J . Wysocki" , lenb@kernel.org, Thomas Gleixner , mingo@elte.hu, Toshi Kani , Wanpeng Li , Thomas Renninger , Yinghai Lu , Jiang Liu , Wen Congyang , Lai Jiangshan , isimatu.yasuaki@jp.fujitsu.com, izumi.taku@jp.fujitsu.com, Mel Gorman , Minchan Kim , mina86@mina86.com, gong.chen@linux.intel.com, vasilis.liaskovitis@profitbricks.com, lwoodman@redhat.com, Rik van Riel , jweiner@redhat.com, prarit@redhat.com, "x86@kernel.org" , linux-doc@vger.kernel.org, "linux-kernel@vger.kernel.org" , Linux MM , linux-acpi@vger.kernel.org, imtangchen@gmail.com, Zhang Yanfei , Tang Chen On 10/10/2013 05:22 AM, H. Peter Anvin wrote: > On 10/09/2013 02:19 PM, Zhang Yanfei wrote: >>> >>> Yeah, I was referring to the 16MB limit, which apparently ceased to >>> exist. >> >> Hmmmm...If we are talking 16MB limit hear, I don't think it a problem, either. >> Currently, default loading & running address of kernel is 16MB, so the >> kernel itself is above 16MB, memory allocated in bottom-up mode is obviously >> above the 16MB. Just seeing from a RHEL6.3 server: >> >> 01000000-01507ff4 : Kernel code >> 01507ff5-01c07b2f : Kernel data >> 01d4e000-02012023 : Kernel bss >> >> IOW, even if kernel is loaded and running at 1MB, it self will occupy about >> 16MB from the above. >> > > For various DMA devices you can find almost every possible power of 2 > being a limitation. The most common limits are 24, 32, and 40 bits, but > you also see odd ones like 30 bits in the field. Really. > Thanks for this. I was always curious about what the limit is when we said DMA limit before. -- Thanks. Zhang Yanfei -- 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