From: Gavin Shan <gshan@redhat.com>
To: Alexander Duyck <alexander.duyck@gmail.com>
Cc: linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
David Hildenbrand <david@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
shan.gavin@gmail.com
Subject: Re: [PATCH v4 3/4] mm/page_reporting: Allow driver to specify reporting order
Date: Fri, 25 Jun 2021 14:24:06 +1000 [thread overview]
Message-ID: <fef3e1a0-4a3a-70a2-233d-cd4bda3c8fab@redhat.com> (raw)
In-Reply-To: <ad137ea5-9fb7-d543-f841-e54dafd805b5@redhat.com>
On 6/25/21 2:00 PM, Gavin Shan wrote:
> On 6/25/21 11:19 AM, Alexander Duyck wrote:
>> On Thu, Jun 24, 2021 at 4:46 PM Gavin Shan <gshan@redhat.com> wrote:
>>>
>>> The page reporting order (threshold) is sticky to @pageblock_order
>>> by default. The page reporting can never be triggered because the
>>> freeing page can't come up with a free area like that huge. The
>>> situation becomes worse when the system memory becomes heavily
>>> fragmented.
>>>
>>> For example, the following configurations are used on ARM64 when 64KB
>>> base page size is enabled. In this specific case, the page reporting
>>> won't be triggered until the freeing page comes up with a 512MB free
>>> area. That's hard to be met, especially when the system memory becomes
>>> heavily fragmented.
>>>
>>> PAGE_SIZE: 64KB
>>> HPAGE_SIZE: 512MB
>>> pageblock_order: 13 (512MB)
>>> MAX_ORDER: 14
>>>
>>> This allows the drivers to specify the page reporting order when the
>>> page reporting device is registered. It falls back to @pageblock_order
>>> if it's not specified by the driver. The existing users (hv_balloon
>>> and virtio_balloon) don't specify it and @pageblock_order is still
>>> taken as their page reporting order. So this shouldn't introduce any
>>> functional changes.
>>>
>>> Signed-off-by: Gavin Shan <gshan@redhat.com>
>>> Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
>>> ---
>>> include/linux/page_reporting.h | 3 +++
>>> mm/page_reporting.c | 6 ++++++
>>> 2 files changed, 9 insertions(+)
>>>
>>> diff --git a/include/linux/page_reporting.h b/include/linux/page_reporting.h
>>> index 3b99e0ec24f2..fe648dfa3a7c 100644
>>> --- a/include/linux/page_reporting.h
>>> +++ b/include/linux/page_reporting.h
>>> @@ -18,6 +18,9 @@ struct page_reporting_dev_info {
>>>
>>> /* Current state of page reporting */
>>> atomic_t state;
>>> +
>>> + /* Minimal order of page reporting */
>>> + unsigned int order;
>>> };
>>>
>>> /* Tear-down and bring-up for page reporting devices */
>>> diff --git a/mm/page_reporting.c b/mm/page_reporting.c
>>> index 34bf4d26c2c4..382958eef8a9 100644
>>> --- a/mm/page_reporting.c
>>> +++ b/mm/page_reporting.c
>>> @@ -329,6 +329,12 @@ int page_reporting_register(struct page_reporting_dev_info *prdev)
>>> goto err_out;
>>> }
>>>
>>> + /*
>>> + * Update the page reporting order if it's specified by driver.
>>> + * Otherwise, it falls back to @pageblock_order.
>>> + */
>>> + page_reporting_order = prdev->order ? : pageblock_order;
>>> +
>>
>> An alternative to this would be to look at setting up some
>> comparisons. I might add another variable and do something like:
>> order = prdev->order ? : pageblock_order;
>> if (order < page_reporting_order)
>> page_reporting_order = order;
>>
>> You could essentially do something similar in the previous patch but
>> just use pageblock_order directly rather than having to add a local
>> variable.
>>
>> That way if you need to still pull down the page reporting order you
>> can do so without prdev->order or pageblock_order overwriting the
>> value and pushing it back up.
>>
>
> Thanks, Alex. Lets do both in v5, which will be posted shortly.
>
Alex, I just posted v5 to have the checks you suggested. Could
you help to have a quick scan. It's pointless to let Andrew
drop the patches and apply the last one again :)
Thanks,
Gavin
next prev parent reply other threads:[~2021-06-25 2:22 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-25 1:47 [PATCH v4 0/4] mm/page_reporting: Make page reporting work on arm64 with 64KB page size Gavin Shan
2021-06-25 1:47 ` [PATCH v4 1/4] mm/page_reporting: Fix code style in __page_reporting_request() Gavin Shan
2021-06-25 1:47 ` [PATCH v4 2/4] mm/page_reporting: Export reporting order as module parameter Gavin Shan
2021-06-25 1:14 ` Alexander Duyck
2021-06-25 3:58 ` Gavin Shan
2021-06-25 5:53 ` Michael S. Tsirkin
2021-06-25 6:08 ` Gavin Shan
2021-06-25 1:47 ` [PATCH v4 3/4] mm/page_reporting: Allow driver to specify reporting order Gavin Shan
2021-06-25 1:19 ` Alexander Duyck
2021-06-25 4:00 ` Gavin Shan
2021-06-25 4:24 ` Gavin Shan [this message]
2021-06-25 5:48 ` Michael S. Tsirkin
2021-06-25 6:04 ` Gavin Shan
2021-06-25 1:47 ` [PATCH v4 4/4] virtio_balloon: Specify page reporting order if needed Gavin Shan
2021-06-25 5:57 ` Michael S. Tsirkin
2021-06-25 6:11 ` Gavin Shan
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