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From: Randy Dunlap <rdunlap@infradead.org>
To: yulei.kernel@gmail.com, linux-mm@kvack.org,
	akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	naoya.horiguchi@nec.com, viro@zeniv.linux.org.uk,
	pbonzini@redhat.com
Cc: joao.m.martins@oracle.com, sean.j.christopherson@intel.com,
	xiaoguangrong.eric@gmail.com, kernellwp@gmail.com,
	lihaiwei.kernel@gmail.com, Yulei Zhang <yuleixzhang@tencent.com>
Subject: Re: [RFC V2 37/37] Add documentation for dmemfs
Date: Thu, 24 Dec 2020 10:27:28 -0800	[thread overview]
Message-ID: <a8920d25-e109-cfce-5137-1f4374c815e9@infradead.org> (raw)
In-Reply-To: <6a3a71f75dad1fa440677fc1bcdc170f178be1d8.1607332046.git.yuleixzhang@tencent.com>

Hi,

On 12/7/20 3:31 AM, yulei.kernel@gmail.com wrote:
> From: Yulei Zhang <yuleixzhang@tencent.com>
> 
> Introduce dmemfs.rst to document the basic usage of dmemfs.
> 
> Signed-off-by: Yulei Zhang <yuleixzhang@tencent.com>
> ---
>  Documentation/filesystems/dmemfs.rst | 58 ++++++++++++++++++++++++++++++++++++
>  Documentation/filesystems/index.rst  |  1 +
>  2 files changed, 59 insertions(+)
>  create mode 100644 Documentation/filesystems/dmemfs.rst
> 
> diff --git a/Documentation/filesystems/dmemfs.rst b/Documentation/filesystems/dmemfs.rst
> new file mode 100644
> index 00000000..f13ed0c
> --- /dev/null
> +++ b/Documentation/filesystems/dmemfs.rst
> @@ -0,0 +1,58 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +=====================================
> +The Direct Memory Filesystem - DMEMFS
> +=====================================
> +
> +
> +.. Table of contents
> +
> +   - Overview
> +   - Compilation
> +   - Usage
> +
> +Overview
> +========
> +
> +Dmemfs (Direct Memory filesystem) is device memory or reserved
> +memory based filesystem. This kind of memory is special as it
> +is not managed by kernel and it is without 'struct page'. Therefore
> +it can save extra memory from the host system for various usage,

                                                             usages,
or                                                           uses,

> +especially for guest virtual machines.
> +
> +It uses a kernel boot parameter ``dmem=`` to reserve the system
> +memory when the host system boots up, the details can be checked

                               boots up. The detail

> +in /Documentation/admin-guide/kernel-parameters.txt.
> +
> +Compilation
> +===========
> +
> +The filesystem should be enabled by turning on the kernel configuration
> +options::
> +
> +        CONFIG_DMEM_FS          - Direct Memory filesystem support
> +        CONFIG_DMEM             - Allow reservation of memory for dmem

Would anyone want DMEM_FS without DMEM?

> +
> +
> +Additionally, the following can be turned on to aid debugging::
> +
> +        CONFIG_DMEM_DEBUG_FS    - Enable debug information for dmem
> +
> +Usage
> +========
> +
> +Dmemfs supports mapping ``4K``, ``2M`` and ``1G`` size of pages to

                                                     sizes

> +the userspace, for example ::

       userspace. For example::

> +
> +    # mount -t dmemfs none -o pagesize=4K /mnt/
> +
> +The it can create the backing storage with 4G size ::

   Then

> +
> +    # truncate /mnt/dmemfs-uuid --size 4G
> +
> +To use as backing storage for virtual machine starts with qemu, just need

                                                 started with qemu, just specify
   the memory-backed-file

> +to specify the memory-backed-file in the qemu command line like this ::
> +
> +    # -object memory-backend-file,id=ram-node0,mem-path=/mnt/dmemfs-uuid \

                        backed


> +        share=yes,size=4G,host-nodes=0,policy=preferred -numa node,nodeid=0,memdev=ram-node0
> +


-- 
~Randy


  reply	other threads:[~2020-12-24 18:29 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-07 11:30 [RFC V2 00/37] Enhance memory utilization with DMEMFS yulei.kernel
2020-12-07 11:30 ` [RFC V2 01/37] fs: introduce dmemfs module yulei.kernel
2020-12-07 14:29   ` kernel test robot
2020-12-07 11:30 ` [RFC V2 02/37] mm: support direct memory reservation yulei.kernel
2020-12-07 11:30 ` [RFC V2 03/37] dmem: implement dmem memory management yulei.kernel
2020-12-07 11:30 ` [RFC V2 04/37] dmem: let pat recognize dmem yulei.kernel
2020-12-07 11:30 ` [RFC V2 05/37] dmemfs: support mmap for dmemfs yulei.kernel
2020-12-07 14:51   ` kernel test robot
2020-12-07 11:30 ` [RFC V2 06/37] dmemfs: support truncating inode down yulei.kernel
2020-12-07 11:31 ` [RFC V2 07/37] dmem: trace core functions yulei.kernel
2020-12-07 11:31 ` [RFC V2 08/37] dmem: show some statistic in debugfs yulei.kernel
2020-12-07 11:31 ` [RFC V2 09/37] dmemfs: support remote access yulei.kernel
2020-12-07 11:31 ` [RFC V2 10/37] dmemfs: introduce max_alloc_try_dpages parameter yulei.kernel
2020-12-07 11:31 ` [RFC V2 11/37] mm: export mempolicy interfaces to serve dmem allocator yulei.kernel
2020-12-07 11:31 ` [RFC V2 12/37] dmem: introduce mempolicy support yulei.kernel
2020-12-07 11:31 ` [RFC V2 13/37] mm, dmem: introduce PFN_DMEM and pfn_t_dmem yulei.kernel
2020-12-07 11:31 ` [RFC V2 14/37] mm, dmem: differentiate dmem-pmd and thp-pmd yulei.kernel
2020-12-07 11:31 ` [RFC V2 15/37] mm: add pmd_special() check for pmd_trans_huge_lock() yulei.kernel
2020-12-07 11:31 ` [RFC V2 16/37] dmemfs: introduce ->split() to dmemfs_vm_ops yulei.kernel
2020-12-07 11:31 ` [RFC V2 17/37] mm, dmemfs: support unmap_page_range() for dmemfs pmd yulei.kernel
2020-12-07 11:31 ` [RFC V2 18/37] mm: follow_pmd_mask() for dmem huge pmd yulei.kernel
2020-12-07 11:31 ` [RFC V2 19/37] mm: gup_huge_pmd() " yulei.kernel
2020-12-07 11:31 ` [RFC V2 20/37] mm: support dmem huge pmd for vmf_insert_pfn_pmd() yulei.kernel
2020-12-07 11:31 ` [RFC V2 21/37] mm: support dmem huge pmd for follow_pfn() yulei.kernel
2020-12-07 11:31 ` [RFC V2 22/37] kvm, x86: Distinguish dmemfs page from mmio page yulei.kernel
2020-12-07 11:31 ` [RFC V2 23/37] kvm, x86: introduce VM_DMEM for syscall support usage yulei.kernel
2020-12-07 15:25   ` kernel test robot
2020-12-07 11:31 ` [RFC V2 24/37] dmemfs: support hugepage for dmemfs yulei.kernel
2020-12-07 11:31 ` [RFC V2 25/37] mm, x86, dmem: fix estimation of reserved page for vaddr_get_pfn() yulei.kernel
2020-12-07 11:31 ` [RFC V2 26/37] mm, dmem: introduce pud_special() for dmem huge pud support yulei.kernel
2020-12-07 11:31 ` [RFC V2 27/37] mm: add pud_special() check to support dmem huge pud yulei.kernel
2020-12-07 11:31 ` [RFC V2 28/37] mm, dmemfs: support huge_fault() for dmemfs yulei.kernel
2020-12-07 11:31 ` [RFC V2 29/37] mm: add follow_pte_pud() to support huge pud look up yulei.kernel
2020-12-07 11:31 ` [RFC V2 30/37] dmem: introduce dmem_bitmap_alloc() and dmem_bitmap_free() yulei.kernel
2020-12-07 11:31 ` [RFC V2 31/37] dmem: introduce mce handler yulei.kernel
2020-12-07 11:31 ` [RFC V2 32/37] mm, dmemfs: register and handle the dmem mce yulei.kernel
2020-12-07 15:35   ` kernel test robot
2020-12-07 11:31 ` [RFC V2 33/37] kvm, x86: enable record_steal_time for dmem yulei.kernel
2020-12-07 11:31 ` [RFC V2 34/37] dmem: add dmem unit tests yulei.kernel
2020-12-07 11:31 ` [RFC V2 35/37] mm, dmem: introduce dregion->memmap for dmem yulei.kernel
2020-12-07 17:25   ` kernel test robot
2020-12-07 11:31 ` [RFC V2 36/37] vfio: support dmempage refcount for vfio yulei.kernel
2020-12-07 14:29   ` kernel test robot
2020-12-07 17:38   ` kernel test robot
2020-12-07 11:31 ` [RFC V2 37/37] Add documentation for dmemfs yulei.kernel
2020-12-24 18:27   ` Randy Dunlap [this message]
2020-12-07 12:02 ` [RFC V2 00/37] Enhance memory utilization with DMEMFS David Hildenbrand
2020-12-07 19:32   ` Dan Williams
2020-12-07 19:32     ` Dan Williams

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