From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3s8M452w9czDqRR for ; Wed, 10 Aug 2016 16:41:09 +1000 (AEST) Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.11/8.16.0.11) with SMTP id u7A6d4Ve027933 for ; Wed, 10 Aug 2016 02:41:06 -0400 Received: from e23smtp07.au.ibm.com (e23smtp07.au.ibm.com [202.81.31.140]) by mx0b-001b2d01.pphosted.com with ESMTP id 24qm9q6de5-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 10 Aug 2016 02:41:06 -0400 Received: from localhost by e23smtp07.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 10 Aug 2016 16:41:03 +1000 Received: from d23relay09.au.ibm.com (d23relay09.au.ibm.com [9.185.63.181]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id 4162D3578052 for ; Wed, 10 Aug 2016 16:41:01 +1000 (EST) Received: from d23av06.au.ibm.com (d23av06.au.ibm.com [9.190.235.151]) by d23relay09.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u7A6f1cQ15335646 for ; Wed, 10 Aug 2016 16:41:01 +1000 Received: from d23av06.au.ibm.com (localhost [127.0.0.1]) by d23av06.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u7A6excM011898 for ; Wed, 10 Aug 2016 16:41:00 +1000 Date: Wed, 10 Aug 2016 12:10:56 +0530 From: Srikar Dronamraju To: Michael Ellerman Cc: Mel Gorman , linux-mm@kvack.org, Vlastimil Babka , Michal Hocko , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Mahesh Salgaonkar , Hari Bathini , Dave Hansen , Balbir Singh Subject: Re: [PATCH] fadump: Register the memory reserved by fadump Reply-To: Srikar Dronamraju References: <1470318165-2521-1-git-send-email-srikar@linux.vnet.ibm.com> <87mvkritii.fsf@concordia.ellerman.id.au> <20160805072838.GF11268@linux.vnet.ibm.com> <87h9azin4g.fsf@concordia.ellerman.id.au> <20160805100609.GP2799@techsingularity.net> <87d1lhtb3s.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <87d1lhtb3s.fsf@concordia.ellerman.id.au> Message-Id: <20160810064056.GB24800@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , > > > Conceptually it would be cleaner, if expensive, to calculate the real > > memblock reserves if HASH_EARLY and ditch the dma_reserve, memory_reserve > > and nr_kernel_pages entirely. > > Why is it expensive? memblock tracks the totals for all memory and > reserved memory AFAIK, so it should just be a case of subtracting one > from the other? Are you suggesting that we use something like memblock_phys_mem_size() but one which returns memblock.reserved.total_size ? Maybe a new function like memblock_reserved_mem_size()? > > > Unfortuantely, aside from the calculation, > > there is a potential cost due to a smaller hash table that affects everyone, > > not just ppc64. > > Yeah OK. We could make it an arch hook, or controlled by a CONFIG. If its based on memblock.reserved.total_size, then should it be arch specific? > > > However, if the hash table is meant to be sized on the > > number of available pages then it really should be based on that and not > > just a made-up number. > > Yeah that seems to make sense. > > The one complication I think is that we may have memory that's marked > reserved in memblock, but is later freed to the page allocator (eg. > initrd). Yes, this is a possibility, for example lets say we want fadump to continue to run instead of rebooting to a new kernel as it does today. > > I'm not sure if that's actually a concern in practice given the relative > size of the initrd and memory on most systems. But possibly there are > other things that get reserved and then freed which could skew the hash > table size calculation. > -- Thanks and Regards Srikar Dronamraju