Received-SPF: pass (google.com: domain of linux-kernel+bounces-206739-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
From: Zi Yan <ziy@nvidia.com>
To: "Pankaj Raghav (Samsung)" <kernel@pankajraghav.com>, willy@infradead.org
Cc: david@fromorbit.com, djwong@kernel.org, chandan.babu@oracle.com,
 brauner@kernel.org, akpm@linux-foundation.org, mcgrof@kernel.org,
 linux-mm@kvack.org, hare@suse.de, linux-kernel@vger.kernel.org,
 yang@os.amperecomputing.com, linux-xfs@vger.kernel.org, p.raghav@samsung.com,
 linux-fsdevel@vger.kernel.org, hch@lst.de, gost.dev@samsung.com,
 cl@os.amperecomputing.com, john.g.garry@oracle.com
Subject: Re: [PATCH v7 05/11] mm: split a folio in minimum folio order chunks
Date: Fri, 07 Jun 2024 16:51:04 -0400
Message-ID: <45567EBA-5856-4BBC-8C02-EAE03A676B94@nvidia.com>
In-Reply-To: <20240607203026.zj3akxdjeykchnnf@quentin>
References: <20240607145902.1137853-1-kernel@pankajraghav.com>
 <20240607145902.1137853-6-kernel@pankajraghav.com>
 <75CCE180-EC90-4BDC-B5D8-0ED1B710BE49@nvidia.com>
 <20240607203026.zj3akxdjeykchnnf@quentin>
Content-Type: multipart/signed;
 boundary="=_MailMate_06406E61-B432-4EC8-A71E-9C23CFD2670B_=";
 micalg=pgp-sha512; protocol="application/pgp-signature"
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0:
	=?us-ascii?Q?83zIBuxpfKz0e15DjIZZpsQ8zmnibiGnmPbk1XtMjh9IGl8XZeFksrvBaS3o?=
 =?us-ascii?Q?hMDbttzMx23rHt2hrhrMoTbjOzc/cv10K4kWsqBgkl/IlHY4bNQMVN7fhkeD?=
 =?us-ascii?Q?haa2b0F8QIDJr7uTqkIfcMkk/T3I44I5iyif2x5LuEC/sHqmRp1b8s1+avgQ?=
 =?us-ascii?Q?LAGzAxzgFlOD08SyTvjiHxqgrijhDz8f6v5nkzbV6pAGQgvePgASFUSSykto?=
 =?us-ascii?Q?wrRs6gZ2ACpN6GXc9bjjQjKDsoRQgJ/ZD4SQjH4qhkev+g3ChdNkTpgKe5lQ?=
 =?us-ascii?Q?OWYGC81tcGEK8Nf6LJMpeIMb6Gh0OlBOzrFYaXETFkKbw0wV2DvGcPc8hvUV?=
 =?us-ascii?Q?8HQjMcN0tT5M3SLm2Gj3MB9PPT01IZ/bYLKaR78dWjxo0PwJ3MC73Qs6daI7?=
 =?us-ascii?Q?C+IHH82fxbfCIabMKrAPxE4fQZZkXl2WY3pT5TkVStGn6n2T4xtGdsRdfwGS?=
 =?us-ascii?Q?vwjmf7jgu9RNlkO/lOJJVKogDJJdfK71we32UU9ZSAJrU92oxRU5I6eucpGS?=
 =?us-ascii?Q?aPbv7wOpTx56l6Mq5ps8ZZvCnMIITRkstsra6LhGXxVSsUOZ3SdaB1BXznVs?=
 =?us-ascii?Q?qHlAmvT3n4igQscSIht4qTfrS6jhsrzcrogfaAHkJTbJ0Oaa5K1YLhXOhKHX?=
 =?us-ascii?Q?zMeJDW1HQCl/hUoovs0mfD1f8gd5kvKVomiOXE2NRKATTsBIdut7pMPVt3FC?=
 =?us-ascii?Q?4cJ9QK/dH2DwpdSwZFL+SUqCEDEYS1w1N/rW+Vj94UHQScsoa9cX6k1Bnh7G?=
 =?us-ascii?Q?KJ1do3ae1echSViMDNs2WmMa7TQiRNbcjCG+00Pv1Flql2xWd0A/dkwxMBWK?=
 =?us-ascii?Q?i4DmIoIggFpbxarjLQtOAiosLTJH+dTZtW5/dBdPe0eu0hlOSX5fj5afK7fA?=
 =?us-ascii?Q?SsN/xK2LsEcrxE48x5GW3yHsNHdJkj8sGu5NJ1TRyVhNCfXgpe2qABxiG9Xp?=
 =?us-ascii?Q?q3KPXHOs3gNLCq4X53dGBiC5NcJA4JZtCDLkKO9KyizeUfHKPKDTI9OXlvwf?=
 =?us-ascii?Q?0P2G9PxGG/9LmiwUYUDkZg3BBaLOh/Z2hXbWhHZA+MnPOkVpGTkK4kHCsA3t?=
 =?us-ascii?Q?o80kqukm6AUskMijJBU1NwgGGe8WEnB0voNXol0ByPZgyUObXvsVWGEE5TvF?=
 =?us-ascii?Q?Qs570nhEGU45l7hEi02TYBrGqRnlfv+6CgLw3K369Lk8Qg+7afN65OSDqufs?=
 =?us-ascii?Q?K1/D57uwJaf+S3QTtKTh7P9PTB/sq5Ou2T/UxxqwRbclWH/gJr7dJRELz3W6?=
 =?us-ascii?Q?STlVEmgF7g1XiZ/9XdQXkW+eUMNoJZ+uAZW72LKzbNNLoTbs6N4lfKPZ4+rl?=
 =?us-ascii?Q?iLLNVD7pVGlHEd54JHqAhsL1Jvoby68LSWY+2hfe1g2A8otGfr8HAoGHnczx?=
 =?us-ascii?Q?bPqOBeyRdGE+grYAfjK3jeRr2HsvzOkYjKxAe46Q/GbqinV3IbxuLmOA76AB?=
 =?us-ascii?Q?eAvqgXKC6L30/HpPuudpV28AlmzUSRmnqRH+1B8Wq7cw2a9qD9EutKSnypMX?=
 =?us-ascii?Q?lviOwEbKEu6NcKmuTcM4v3qv0+s3o680bGYPVqwYAMeXYHX+L6oixhzcO5Fc?=
 =?us-ascii?Q?lHxAg3MSzSSfaNK59WUtb7YUbUwkHP7JwILZBuWc?=
X-OriginatorOrg: Nvidia.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 5849a208-deb8-43fd-3d82-08dc87338e02
X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB5744.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Jun 2024 20:51:07.7055
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: 9oV2oDU+4OzASooMAX+E0AFUbreFJy3gJgt4q2i1fRsI20qRgCaug1S2FkbjFoZO
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA3PR12MB9179

--=_MailMate_06406E61-B432-4EC8-A71E-9C23CFD2670B_=
Content-Type: text/plain

On 7 Jun 2024, at 16:30, Pankaj Raghav (Samsung) wrote:

> On Fri, Jun 07, 2024 at 12:58:33PM -0400, Zi Yan wrote:
>> Hi Pankaj,
>>
>> Can you use ziy@nvidia.com instead of zi.yan@sent.com? Since I just use the latter
>> to send patches. Thanks.
>
> Got it!
>
>>
>> On 7 Jun 2024, at 10:58, Pankaj Raghav (Samsung) wrote:
>>
>>> From: Luis Chamberlain <mcgrof@kernel.org>
>>>
>>> split_folio() and split_folio_to_list() assume order 0, to support
>>> minorder for non-anonymous folios, we must expand these to check the
>>> folio mapping order and use that.
>>>
>>> Set new_order to be at least minimum folio order if it is set in
>>> split_huge_page_to_list() so that we can maintain minimum folio order
>>> requirement in the page cache.
>>>
>>> Update the debugfs write files used for testing to ensure the order
>>> is respected as well. We simply enforce the min order when a file
>>> mapping is used.
>>>
>>> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
>>> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
>>> ---
>>>  include/linux/huge_mm.h | 14 ++++++++---
>>>  mm/huge_memory.c        | 55 ++++++++++++++++++++++++++++++++++++++---
>>>  2 files changed, 61 insertions(+), 8 deletions(-)
>>>
>>
>> <snip>
>>
>>>
>>> +int split_folio_to_list(struct folio *folio, struct list_head *list)
>>> +{
>>> +	unsigned int min_order = 0;
>>> +
>>> +	if (!folio_test_anon(folio)) {
>>> +		if (!folio->mapping) {
>>> +			count_vm_event(THP_SPLIT_PAGE_FAILED);
>>
>> You should only increase this counter when the input folio is a THP, namely
>> folio_test_pmd_mappable(folio) is true. For other large folios, we will
>> need a separate counter. Something like MTHP_STAT_FILE_SPLIT_FAILED.
>> See enum mthp_stat_item in include/linux/huge_mm.h.
>>
> Hmm, but we don't have mTHP support for non-anonymous memory right? In
> that case it won't be applicable for file backed memory?

Large folio support in page cache precedes mTHP (large anonymous folio),
thanks to willy's work. mTHP is more like a subset of large folio.
There is no specific counters for page cache large folio. If you think
it is worth tracking folios with orders between 0 and 9 (exclusive),
you can add counters. Matthew, what is your take on this?


--
Best Regards,
Yan, Zi

--=_MailMate_06406E61-B432-4EC8-A71E-9C23CFD2670B_=
Content-Description: OpenPGP digital signature
Content-Disposition: attachment; filename=signature.asc
Content-Type: application/pgp-signature; name=signature.asc

-----BEGIN PGP SIGNATURE-----
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=j0MH
-----END PGP SIGNATURE-----

--=_MailMate_06406E61-B432-4EC8-A71E-9C23CFD2670B_=--