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[91.12.99.101]) by smtp.gmail.com with ESMTPSA id v189sm12118531wmg.9.2021.04.23.03.35.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 23 Apr 2021 03:35:36 -0700 (PDT) Subject: Re: [PATCH v6 00/15] RAM_NORESERVE, MAP_NORESERVE and hostmem "reserve" property To: Eduardo Habkost , Paolo Bonzini References: <20210421122624.12292-1-david@redhat.com> <20210421210611.wradfrdrbw6ebcdn@habkost.net> From: David Hildenbrand Organization: Red Hat Message-ID: Date: Fri, 23 Apr 2021 12:35:35 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210421210611.wradfrdrbw6ebcdn@habkost.net> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marcel Apfelbaum , "Michael S. Tsirkin" , Richard Henderson , "Dr. David Alan Gilbert" , Peter Xu , qemu-devel@nongnu.org, Greg Kurz , Stefan Hajnoczi , Murilo Opsfelder Araujo , Igor Mammedov , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 21.04.21 23:06, Eduardo Habkost wrote: > On Wed, Apr 21, 2021 at 02:26:09PM +0200, David Hildenbrand wrote: >> Based-on: 20210406080126.24010-1-david@redhat.com >> >> Some cleanups previously sent in other context (resizeable allocations), >> followed by RAM_NORESERVE, implementing it under Linux using MAP_NORESERVE, >> and letting users configure it for memory backens using the "reserve" >> property (default: true). >> >> MAP_NORESERVE under Linux has in the context of QEMU an effect on >> 1) Private/shared anonymous memory >> -> memory-backend-ram,id=mem0,size=10G >> 2) Private fd-based mappings >> -> memory-backend-file,id=mem0,size=10G,mem-path=/dev/shm/0 >> -> memory-backend-memfd,id=mem0,size=10G >> 3) Private/shared hugetlb mappings >> -> memory-backend-memfd,id=mem0,size=10G,hugetlb=on,hugetlbsize=2M >> >> With MAP_NORESERVE/"reserve=off", we won't be reserving swap space (1/2) or >> huge pages (3) for the whole memory region. >> >> The target use case is virtio-mem, which dynamically exposes memory >> inside a large, sparse memory area to the VM. MAP_NORESERVE tells the OS >> "this mapping might be very sparse". This essentially allows >> avoiding having to set "/proc/sys/vm/overcommit_memory == 1") when using >> virtio-mem and also supporting hugetlbfs in the future. > > For the memory backend and machine core code: > > Acked-by: Eduardo Habkost > Thanks Eduardo. I assume Paolo will be the right maintainer to pick this up? (I hope he'll have time to look at this and some of my pending-for-a-long-time series soon :( ) -- Thanks, David / dhildenb