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    SubjectRe: [PATCH v2] memory-hotplug: add sysfs zones_online_to attribute
    On 2014/8/23 6:16, Andrew Morton wrote:
    > On Mon, 18 Aug 2014 11:25:36 +0800 Zhang Zhen <zhenzhang.zhang@huawei.com> wrote:
    >
    >> On 2014/8/16 5:37, Toshi Kani wrote:
    >>> On Wed, 2014-08-13 at 12:10 +0800, Zhang Zhen wrote:
    >>>> Currently memory-hotplug has two limits:
    >>>> 1. If the memory block is in ZONE_NORMAL, you can change it to
    >>>> ZONE_MOVABLE, but this memory block must be adjacent to ZONE_MOVABLE.
    >>>> 2. If the memory block is in ZONE_MOVABLE, you can change it to
    >>>> ZONE_NORMAL, but this memory block must be adjacent to ZONE_NORMAL.
    >>>>
    >>>> With this patch, we can easy to know a memory block can be onlined to
    >>>> which zone, and don't need to know the above two limits.
    >>>>
    >>>> Updated the related Documentation.
    >>>>
    >>>> Change v1 -> v2:
    >>>> - optimize the implementation following Dave Hansen's suggestion
    >>>>
    >>>> Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
    >>>> ---
    >>>> Documentation/ABI/testing/sysfs-devices-memory | 8 ++++
    >>>> Documentation/memory-hotplug.txt | 4 +-
    >>>> drivers/base/memory.c | 62 ++++++++++++++++++++++++++
    >>>> include/linux/memory_hotplug.h | 1 +
    >>>> mm/memory_hotplug.c | 2 +-
    >>>> 5 files changed, 75 insertions(+), 2 deletions(-)
    >>>>
    >>>> diff --git a/Documentation/ABI/testing/sysfs-devices-memory b/Documentation/ABI/testing/sysfs-devices-memory
    >>>> index 7405de2..2b2a1d7 100644
    >>>> --- a/Documentation/ABI/testing/sysfs-devices-memory
    >>>> +++ b/Documentation/ABI/testing/sysfs-devices-memory
    >>>> @@ -61,6 +61,14 @@ Users: hotplug memory remove tools
    >>>> http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils
    >>>>
    >>>>
    >>>> +What: /sys/devices/system/memory/memoryX/zones_online_to
    >>>
    >>> I think this name is a bit confusing. How about "valid_online_types"?
    >>>
    >> Thanks for your suggestion.
    >>
    >> This patch has been added to -mm tree.
    >> If most people think so, i would like to modify the interface name.
    >> If not, let's leave it as it is.
    >
    > Yes, the name could be better. Do we actually need "online" in there?
    > How about "valid_zones"?

    Ok, i will change it to valid_zones.
    >
    > Also, it's not really clear to me why we need this sysfs file at all.
    > Do people really read sysfs files, make onlining decisions and manually
    > type in commands? Or is this stuff all automated? If the latter then
    > the script can take care of all this? For example, attempt to online
    > the memory into the desired zone and report failure if that didn't
    > succeed?

    Just like Dave Hansen says, the scripts should be changed when we add a new
    zone type. And ZONE_MOVABLE may be missed by the scripts writer.
    >
    > IOW, please update the changelog to show
    >
    > a) example output from
    > /sys/devices/system/memory/memoryX/whatever-we-call-it and
    >
    > b) example use-cases which help reviewers understand why this
    > feature will be valuable to users.

    Sorry, this patch has been added to -next tree. I can't modify the changelog.
    >
    > Also, please do address the error which Yasuaki Ishimatsu identified.
    >
    Yeah, i have been waiting for http://ozlabs.org/~akpm/mmots/broken-out/memory-hotplug-add-sysfs-zones_online_to-attribute-fix-2.patch
    added to -mm tree.
    So i can send a patch based on -mm tree to address the error which Yasuaki Ishimatsu identified.
    Otherwise, conflicts may occur.

    Thanks!
    >
    > .
    >




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