From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
virtio-dev@lists.oasis-open.org,
virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
"Michael S . Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH RFC v4 12/13] mm/vmscan: Export drop_slab() and drop_slab_node()
Date: Tue, 25 Feb 2020 18:23:23 +0100 [thread overview]
Message-ID: <9c21be0c-5eef-58c2-bfb9-ff787a5a2c08@redhat.com> (raw)
In-Reply-To: <20200225170619.GC32720@dhcp22.suse.cz>
On 25.02.20 18:06, Michal Hocko wrote:
> On Tue 25-02-20 16:09:29, David Hildenbrand wrote:
>> On 25.02.20 15:58, Michal Hocko wrote:
>>> On Thu 12-12-19 18:11:36, David Hildenbrand wrote:
>>>> We already have a way to trigger reclaiming of all reclaimable slab objects
>>>> from user space (echo 2 > /proc/sys/vm/drop_caches). Let's allow drivers
>>>> to also trigger this when they really want to make progress and know what
>>>> they are doing.
>>>
>>> I cannot say I would be fan of this. This is a global action with user
>>> visible performance impact. I am worried that we will find out that all
>>> sorts of drivers have a very good idea that dropping slab caches is
>>> going to help their problem whatever it is. We have seen the same patter
>>> in the userspace already and that is the reason we are logging the usage
>>> to the log and count invocations in the counter.
>>
>> Yeah, I decided to hold back patch 11-13 for the v1 (which I am planning
>> to post in March after more testing). What we really want is to make
>> memory offlining an alloc_contig_range() work better with reclaimable
>> objects.
>>
>>>
>>>> virtio-mem wants to use these functions when it failed to unplug memory
>>>> for quite some time (e.g., after 30 minutes). It will then try to
>>>> free up reclaimable objects by dropping the slab caches every now and
>>>> then (e.g., every 30 minutes) as long as necessary. There will be a way to
>>>> disable this feature and info messages will be logged.
>>>>
>>>> In the future, we want to have a drop_slab_range() functionality
>>>> instead. Memory offlining code has similar demands and also other
>>>> alloc_contig_range() users (e.g., gigantic pages) could make good use of
>>>> this feature. Adding it, however, requires more work/thought.
>>>
>>> We already do have a memory_notify(MEM_GOING_OFFLINE) for that purpose
>>> and slab allocator implements a callback (slab_mem_going_offline_callback).
>>> The callback is quite dumb and it doesn't really try to free objects
>>> from the given memory range or even try to drop active objects which
>>> might turn out to be hard but this sounds like a more robust way to
>>> achieve what you want.
>>
>> Two things:
>>
>> 1. memory_notify(MEM_GOING_OFFLINE) is called after trying to isolate
>> the page range and checking if we only have movable pages. Won't help
>> much I guess.
>
> You are right, I have missed that. Can we reorder those two calls?
AFAIK no (would have to look up the details, but there was a good reason
for the order, e.g., avoid races with other users of page isolation like
alloc_contig_range()).
Especially, "[PATCH RFC v4 06/13] mm: Allow to offline unmovable
PageOffline() pages via MEM_GOING_OFFLINE" (which is still impatiently
waiting for an ACK ;) ) also works around that ordering issue in a way
we discussed back then.
--
Thanks,
David / dhildenb
WARNING: multiple messages have this Message-ID (diff)
From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
virtio-dev@lists.oasis-open.org,
virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
"Michael S . Tsirkin" <mst@redhat.com>
Subject: [virtio-dev] Re: [PATCH RFC v4 12/13] mm/vmscan: Export drop_slab() and drop_slab_node()
Date: Tue, 25 Feb 2020 18:23:23 +0100 [thread overview]
Message-ID: <9c21be0c-5eef-58c2-bfb9-ff787a5a2c08@redhat.com> (raw)
In-Reply-To: <20200225170619.GC32720@dhcp22.suse.cz>
On 25.02.20 18:06, Michal Hocko wrote:
> On Tue 25-02-20 16:09:29, David Hildenbrand wrote:
>> On 25.02.20 15:58, Michal Hocko wrote:
>>> On Thu 12-12-19 18:11:36, David Hildenbrand wrote:
>>>> We already have a way to trigger reclaiming of all reclaimable slab objects
>>>> from user space (echo 2 > /proc/sys/vm/drop_caches). Let's allow drivers
>>>> to also trigger this when they really want to make progress and know what
>>>> they are doing.
>>>
>>> I cannot say I would be fan of this. This is a global action with user
>>> visible performance impact. I am worried that we will find out that all
>>> sorts of drivers have a very good idea that dropping slab caches is
>>> going to help their problem whatever it is. We have seen the same patter
>>> in the userspace already and that is the reason we are logging the usage
>>> to the log and count invocations in the counter.
>>
>> Yeah, I decided to hold back patch 11-13 for the v1 (which I am planning
>> to post in March after more testing). What we really want is to make
>> memory offlining an alloc_contig_range() work better with reclaimable
>> objects.
>>
>>>
>>>> virtio-mem wants to use these functions when it failed to unplug memory
>>>> for quite some time (e.g., after 30 minutes). It will then try to
>>>> free up reclaimable objects by dropping the slab caches every now and
>>>> then (e.g., every 30 minutes) as long as necessary. There will be a way to
>>>> disable this feature and info messages will be logged.
>>>>
>>>> In the future, we want to have a drop_slab_range() functionality
>>>> instead. Memory offlining code has similar demands and also other
>>>> alloc_contig_range() users (e.g., gigantic pages) could make good use of
>>>> this feature. Adding it, however, requires more work/thought.
>>>
>>> We already do have a memory_notify(MEM_GOING_OFFLINE) for that purpose
>>> and slab allocator implements a callback (slab_mem_going_offline_callback).
>>> The callback is quite dumb and it doesn't really try to free objects
>>> from the given memory range or even try to drop active objects which
>>> might turn out to be hard but this sounds like a more robust way to
>>> achieve what you want.
>>
>> Two things:
>>
>> 1. memory_notify(MEM_GOING_OFFLINE) is called after trying to isolate
>> the page range and checking if we only have movable pages. Won't help
>> much I guess.
>
> You are right, I have missed that. Can we reorder those two calls?
AFAIK no (would have to look up the details, but there was a good reason
for the order, e.g., avoid races with other users of page isolation like
alloc_contig_range()).
Especially, "[PATCH RFC v4 06/13] mm: Allow to offline unmovable
PageOffline() pages via MEM_GOING_OFFLINE" (which is still impatiently
waiting for an ACK ;) ) also works around that ordering issue in a way
we discussed back then.
--
Thanks,
David / dhildenb
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next prev parent reply other threads:[~2020-02-25 17:23 UTC|newest]
Thread overview: 116+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-12 17:11 [PATCH RFC v4 00/13] virtio-mem: paravirtualized memory David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2019-12-12 17:11 ` [PATCH RFC v4 01/13] ACPI: NUMA: export pxm_to_node David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2019-12-12 21:43 ` Rafael J. Wysocki
2019-12-13 9:41 ` David Hildenbrand
2019-12-13 9:41 ` David Hildenbrand
2019-12-13 9:41 ` [virtio-dev] " David Hildenbrand
2019-12-13 9:47 ` Rafael J. Wysocki
2019-12-13 9:47 ` Rafael J. Wysocki
2019-12-13 9:47 ` Rafael J. Wysocki
2019-12-12 17:11 ` David Hildenbrand
2019-12-12 17:11 ` [PATCH RFC v4 02/13] virtio-mem: Paravirtualized memory hotplug David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2019-12-12 17:11 ` David Hildenbrand
2019-12-12 17:11 ` [PATCH RFC v4 03/13] virtio-mem: Paravirtualized memory hotunplug part 1 David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2019-12-12 17:11 ` David Hildenbrand
2019-12-12 17:11 ` [PATCH RFC v4 04/13] mm: Export alloc_contig_range() / free_contig_range() David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2019-12-12 17:11 ` David Hildenbrand
2019-12-12 17:11 ` [PATCH RFC v4 05/13] virtio-mem: Paravirtualized memory hotunplug part 2 David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2019-12-12 17:11 ` David Hildenbrand
2019-12-12 17:11 ` [PATCH RFC v4 06/13] mm: Allow to offline unmovable PageOffline() pages via MEM_GOING_OFFLINE David Hildenbrand
2019-12-12 17:11 ` David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2020-02-25 18:26 ` Alexander Duyck
2020-02-25 18:26 ` [virtio-dev] " Alexander Duyck
2020-02-25 18:26 ` Alexander Duyck
2020-02-25 18:49 ` David Hildenbrand
2020-02-25 18:49 ` [virtio-dev] " David Hildenbrand
2020-02-25 18:49 ` David Hildenbrand
2020-02-25 21:46 ` Alexander Duyck
2020-02-25 21:46 ` [virtio-dev] " Alexander Duyck
2020-02-25 21:46 ` Alexander Duyck
2020-02-25 22:19 ` David Hildenbrand
2020-02-25 22:19 ` [virtio-dev] " David Hildenbrand
2020-02-25 22:19 ` David Hildenbrand
2020-02-26 16:27 ` Alexander Duyck
2020-02-26 16:27 ` [virtio-dev] " Alexander Duyck
2020-02-26 16:27 ` Alexander Duyck
2019-12-12 17:11 ` [PATCH RFC v4 07/13] virtio-mem: Allow to offline partially unplugged memory blocks David Hildenbrand
2019-12-12 17:11 ` David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2019-12-12 17:11 ` [PATCH RFC v4 08/13] mm/memory_hotplug: Introduce offline_and_remove_memory() David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2020-02-25 14:11 ` Michal Hocko
2020-02-25 14:27 ` David Hildenbrand
2020-02-25 14:27 ` [virtio-dev] " David Hildenbrand
2020-03-02 12:48 ` Michal Hocko
2020-03-02 12:53 ` David Hildenbrand
2020-03-02 12:53 ` [virtio-dev] " David Hildenbrand
2019-12-12 17:11 ` David Hildenbrand
2019-12-12 17:11 ` [PATCH RFC v4 09/13] virtio-mem: Offline and remove completely unplugged memory blocks David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2019-12-12 17:11 ` David Hildenbrand
2019-12-12 17:11 ` [PATCH RFC v4 10/13] virtio-mem: Better retry handling David Hildenbrand
2019-12-12 17:11 ` David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2019-12-12 17:11 ` [PATCH RFC v4 11/13] mm/vmscan: Move count_vm_event(DROP_SLAB) into drop_slab() David Hildenbrand
2019-12-12 17:11 ` David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2020-02-25 14:13 ` Michal Hocko
2019-12-12 17:11 ` [PATCH RFC v4 12/13] mm/vmscan: Export drop_slab() and drop_slab_node() David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2020-02-25 14:58 ` Michal Hocko
2020-02-25 15:09 ` David Hildenbrand
2020-02-25 15:09 ` [virtio-dev] " David Hildenbrand
2020-02-25 17:06 ` Michal Hocko
2020-02-25 17:23 ` David Hildenbrand [this message]
2020-02-25 17:23 ` [virtio-dev] " David Hildenbrand
2019-12-12 17:11 ` David Hildenbrand
2019-12-12 17:11 ` [PATCH RFC v4 13/13] virtio-mem: Drop slab objects when unplug continues to fail David Hildenbrand
2019-12-12 17:11 ` [virtio-dev] " David Hildenbrand
2019-12-12 17:11 ` David Hildenbrand
2019-12-13 20:15 ` [PATCH RFC v4 00/13] virtio-mem: paravirtualized memory Konrad Rzeszutek Wilk
2019-12-13 20:15 ` Konrad Rzeszutek Wilk
2019-12-16 11:03 ` David Hildenbrand
2019-12-16 11:03 ` David Hildenbrand
2019-12-16 11:03 ` [virtio-dev] " David Hildenbrand
2019-12-24 6:58 ` teawater
2019-12-24 9:28 ` David Hildenbrand
2019-12-24 9:28 ` [virtio-dev] " David Hildenbrand
2019-12-24 9:28 ` David Hildenbrand
2020-01-09 13:48 ` David Hildenbrand
2020-01-09 13:48 ` [virtio-dev] " David Hildenbrand
2020-01-29 9:41 ` David Hildenbrand
2020-01-29 9:41 ` [virtio-dev] " David Hildenbrand
2020-01-29 9:41 ` David Hildenbrand
2020-02-25 9:58 ` David Hildenbrand
2020-02-25 9:58 ` [virtio-dev] " David Hildenbrand
2020-02-25 9:58 ` David Hildenbrand
2020-06-05 8:55 ` Alex Shi
2020-06-05 8:55 ` Alex Shi
2020-06-05 9:08 ` David Hildenbrand
2020-06-05 9:08 ` [virtio-dev] " David Hildenbrand
2020-06-05 9:08 ` David Hildenbrand
2020-06-05 9:36 ` David Hildenbrand
2020-06-05 9:36 ` [virtio-dev] " David Hildenbrand
2020-06-05 9:36 ` David Hildenbrand
2020-06-05 10:05 ` David Hildenbrand
2020-06-05 10:05 ` [virtio-dev] " David Hildenbrand
2020-06-05 10:05 ` David Hildenbrand
2020-06-05 10:46 ` Alex Shi
2020-06-05 10:46 ` Alex Shi
2020-06-05 12:18 ` David Hildenbrand
2020-06-05 12:18 ` [virtio-dev] " David Hildenbrand
2020-06-05 12:18 ` David Hildenbrand
2020-06-09 3:05 ` Alex Shi
2020-06-09 3:05 ` Alex Shi
2020-06-05 10:08 ` Alex Shi
2020-06-05 10:08 ` Alex Shi
2020-06-05 10:06 ` Alex Shi
2020-06-05 10:06 ` Alex Shi
2020-01-09 13:48 ` David Hildenbrand
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