From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3rfFys41dYzDqsp for ; Wed, 29 Jun 2016 05:21:09 +1000 (AEST) Date: Tue, 28 Jun 2016 15:20:55 -0400 From: Dave Young To: Thiago Jung Bauermann Cc: linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, vgoyal@redhat.com, Eric Biederman Subject: Re: [PATCH v3 3/9] kexec_file: Factor out kexec_locate_mem_hole from kexec_add_buffer. Message-ID: <20160628192055.GA3165@dhcp-128-65.nay.redhat.com> References: <1466538521-31216-1-git-send-email-bauerman@linux.vnet.ibm.com> <4923900.bfxGnX6mM2@hactar> <20160627161948.GA5876@dhcp-128-65.nay.redhat.com> <5428891.iJNV8CI1We@hactar> <20160627202125.GA9230@dhcp-128-65.nay.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20160627202125.GA9230@dhcp-128-65.nay.redhat.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 06/27/16 at 04:21pm, Dave Young wrote: > Please ignore previous reply, I mistakenly send a broken mail without > subject, sorry about it. Resend the reply here. > > On 06/27/16 at 01:37pm, Thiago Jung Bauermann wrote: > > Am Dienstag, 28 Juni 2016, 00:19:48 schrieb Dave Young: > > > On 06/23/16 at 12:37pm, Thiago Jung Bauermann wrote: > > > > Am Donnerstag, 23 Juni 2016, 01:44:07 schrieb Dave Young: > > > > What is bad about the description of top_down? > > > It is not clear enough to me, I personally think the original one in > > > source code is better: > > > /* allocate from top of memory hole */ > > > > Actually I realized there's some discrepancy in how the x86 code uses > > top_down and how I need it to work in powerpc. This may be what is confusing > > about my comment and the existing comment. > > > > x86 always walks memory from bottom to top but if top_down is true, in each > > memory region it will allocate the memory hole in the highest address within > > that region. I don't know why it is done that way, though. > > I think we did not meaning to do this, considering kdump we have only > one crashkernel region for searching (crashk_res) so it is fine. > For kexec maybe changing the walking function to accept top_down is > reasonable. > > Ccing Vivek see if he can remember something.. > > > > > On powerpc, the memory walk itself should be from top to bottom, as well as > > the memory hole allocation within each memory region. What is the particular reason in powerpc for a mandatory top to bottom walking? > > > > Should I add a separate top_down argument to kexec_locate_mem_hole to > > control if the memory walk should be from top to bottom, and then the > > bottom_up member of struct kexec_buf controls where inside each memory > > region the memory hole will be allocated? Using one argument for both sounds more reasonable than using a separate argument for memory walk.. Thanks Dave