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From: Dan Williams <dan.j.williams@intel.com>
To: Vishal Verma <vishal.l.verma@intel.com>
Cc: linux-nvdimm <linux-nvdimm@lists.01.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Ben Olson <ben.olson@intel.com>,
	Michal Biesek <michal.biesek@intel.com>
Subject: Re: [ndctl PATCH 08/10] Documentation: clarify memory movablity for reconfigure-device
Date: Fri, 18 Oct 2019 13:46:54 -0700
Message-ID: <CAPcyv4hHT1fjPirPE8Ex5NZ8_4SjoTj-GNaXP+0+14jNBCHTig@mail.gmail.com> (raw)
In-Reply-To: <20191002234925.9190-9-vishal.l.verma@intel.com>

On Wed, Oct 2, 2019 at 4:49 PM Vishal Verma <vishal.l.verma@intel.com> wrote:
>
> Move the note about potential races in memory onlining into the
> 'Description' section to make it more prominent. Reword the note to talk
> about the sources of such races, and talk about the new 'race detection'
> semantics in daxctl.
>
> Link: https://github.com/pmem/ndctl/issues/110
> Reported-by: Ben Olson <ben.olson@intel.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> ---
>  .../daxctl/daxctl-reconfigure-device.txt      | 24 +++++++++++--------
>  1 file changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/daxctl/daxctl-reconfigure-device.txt b/Documentation/daxctl/daxctl-reconfigure-device.txt
> index 196d692..4663529 100644
> --- a/Documentation/daxctl/daxctl-reconfigure-device.txt
> +++ b/Documentation/daxctl/daxctl-reconfigure-device.txt
> @@ -97,6 +97,20 @@ error reconfiguring devices: Operation not supported
>  reconfigured 0 devices
>  ----
>
> +'daxctl-reconfigure-device' nominally expects that it will online new memory
> +blocks as 'movable', so that kernel data doesn't make it into this memory.
> +However, there are other potential agents that may be configured to
> +automatically online new hot-plugged memory as it appears. Most notably,
> +these are the '/sys/devices/system/memory/auto_online_blocks' configuration,
> +or system udev rules. If such an agent races to online memory sections, daxctl
> +checks if the blocks were onlined as 'movable' memory. If this was not the
> +case, and the memory blocks are found to be in a different zone, then a
> +warning is displayed. If it is desired that a different agent control the
> +onlining of memory blocks, and the associated memory zone, then it is
> +recommended to use the --no-online option described below. This will abridge
> +the device reconfiguration operation to just hotplugging the memory, and
> +refrain from then onlining it.

Oh here's that full description that calls out udev.

I think just "See daxctl reconfigure-device --help" is sufficient for
those warnings in the previous patch.
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Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-02 23:49 [ndctl PATCH 00/10] fixes and movability for system-ram mode Vishal Verma
2019-10-02 23:49 ` [ndctl PATCH 01/10] libdaxctl: refactor path construction in op_for_one_memblock() Vishal Verma
2019-10-18 18:43   ` Dan Williams
2019-10-02 23:49 ` [ndctl PATCH 02/10] libdaxctl: refactor memblock_is_online() checks Vishal Verma
2019-10-18 18:45   ` Dan Williams
2019-10-02 23:49 ` [ndctl PATCH 03/10] daxctl/device.c: fix json output omission for reconfigure-device Vishal Verma
2019-10-18 18:46   ` Dan Williams
2019-10-02 23:49 ` [ndctl PATCH 04/10] libdaxctl: add an API to determine if memory is movable Vishal Verma
2019-10-18 18:54   ` Dan Williams
2019-10-18 19:57     ` Verma, Vishal L
2019-10-18 20:40       ` Dan Williams
2019-10-02 23:49 ` [ndctl PATCH 05/10] libdaxctl: allow memblock_in_dev() to return an error Vishal Verma
2019-10-18 19:15   ` Dan Williams
2019-10-02 23:49 ` [ndctl PATCH 06/10] daxctl: show a 'movable' attribute in device listings Vishal Verma
2019-10-18 19:16   ` Dan Williams
2019-10-02 23:49 ` [ndctl PATCH 07/10] daxctl: detect races when onlining memory blocks Vishal Verma
2019-10-18 19:26   ` Dan Williams
2019-10-02 23:49 ` [ndctl PATCH 08/10] Documentation: clarify memory movablity for reconfigure-device Vishal Verma
2019-10-18 20:46   ` Dan Williams [this message]
2019-10-18 20:50     ` Verma, Vishal L
2019-10-02 23:49 ` [ndctl PATCH 09/10] libdaxctl: add an API to online memory in a non-movable state Vishal Verma
2019-10-18 20:54   ` Dan Williams
2019-10-02 23:49 ` [ndctl PATCH 10/10] daxctl: add --no-movable option for onlining memory Vishal Verma
2019-10-18 20:58   ` Dan Williams
2019-10-18 21:04     ` Verma, Vishal L
2019-10-18 21:25       ` Dan Williams

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