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From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linuxppc-dev@lists.ozlabs.org, linux-hyperv@vger.kernel.org,
	Wei Yang <richard.weiyang@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Oscar Salvador <osalvador@suse.de>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Baoquan He <bhe@redhat.com>
Subject: Re: [PATCH v2 8/8] mm/memory_hotplug: allow to specify a default online_type
Date: Tue, 17 Mar 2020 12:05:50 +0100	[thread overview]
Message-ID: <04ad4a95-e455-5fa4-01e0-fa2e0416adbb@redhat.com> (raw)
In-Reply-To: <20200317110121.GN26018@dhcp22.suse.cz>

On 17.03.20 12:01, Michal Hocko wrote:
> On Tue 17-03-20 11:49:42, David Hildenbrand wrote:
>> For now, distributions implement advanced udev rules to essentially
>> - Don't online any hotplugged memory (s390x)
>> - Online all memory to ZONE_NORMAL (e.g., most virt environments like
>>   hyperv)
>> - Online all memory to ZONE_MOVABLE in case the zone imbalance is taken
>>   care of (e.g., bare metal, special virt environments)
>>
>> In summary: All memory is usually onlined the same way, however, the
>> kernel always has to ask user space to come up with the same answer.
>> E.g., Hyper-V always waits for a memory block to get onlined before
>> continuing, otherwise it might end up adding memory faster than
>> hotplugging it, which can result in strange OOM situations. This waiting
>> slows down adding of a bigger amount of memory.
>>
>> Let's allow to specify a default online_type, not just "online" and
>> "offline". This allows distributions to configure the default online_type
>> when booting up and be done with it.
>>
>> We can now specify "offline", "online", "online_movable" and
>> "online_kernel" via
>> - "memhp_default_state=" on the kernel cmdline
>> - /sys/devices/system/memory/auto_online_blocks
>> just like we are able to specify for a single memory block via
>> /sys/devices/system/memory/memoryX/state
>>
>> Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Michal Hocko <mhocko@kernel.org>
>> Cc: Oscar Salvador <osalvador@suse.de>
>> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
>> Cc: Baoquan He <bhe@redhat.com>
>> Cc: Wei Yang <richard.weiyang@gmail.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
> 
> As I've said earlier and several times already, I really dislike this
> interface. But it is fact that this patch doesn't make it any worse.
> Quite contrary, so feel free to add
> Acked-by: Michal Hocko <mhocko@suse.com>

Thanks Michal!

-- 
Thanks,

David / dhildenb


  reply	other threads:[~2020-03-17 11:06 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-17 10:49 [PATCH v2 0/8] mm/memory_hotplug: allow to specify a default online_type David Hildenbrand
2020-03-17 10:49 ` [PATCH v2 1/8] drivers/base/memory: rename MMOP_ONLINE_KEEP to MMOP_ONLINE David Hildenbrand
2020-03-17 10:49 ` [PATCH v2 2/8] drivers/base/memory: map MMOP_OFFLINE to 0 David Hildenbrand
2020-03-17 10:49 ` [PATCH v2 3/8] drivers/base/memory: store mapping between MMOP_* and string in an array David Hildenbrand
2020-03-17 10:49 ` [PATCH v2 4/8] powernv/memtrace: always online added memory blocks David Hildenbrand
2020-03-17 10:58   ` Michal Hocko
2020-03-17 22:04   ` Wei Yang
2020-03-19  9:49   ` Michael Ellerman
2020-03-17 10:49 ` [PATCH v2 5/8] hv_balloon: don't check for memhp_auto_online manually David Hildenbrand
2020-03-17 16:29   ` Vitaly Kuznetsov
2020-03-17 16:33     ` David Hildenbrand
2020-03-17 18:46   ` David Hildenbrand
2020-03-17 10:49 ` [PATCH v2 6/8] mm/memory_hotplug: unexport memhp_auto_online David Hildenbrand
2020-03-17 10:59   ` Michal Hocko
2020-03-17 22:24   ` Wei Yang
2020-03-17 10:49 ` [PATCH v2 7/8] mm/memory_hotplug: convert memhp_auto_online to store an online_type David Hildenbrand
2020-03-17 11:00   ` Michal Hocko
2020-03-17 10:49 ` [PATCH v2 8/8] mm/memory_hotplug: allow to specify a default online_type David Hildenbrand
2020-03-17 11:01   ` Michal Hocko
2020-03-17 11:05     ` David Hildenbrand [this message]
2020-03-17 11:08   ` David Hildenbrand
2020-03-18 13:05 ` [PATCH v2 0/8] " Baoquan He
2020-03-18 13:50   ` David Hildenbrand
2020-03-18 14:50     ` Baoquan He
2020-03-18 13:54   ` Michal Hocko
2020-03-18 14:41     ` Baoquan He
2020-03-18 13:58   ` Vitaly Kuznetsov
2020-03-18 14:41     ` Baoquan He
2020-03-18 15:00       ` Vitaly Kuznetsov

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