From: Mike Kravetz <mike.kravetz@oracle.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
David Hildenbrand <david@redhat.com>,
Michal Hocko <mhocko@suse.com>,
Oscar Salvador <osalvador@suse.de>, Zi Yan <ziy@nvidia.com>,
Muchun Song <songmuchun@bytedance.com>,
Naoya Horiguchi <naoya.horiguchi@linux.dev>,
David Rientjes <rientjes@google.com>
Subject: Re: [PATCH 5/8] hugetlb: document the demote sysfs interfaces
Date: Mon, 16 Aug 2021 18:04:52 -0700 [thread overview]
Message-ID: <a87f3a90-9949-153f-fb97-c5381443a963@oracle.com> (raw)
In-Reply-To: <20210816162829.a228c4629b411900702b7f5f@linux-foundation.org>
On 8/16/21 4:28 PM, Andrew Morton wrote:
> On Mon, 16 Aug 2021 15:49:50 -0700 Mike Kravetz <mike.kravetz@oracle.com> wrote:
>
>> Describe demote and demote_size interfaces.
>>
>> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
>> ---
>> Documentation/admin-guide/mm/hugetlbpage.rst | 29 ++++++++++++++++++--
>> 1 file changed, 27 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst
>> index 8abaeb144e44..902059a0257b 100644
>> --- a/Documentation/admin-guide/mm/hugetlbpage.rst
>> +++ b/Documentation/admin-guide/mm/hugetlbpage.rst
>> @@ -234,8 +234,12 @@ will exist, of the form::
>>
>> hugepages-${size}kB
>>
>> -Inside each of these directories, the same set of files will exist::
>> +Inside each of these directories, the set of files contained in ``/proc``
>> +will exist. In addition, two additional interfaces for demoting huge
>> +pages will exist::
>>
>> + demote
>> + demote_size
>> nr_hugepages
>> nr_hugepages_mempolicy
>> nr_overcommit_hugepages
>> @@ -243,7 +247,28 @@ Inside each of these directories, the same set of files will exist::
>> resv_hugepages
>> surplus_hugepages
>>
>> -which function as described above for the default huge page-sized case.
>> +The demote interfaces provide the ability to split a huge page into
>> +smaller huge pages. For example, the x86 architecture supports both
>> +1GB and 2MB huge pages sizes. A 1GB huge page can be split into 512
>> +2MB huge pages. The demote interfaces are:
>> +
>> +demote_size
>> + is the size of demoted pages. When a page is demoted a corresponding
>> + number of huge pages of demote_size will be created. For huge pages
>> + of the smallest supported size (2MB on x86), demote_size will be the
>> + system page size (PAGE_SIZE). If demote_size is the system page size
>> + then demoting a page will simply free the huge page. demote_size is
>> + a read only interface.
>> +
>> +demote
>> + is used to demote a number of huge pages. A user with root privileges
>> + can write to this file. It may not be possible to demote the
>> + requested number of huge pages. To determine how many pages were
>> + actually demoted, compare the value of nr_hugepages before and after
>> + writing to the demote interface. demote is a write only interface.
>> +
>> +The interfaces which are the same as in ``/proc`` function as described
>> +above for the default huge page-sized case.
>
> Are these new demote interfaces duplicated in /proc?
> Documentation/admin-guide/mm/hugetlbpage.rst says "The ``/proc``
> interfaces discussed above have been retained for backwards
> compatibility.", so new interfaces need not appear in /proc?
>
The new demote interfaces are only in sysfs, they are not /proc.
--
Mike Kravetz
next prev parent reply other threads:[~2021-08-17 1:05 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-16 22:49 [PATCH RESEND 0/8] hugetlb: add demote/split page functionality Mike Kravetz
2021-08-16 22:49 ` [PATCH 1/8] hugetlb: add demote hugetlb page sysfs interfaces Mike Kravetz
2021-08-16 22:49 ` [PATCH 2/8] hugetlb: add HPageCma flag and code to free non-gigantic pages in CMA Mike Kravetz
2021-08-16 22:49 ` [PATCH 3/8] hugetlb: add demote bool to gigantic page routines Mike Kravetz
2021-08-16 22:49 ` [PATCH 4/8] hugetlb: add hugetlb demote page support Mike Kravetz
2021-08-16 22:49 ` [PATCH 5/8] hugetlb: document the demote sysfs interfaces Mike Kravetz
2021-08-16 23:28 ` Andrew Morton
2021-08-17 1:04 ` Mike Kravetz [this message]
2021-09-21 13:52 ` Aneesh Kumar K.V
2021-09-21 17:17 ` Mike Kravetz
2021-08-16 22:49 ` [PATCH 6/8] hugetlb: vmemmap optimizations when demoting hugetlb pages Mike Kravetz
2021-08-16 22:49 ` [PATCH 7/8] hugetlb: prepare destroy and prep routines for vmemmap optimized pages Mike Kravetz
2021-08-16 22:49 ` [PATCH 8/8] hugetlb: Optimized demote vmemmap optimizatized pages Mike Kravetz
2021-08-16 23:23 ` [PATCH RESEND 0/8] hugetlb: add demote/split page functionality Andrew Morton
2021-08-17 0:17 ` Mike Kravetz
2021-08-17 0:39 ` Andrew Morton
2021-08-17 0:58 ` Mike Kravetz
2021-08-16 23:27 ` Andrew Morton
2021-08-17 0:46 ` Mike Kravetz
2021-08-17 1:46 ` Andrew Morton
2021-08-17 7:30 ` David Hildenbrand
2021-08-17 16:19 ` Mike Kravetz
2021-08-17 18:49 ` David Hildenbrand
2021-08-24 22:08 ` Mike Kravetz
2021-08-27 17:22 ` Vlastimil Babka
2021-08-27 23:04 ` Mike Kravetz
2021-08-30 10:11 ` Vlastimil Babka
2021-09-02 18:17 ` Mike Kravetz
2021-09-06 14:40 ` Vlastimil Babka
[not found] ` <20210907085001.3773-1-hdanton@sina.com>
2021-09-08 21:00 ` Mike Kravetz
2021-09-09 11:54 ` Michal Hocko
2021-09-09 13:45 ` Vlastimil Babka
2021-09-09 21:31 ` Mike Kravetz
2021-09-10 8:20 ` Michal Hocko
2021-09-11 0:11 ` Mike Kravetz
2021-09-13 15:50 ` Michal Hocko
2021-09-15 16:57 ` Mike Kravetz
2021-09-17 20:44 ` Mike Kravetz
-- strict thread matches above, loose matches on Subject: below --
2021-07-21 23:05 [PATCH " Mike Kravetz
2021-07-21 23:05 ` [PATCH 5/8] hugetlb: document the demote sysfs interfaces Mike Kravetz
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