From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 541A2C433DF for ; Wed, 29 Jul 2020 14:14:06 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1B2222070B for ; Wed, 29 Jul 2020 14:14:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1B2222070B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AFA8F6B0008; Wed, 29 Jul 2020 10:14:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AAA7F6B000A; Wed, 29 Jul 2020 10:14:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 971056B000C; Wed, 29 Jul 2020 10:14:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0131.hostedemail.com [216.40.44.131]) by kanga.kvack.org (Postfix) with ESMTP id 7F7466B0008 for ; Wed, 29 Jul 2020 10:14:05 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 1C38A180D078E for ; Wed, 29 Jul 2020 14:14:05 +0000 (UTC) X-FDA: 77091307650.10.fish64_2f10a2926f73 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin10.hostedemail.com (Postfix) with ESMTP id 6E7F616A07F for ; Wed, 29 Jul 2020 14:13:22 +0000 (UTC) X-HE-Tag: fish64_2f10a2926f73 X-Filterd-Recvd-Size: 6047 Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by imf11.hostedemail.com (Postfix) with ESMTP for ; Wed, 29 Jul 2020 14:13:21 +0000 (UTC) Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 06TE25Et133130; Wed, 29 Jul 2020 10:13:13 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 32jg248neb-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 29 Jul 2020 10:13:13 -0400 Received: from m0098416.ppops.net (m0098416.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 06TE2IcL134462; Wed, 29 Jul 2020 10:13:12 -0400 Received: from ppma05fra.de.ibm.com (6c.4a.5195.ip4.static.sl-reverse.com [149.81.74.108]) by mx0b-001b2d01.pphosted.com with ESMTP id 32jg248nd0-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 29 Jul 2020 10:13:12 -0400 Received: from pps.filterd (ppma05fra.de.ibm.com [127.0.0.1]) by ppma05fra.de.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 06TE54n7014351; Wed, 29 Jul 2020 14:13:10 GMT Received: from b06avi18626390.portsmouth.uk.ibm.com (b06avi18626390.portsmouth.uk.ibm.com [9.149.26.192]) by ppma05fra.de.ibm.com with ESMTP id 32gcqk34qk-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 29 Jul 2020 14:13:10 +0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 06TEBgMf62128482 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 29 Jul 2020 14:11:42 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BD224AE061; Wed, 29 Jul 2020 14:13:07 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2B073AE056; Wed, 29 Jul 2020 14:12:57 +0000 (GMT) Received: from linux.ibm.com (unknown [9.148.204.160]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Wed, 29 Jul 2020 14:12:57 +0000 (GMT) Date: Wed, 29 Jul 2020 17:12:54 +0300 From: Mike Rapoport To: David Hildenbrand Cc: Justin He , Dan Williams , Vishal Verma , Catalin Marinas , Will Deacon , Greg Kroah-Hartman , "Rafael J. Wysocki" , Dave Jiang , Andrew Morton , Steve Capper , Mark Rutland , Logan Gunthorpe , Anshuman Khandual , Hsin-Yi Wang , Jason Gunthorpe , Dave Hansen , Kees Cook , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-nvdimm@lists.01.org" , "linux-mm@kvack.org" , Wei Yang , Pankaj Gupta , Ira Weiny , Kaly Xin Subject: Re: [RFC PATCH 0/6] decrease unnecessary gap due to pmem kmem alignment Message-ID: <20200729141254.GE3672596@linux.ibm.com> References: <20200729033424.2629-1-justin.he@arm.com> <20200729093150.GC3672596@linux.ibm.com> <20200729130025.GD3672596@linux.ibm.com> <170d7861-4df8-ecaf-dbdd-9e9a4a832f8f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <170d7861-4df8-ecaf-dbdd-9e9a4a832f8f@redhat.com> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-07-29_07:2020-07-29,2020-07-29 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 mlxscore=0 mlxlogscore=550 phishscore=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 spamscore=0 adultscore=0 bulkscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007290091 X-Rspamd-Queue-Id: 6E7F616A07F X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jul 29, 2020 at 03:03:04PM +0200, David Hildenbrand wrote: > On 29.07.20 15:00, Mike Rapoport wrote: > > On Wed, Jul 29, 2020 at 11:35:20AM +0200, David Hildenbrand wrote: > >>> > >>> There is still large gap with ARM64_64K_PAGES, though. > >>> > >>> As for SPARSEMEM without VMEMMAP, are there actual benefits to use it? > >> > >> I was asking myself the same question a while ago and didn't really find > >> a compelling one. > > > > Memory overhead for VMEMMAP is larger, especially for arm64 that knows > > how to free empty parts of the memory map with "classic" SPARSEMEM. > > You mean the hole punching within section memmap? (which is why their > pfn_valid() implementation is special) Yes, arm (both 32 and 64) do this. And for smaller systems with a few memory banks this is very reasonable to trade slight (if any) slowdown in pfn_valid() for several megs of memory. > (I do wonder why that shouldn't work with VMEMMAP, or is it simply not > implemented?) It's not implemented. There was a patch [1] recently to implement this. [1] https://lore.kernel.org/lkml/20200721073203.107862-1-liwei213@huawei.com/ > -- > Thanks, > > David / dhildenb > -- Sincerely yours, Mike.