Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <a6e84fce-31e8-bdd2-8ed9-de099f5e2230@oracle.com>
Date:   Fri, 9 Jun 2023 17:28:37 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.12.0
Subject: Re: [PATCH v4] mm, compaction: Skip all non-migratable pages during
 scan
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     David Hildenbrand <david@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        John Hubbard <jhubbard@nvidia.com>,
        Steven Sistare <steven.sistare@oracle.com>,
        ying.huang@intel.com, mgorman@techsingularity.net,
        baolin.wang@linux.alibaba.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Khalid Aziz <khalid@kernel.org>
References: <ZG/I7tYY4uV/32hP@casper.infradead.org>
 <ZG/To8Z3StoVoenU@casper.infradead.org>
 <60367660-f4a3-06dc-4d17-4dbdc733ef74@oracle.com>
 <ZHDh4Jeb/vKY+nGU@casper.infradead.org>
 <f5a37f8d-d888-9085-2f2b-1e350a267396@redhat.com>
 <ZHD+eOMpZpWXNAig@casper.infradead.org>
 <e31cd404-56ce-4cad-fcc3-3a6695f750fa@redhat.com>
 <846b770c-9f63-90a2-0435-ec82484e3f74@nvidia.com>
 <ZHF2byaRlaX3W6Md@casper.infradead.org>
 <9821bd9c-7c30-8f0c-68e4-6b1d312bc032@nvidia.com>
 <ZHPydXSAfRq8sh0u@casper.infradead.org>
 <4d035744-271d-1ca3-a440-f8b1573eec96@redhat.com>
 <3c2ac70b-31a2-4e85-0ade-cb9f701525b3@oracle.com>
 <20230609151111.bb7908254853a0879db07746@linux-foundation.org>
Content-Language: en-US
From:   Khalid Aziz <khalid.aziz@oracle.com>
In-Reply-To: <20230609151111.bb7908254853a0879db07746@linux-foundation.org>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?ZlZjM1FVNlhaTndsOFNCS1JkVWcrYzk0anlERWtWa0FBakVDOWEzZ1BNZlR0?=
 =?utf-8?B?Um15eFBwWlVXZTNBMUZLWWlUd20rLzNDVWYySVZ2NjNPRTVYRTV5MHBTL3NQ?=
 =?utf-8?B?NEI0QkVKTjFYZVpyakViSk1tOFQwZjhHK2F5dTdvRHpUdTVrZE5UZ1Vtdnhy?=
 =?utf-8?B?ZlRzaHBpU0FOTENKM0ZqTStSK0ZzWjhMMGYwcy9qVEswd2czS0xzekF5REpu?=
 =?utf-8?B?djJ0eTNTOUJVWkcwWmFuMjVmU085UG5LUlpQeGx4Kzc4cXZBb2F2dS9scExW?=
 =?utf-8?B?bkh2UkJVQUNscEpJQXlOYkJ5cDBUZlcwOFcreXJxWmxMaWxrT1RJaGk1SzQ4?=
 =?utf-8?B?N1dERHduL2ZtQTlMNC9OcW56dGtEalNEc0FJMTU4ZDMrczk4eVpkaFVmL3M2?=
 =?utf-8?B?MG5hRm5jb3h2em1SaEluTXZFeHpzNlFQWGdxQVJtZTJsT2JmY0VHdzBndVd2?=
 =?utf-8?B?RkNhd1ZvdUkxR25PYWUwOHNuMm1iUVdmMFpuNlhuQ3AzeThKelFCaVBFWW4y?=
 =?utf-8?B?MExZdmFPek5OdkNPOEMxK2psNWM0ZmpQMnNxa1hJZ3p1VURudGNBdzVlNEVJ?=
 =?utf-8?B?UWdjOFA4WjJ5bFRjQVlFVlF0QnczS09uWnpZTHNRb1ZUVnhWeUdhRlAvRnVK?=
 =?utf-8?B?OWFpNHJ1V0x5Ym9ldW5hKzJhM0VaZTlGalBUUXIyVDBSVDlsSEdjOEhNVjc0?=
 =?utf-8?B?WW0rbHZDNFRjS0JiNkR5VGs4RkdTcUo4NnVhWGRiMTRSUm1pQTFxejR1aHN4?=
 =?utf-8?B?NWdlV3R4SUNETEM2QTRqMThPQXN4UG13bVFOa3RpN0V5bklyc1V4dUUzU3ov?=
 =?utf-8?B?MWFxUWpoemNTRHhDc0xobzBFWWQ0dXpKNTQxMldXRXhPUEVIeVFxWDk1eG5C?=
 =?utf-8?B?S050czZRaDluRkFFdHIwWDlhc3daTUk4SzVPZUFsVGphVGF0K0FQNkxVd015?=
 =?utf-8?B?dnRpUWtoUTM5K3p6aXpCUlNWMnVqRXVZdFB2MHRhVVM5OTVNdmNpN0FKMHZR?=
 =?utf-8?B?VDE1MWR1eXVFaDVpNEhwejZadUI1U2t4UUZ6dSt6QTl4ekxHQ1RyS3c1UjJr?=
 =?utf-8?B?cnlwd1lja0VxODBEQkNRSkZ2eGd3aVBlbmFZd05mVFl3bzNLaHhPaWkvL0hY?=
 =?utf-8?B?U1JaYkEyQUpnRHlsTGU5RWtKNFg4NHBQU0pLTkRMdlV4M2pWNVBxNTdUQzNi?=
 =?utf-8?B?WHdDV0FXOW5kNzJqdWJVNDJ0WmRqN2lEeFdGSzI0TUVlbXVIaHJubGxWUnNG?=
 =?utf-8?B?aVpnL01qZUNxVkNYbnQ1bURoeU41dGc1OHZqRUkzcXpOWk9oQkVrbmJ5dUVi?=
 =?utf-8?B?dDl0bkFTMTZPQ00zKys5cFYwczYvZURtbG11WXgxNitieWJvdjRVVFh0Qmpp?=
 =?utf-8?B?NUlucFJrYkpDMEFheU9NSHRvVGVYSnlTeHFJaFR2byt5Y1lETjRKM1NqTXdN?=
 =?utf-8?B?eXpVZzBpd1Rrd0VmSFNSbVNwejBKckZNNXNoaC84TjM2b01UOU5FaDA3UXZ6?=
 =?utf-8?B?dURtT3JxSFUrbGJIOVhRdENGSnlHMEptNURrS1lWOUlzS3V4aDFUOEIralhq?=
 =?utf-8?B?L09vK0R3SnBRQmZGbEluN3MvTXlWeE0xcDQ3UVhJVEdaVUd4ZmFqSys4T3Y2?=
 =?utf-8?B?MVluRVNGSUJyVjNYWEJCbVF5WVZNWnV5TjdKZzBxeVlOVWE5ckpaMTBGeWp4?=
 =?utf-8?B?VnRyaGpZTzNiQXpMRHo0YnVQM0ZVdVhNdU1lalNOMWl0SnBCWGNoODZkQUc4?=
 =?utf-8?B?L2JZZVN1Wm80YkxTUjhCZHJVakZSNEhPd2l5M0Yvank4TlJmWDRyRmJmQkMx?=
 =?utf-8?B?SWc0ZDdPRWpoOEpFM2pKaG50VldlMEhVbU5xajEyck1tWkxoSDhUaHdWdHJX?=
 =?utf-8?B?WnNPeEpPdTNPYXUzVUlSZ3B3VjgwdjJNSnNFZjh3U3RWaHNkWGw4QXlLZm1K?=
 =?utf-8?B?RW1LZ3RyMmhqRXRDRGVuOFFYQzdXMStSblFTbnc2SDNkTlZteDc5R3kwQmFO?=
 =?utf-8?B?TGFJUDRiT29ac2JzbXJFam9ud2FjRUhkL090NzZMTDd0WDNMOVZldjdCYk5J?=
 =?utf-8?B?V204SXhuaGQxRnRHRnR2dm14Tkppei91NFk0amhOZ2VsZWJGNmNWUzA4dllm?=
 =?utf-8?Q?2ZhsxgtMCJGqixlCpIZi1JXNr?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: =?utf-8?B?YzJPZGN0WU45cDR5aFpYSnR1bzlvS1B3emIva0cxdnpXMFRpT3RxMHVJYjlI?=
 =?utf-8?B?cU1FTlF4WlBsakFyeHFJOExUemZqRDllUUlDWExaVVBIbzF1VmVxMkNUQXkx?=
 =?utf-8?B?OXJjQ2lxUGZaTEJGQzcvWS9BZjY5cE9FTGQ2Y1hNYUUvbitBNlpoTmRFZFNM?=
 =?utf-8?B?eW1uVC95TEZjWm1tZjZEUWlTNURUa3F6U05oQit4TnAyRW9Td2xWalllTGQy?=
 =?utf-8?B?OEZMVkl3UEE5bmRpRVMxSVMweXN6bDQ2dzdPd05sTWxUa3RWZzJrejdXeUVD?=
 =?utf-8?B?dUs1d0g0TEJhR3cvM2QwSFphRm9Hbm9QNU5xeTdHanBpa2JucktkREhDNngy?=
 =?utf-8?B?NEFDRStsNlBLdWVERTJYem0rWGtlR3lFUTJUbVBQSnVycEZpVzcvQ2VpYld5?=
 =?utf-8?B?MTlYdkJJNnNML3gvb3RwcWZiY2tXZ0w5WVBWei9FMnFIWk9COERWajVOWEdw?=
 =?utf-8?B?RWdoSWw3N3krc0RDT1pSMkJrOU5xWXNMd3dBeDBGdW0welh3S2FyanpNc0s2?=
 =?utf-8?B?bzNlLzIrc2NVc0xCUTV1c1pKVnh0MnZyOTI4VnB6SSs5am9ndU4yNndyQ2dG?=
 =?utf-8?B?STh4aERMOU56SFE0OUxiNE9TMm5XZ3pyVG1QMWY0K1BpdEx4aFZUWm1JelI1?=
 =?utf-8?B?dlJnY2cyYURydmJIekdNaWlaMmxnUWNqbk5oMGRHZVc0LzlNMm12cnJkenZG?=
 =?utf-8?B?Yy9lZ1E3cWhEUWd5NFo0YlFYRUdOQmZXNHN0cVlDeUNieEs4blNvcnNGYnI5?=
 =?utf-8?B?Z3VoQnJROHYwMkd1UE13QTZ5a1hlOTJPOUN1aHZJc2prYXFaL1RSMTBDcDV4?=
 =?utf-8?B?dDFiMUJ1Q0hTek1oNzhnSGh4UkUyS092Z2VveFE4U1J6eVk3Qy9sUjFVZGRM?=
 =?utf-8?B?Zzdxb1hhWDVhMklPNUR6R01vaU9kTjRuZmtPUjF2cjhycWlWZE1xL1NsRk1a?=
 =?utf-8?B?SzY4MWYrdXlRUjVVN2lOV0d6U3VEdHc5SnNOeSt0VzRjSHgzRlBMSGJDeE1j?=
 =?utf-8?B?OHRmU3RtWmlHZENaaCt3SmV6Um96ekNwQVZxd25tL3diN0JlYktKMkZvMUt3?=
 =?utf-8?B?amhnTzZldm5nRG5tMlA4UnNMTGhsTUVhTzNwbm95UDlZOVBVeS8xc0JaM2lY?=
 =?utf-8?B?WlZkUWZYb0xSczFNWW1KYk1xaTh6RGxOU3RWb2tCRzNVeFpheGZjNG1nLy94?=
 =?utf-8?B?elB3aTNNcHFEN0tib0dtajFLYkNhL3FZZFhnT3RwdGJkazcrN2tYTnNGZFpz?=
 =?utf-8?B?R0dTRWptaGxFNkcvTlJrQlFNYWgzMG5SMzVNRHIvdWVEcmNySVZId0paMjRn?=
 =?utf-8?B?NGNLVWIzdFFBN2p4eDNCVlMyTENEUkMwOXhOaVozU3FLYkwwenV4Ulc1QUhn?=
 =?utf-8?B?V0F2ZytnQURpUEQwbUpPTkxBSUdBcWRkZ2FLQW9JekpNdi8xWVdLem9GSHBm?=
 =?utf-8?B?aDZFZjRDZHRVWS9ST09ZVk05UncwY2hzWEdpa0dnPT0=?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 26d7e271-429b-4b51-6c0c-08db694141ee
X-MS-Exchange-CrossTenant-AuthSource: CH3PR10MB6810.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Jun 2023 23:28:40.7413
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: rmxFOGUxwodPGl6blkJzrn+/FBpgXz/UHOAxlW/3SMNvlTA2vX9JtzK+dbaHuQosq3PEyZ7NyMYeEUcKlHfNjQ==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR10MB6694
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.254,Aquarius:18.0.957,Hydra:6.0.573,FMLib:17.11.176.26
 definitions=2023-06-09_17,2023-06-09_01,2023-05-22_02
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 suspectscore=0 bulkscore=0
 spamscore=0 mlxlogscore=999 adultscore=0 phishscore=0 malwarescore=0
 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2305260000
 definitions=main-2306090199
X-Proofpoint-ORIG-GUID: Q5-su78ceuSoFxHNXt5LQlRJ1MJ16JVh
X-Proofpoint-GUID: Q5-su78ceuSoFxHNXt5LQlRJ1MJ16JVh
X-Spam-Status: No, score=-2.9 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_DNSWL_LOW,
        RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE,
        T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 6/9/23 16:11, Andrew Morton wrote:
> On Tue, 30 May 2023 09:42:33 -0600 Khalid Aziz <khalid.aziz@oracle.com> wrote:
> 
>>> I completely agree that we should be careful with such mapcount vs. pagecount checks, and if we can use something
>>> better, let's use something *better*.
>>
>> When we have a reliable folio_maybe_dma_longterm_pinned() function, it will be better to call that instead of doing
>> refcount vs mapcount check. Until that better function to check for pinned pages is in place, may I propose that the
>> current patch fixes a customer problem though not optimally and is a good enough working solution. When a better
>> function is in place, page_has_extra_refs() function can be updated to rely on this other function instead of refcount
>> vs mapcount.
> 
> We seem rather stuck with this patch.  I think I'll drop it while we
> ponder a way forward.

Hi Andrew,

I would still recommend that we use this patch and fix the existing problem, unless there are objections from other 
people. This is not an optimal solution but it works and is similar to what kernel does elsewhere. When a better 
function to check pinned pages is available, we start using that function instead.

Thanks,
Khalid