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Thu, 10 Sep 2020 08:49:33 -0400 X-MC-Unique: Yoql_GzKOlSSRvWQJKHr_w-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id F090E10BBECB; Thu, 10 Sep 2020 12:49:31 +0000 (UTC) Received: from [10.36.113.88] (ovpn-113-88.ams2.redhat.com [10.36.113.88]) by smtp.corp.redhat.com (Postfix) with ESMTP id B3A8571775; Thu, 10 Sep 2020 12:49:29 +0000 (UTC) Subject: Re: [PATCH] mm: don't rely on system state to detect hot-plug operations To: Michal Hocko , Oscar Salvador Cc: Laurent Dufour , akpm@linux-foundation.org, rafael@kernel.org, nathanl@linux.ibm.com, cheloha@linux.ibm.com, stable@vger.kernel.org, Greg Kroah-Hartman , linux-mm@kvack.org, LKML References: <9faac1ce-c02d-7dbc-f79a-4aaaa5a73d28@linux.ibm.com> <20200909090953.GE7348@dhcp22.suse.cz> <4cdb54be-1a92-4ba4-6fee-3b415f3468a9@linux.ibm.com> <20200909105914.GF7348@dhcp22.suse.cz> <74a62b00-235e-7deb-2814-f3b240fea25e@linux.ibm.com> <20200910072331.GB28354@dhcp22.suse.cz> <31cfdf35-618f-6f56-ef16-0d999682ad02@linux.ibm.com> <20200910111246.GE28354@dhcp22.suse.cz> <20200910120343.GA6635@linux> <20200910124755.GG28354@dhcp22.suse.cz> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200910124755.GG28354@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Rspamd-Queue-Id: 84FF33D668 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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 10.09.20 14:47, Michal Hocko wrote: > On Thu 10-09-20 14:03:48, Oscar Salvador wrote: >> On Thu, Sep 10, 2020 at 01:35:32PM +0200, Laurent Dufour wrote: >> >>> That points has been raised by David, quoting him here: >>> >>>> IIRC, ACPI can hotadd memory while SCHEDULING, this patch would break that. >>>> >>>> Ccing Oscar, I think he mentioned recently that this is the case with ACPI. >>> >>> Oscar told that he need to investigate further on that. >> >> I think my reply got lost. >> >> We can see acpi hotplugs during SYSTEM_SCHEDULING: >> >> $QEMU -enable-kvm -machine pc -smp 4,sockets=4,cores=1,threads=1 -cpu host -monitor pty \ >> -m size=$MEM,slots=255,maxmem=4294967296k \ >> -numa node,nodeid=0,cpus=0-3,mem=512 -numa node,nodeid=1,mem=512 \ >> -object memory-backend-ram,id=memdimm0,size=134217728 -device pc-dimm,node=0,memdev=memdimm0,id=dimm0,slot=0 \ >> -object memory-backend-ram,id=memdimm1,size=134217728 -device pc-dimm,node=0,memdev=memdimm1,id=dimm1,slot=1 \ >> -object memory-backend-ram,id=memdimm2,size=134217728 -device pc-dimm,node=0,memdev=memdimm2,id=dimm2,slot=2 \ >> -object memory-backend-ram,id=memdimm3,size=134217728 -device pc-dimm,node=0,memdev=memdimm3,id=dimm3,slot=3 \ >> -object memory-backend-ram,id=memdimm4,size=134217728 -device pc-dimm,node=1,memdev=memdimm4,id=dimm4,slot=4 \ >> -object memory-backend-ram,id=memdimm5,size=134217728 -device pc-dimm,node=1,memdev=memdimm5,id=dimm5,slot=5 \ >> -object memory-backend-ram,id=memdimm6,size=134217728 -device pc-dimm,node=1,memdev=memdimm6,id=dimm6,slot=6 \ >> >> kernel: [ 0.753643] __add_memory: nid: 0 start: 0100000000 - 0108000000 (size: 134217728) >> kernel: [ 0.756950] register_mem_sect_under_node: system_state= 1 >> >> kernel: [ 0.760811] register_mem_sect_under_node+0x4f/0x230 >> kernel: [ 0.760811] walk_memory_blocks+0x80/0xc0 >> kernel: [ 0.760811] link_mem_sections+0x32/0x40 >> kernel: [ 0.760811] add_memory_resource+0x148/0x250 >> kernel: [ 0.760811] __add_memory+0x5b/0x90 >> kernel: [ 0.760811] acpi_memory_device_add+0x130/0x300 >> kernel: [ 0.760811] acpi_bus_attach+0x13c/0x1c0 >> kernel: [ 0.760811] acpi_bus_attach+0x60/0x1c0 >> kernel: [ 0.760811] acpi_bus_scan+0x33/0x70 >> kernel: [ 0.760811] acpi_scan_init+0xea/0x21b >> kernel: [ 0.760811] acpi_init+0x2f1/0x33c >> kernel: [ 0.760811] do_one_initcall+0x46/0x1f4 > > Is there any actual usecase for a configuration like this? What is the > point to statically define additional memory like this when the same can > be achieved on the same command line? You can online it movable right away to unplug later. Also, under QEMU, just do a reboot with hotplugged memory and you're in the very same situation. -- Thanks, David / dhildenb