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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id c19-v6sm23082198wre.86.2018.09.19.05.17.21 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 19 Sep 2018 05:17:22 -0700 (PDT) Date: Wed, 19 Sep 2018 14:17:20 +0200 From: Ingo Molnar To: Masayoshi Mizuma Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Baoquan He , Masayoshi Mizuma , linux-kernel@vger.kernel.org, mike.travis@hpe.com, sivanich@hpe.com Subject: Re: [PATCH v3 1/2] x86/mm: Add an option to change the padding used for the physical memory mapping Message-ID: <20180919121720.GA47424@gmail.com> References: <20180904151141.20264-1-msys.mizuma@gmail.com> <20180918133026.gzyix3oyrfcsrdcx@gabell> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180918133026.gzyix3oyrfcsrdcx@gabell> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Masayoshi Mizuma wrote: > Ping... > I would appreciate if someone could review it because this patch > fixes the real memory hotplug issue... Yeah, so I generally try to resist random new boot options that work around real bugs, so please convince me that this patch is the best option: > > On Tue, Sep 04, 2018 at 11:11:40AM -0400, Masayoshi Mizuma wrote: > > From: Masayoshi Mizuma > > > > If each node of physical memory layout has huge space for hotplug, > > the padding used for the physical memory mapping section is not enough. > > For exapmle of the layout: > > SRAT: Node 6 PXM 4 [mem 0x100000000000-0x13ffffffffff] hotplug > > SRAT: Node 7 PXM 5 [mem 0x140000000000-0x17ffffffffff] hotplug > > SRAT: Node 2 PXM 6 [mem 0x180000000000-0x1bffffffffff] hotplug > > SRAT: Node 3 PXM 7 [mem 0x1c0000000000-0x1fffffffffff] hotplug > > > > We can increase the padding by CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING, > > however, the needed padding size depends on the system environment. > > The kernel option is better than changing the config. > > > > Change log from v2: > > - Simplify the description. As Baoquan said, this is simillar SGI UV issue, > > but a little different. Remove SGI UV description. Could you please explain it a bit better where the higher padding requirement comes from? 'system environment' is very opaque. Thanks, Ingo