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From: "Zhijian Li (Fujitsu)" <lizhijian@fujitsu.com>
To: Vishal Verma <vishal.l.verma@intel.com>,
	Dave Jiang <dave.jiang@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"nvdimm@lists.linux.dev" <nvdimm@lists.linux.dev>,
	"linux-cxl@vger.kernel.org" <linux-cxl@vger.kernel.org>,
	David Hildenbrand <david@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Huang Ying <ying.huang@intel.com>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>
Subject: Re: [PATCH v2 2/2] dax: add a sysfs knob to control memmap_on_memory behavior
Date: Thu, 7 Dec 2023 08:29:56 +0000	[thread overview]
Message-ID: <4b1a415e-6a56-455a-a843-277cc08d05a9@fujitsu.com> (raw)
In-Reply-To: <20231206-vv-dax_abi-v2-2-f4f4f2336d08@intel.com>

Hi Vishal,


On 07/12/2023 12:36, Vishal Verma wrote:
> +
> +What:		/sys/bus/dax/devices/daxX.Y/memmap_on_memory
> +Date:		October, 2023
> +KernelVersion:	v6.8
> +Contact:	nvdimm@lists.linux.dev
> +Description:
> +		(RW) Control the memmap_on_memory setting if the dax device
> +		were to be hotplugged as system memory. This determines whether
> +		the 'altmap' for the hotplugged memory will be placed on the
> +		device being hotplugged (memmap_on+memory=1) or if it will be

s/memmap_on+memory=1/memmap_on_memory=1


I have a question here

What relationship about memmap_on_memory and 'ndctl-create-namespace -M' option which
specifies where is the vmemmap backed memory.
I'm confused that memmap_on_memory=1 and '-M dev' are the same for nvdimm devdax mode ?

ndctl-create-namespace
...
        -M, --map=
            A pmem namespace in "fsdax" or "devdax" mode requires allocation of per-page metadata. The allocation
            can be drawn from either:

            •   "mem": typical system memory

            •   "dev": persistent memory reserved from the namespace :: Given relative capacities of "Persistent
                Memory" to "System RAM" the allocation defaults to reserving space out of the namespace directly
                ("--map=dev"). The overhead is 64-bytes per 4K (16GB per 1TB) on x86.


Thanks
Zhijian

> +		placed on regular memory (memmap_on_memory=0). This attribute
> +		must be set before the device is handed over to the 'kmem'

next prev parent reply	other threads:[~2023-12-07  8:30 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-12-07  4:36 [PATCH v2 0/2] Add DAX ABI for memmap_on_memory Vishal Verma
2023-12-07  4:36 ` [PATCH v2 1/2] Documentatiion/ABI: Add ABI documentation for sys-bus-dax Vishal Verma
2023-12-07  4:36 ` [PATCH v2 2/2] dax: add a sysfs knob to control memmap_on_memory behavior Vishal Verma
2023-12-07  8:29   ` Zhijian Li (Fujitsu) [this message]
2023-12-07 19:25     ` Verma, Vishal L
2023-12-08  9:20       ` Zhijian Li (Fujitsu)
2023-12-08 21:24         ` Verma, Vishal L
2023-12-08  3:13   ` Huang, Ying
2023-12-08 21:25     ` Verma, Vishal L
2023-12-08 11:36   ` David Hildenbrand
2023-12-08 21:26     ` Verma, Vishal L

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