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([2a01:599:920:8ca1:a0b5:9e51:26ba:6a2b]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3675a0d9f9dsm10098082f8f.41.2024.07.01.07.03.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Jul 2024 07:03:01 -0700 (PDT) Message-ID: Date: Mon, 1 Jul 2024 16:03:00 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 2/2] mm/migrate: move NUMA hinting fault folio isolation + checks under PTL To: Zi Yan , "Huang, Ying" Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton References: <20240620212935.656243-1-david@redhat.com> <20240620212935.656243-3-david@redhat.com> <0F4ABC1D-7A26-4AE2-BCAA-3EA906FB13A7@nvidia.com> <9af34a6b-ca56-4a64-8aa6-ade65f109288@redhat.com> <87ed8do6kl.fsf@yhuang6-desk2.ccr.corp.intel.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A4023A002D X-Stat-Signature: ej64ugofnfpsynmyqch88nhxnxqiztf6 X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1719842586-196198 X-HE-Meta: U2FsdGVkX1/cnjiq3lq5kGkimKk6BQGV4JGe1aKZkUKqYdG6i08vMgOpbmvMvitBPLMUYgUHWjruafIIH0uGl3xYeixBRQeWt3xIcEMIQmTgWSXpOEN34nzTWTvpJhFIrPjYPi2lgTK/f66P8vP+2NRWZ085iuk3yVMiPHcYT7YtPHYGtmkePxtxdmawizLWS/V5aOBYYfBSpmTRb+6cxW0aCuuokPs5lRKrZ+NlSDErCweS3KLJn+j/QwNoC84rGVf3+gSulTGv77zojrr1ziGtjQaJ3GuA5ynUmuhOHJD7EpHKIm1572MVcg0UgPwuk9z26qyUUSnDvNGox/ctHCmXATNj4fOFj5uWy/EOKD2wPFSwkbfusDQk16+ovyyRnwTujvDg+v90Fc1k5l9N4RrdJJeyqlMgUNjOl73NmPtHiADbJL0irUWtA6ZUlgDMfgEmajDBmqziMUOewHm6r4VxRBBADP8ZxsL3xMbjFdfY4LjKVfHZh/EmTQa4MXOnTEU2eKPvRsl+WwFlmE+sy33ueKsuE4nV34cuqwjTtjOaW+JXGOQ5OiwTXx1/fCJbOYtpiEneL8YAryn35a2aYnB505ftEipMTQVsuEW48l6mQhkIKHuvb+57gVsaZlOGhzdr8P0MVHPunTEibKkswUg0KfUPiUDtffbKClJR/wI68LL+reEhLGDTa1YVJBdrQYMdr5zsrwGWX9DVEZsAhDFuaR7nBlsiwRQz7g7E9LIHqbEauhlfOqR8/Cz+uNtijFW1qeJ8+52Dlx/zqqiEC3ud9HGTcDDBu5wgiyIx6T88a1V9MyfUQDGQ62v776pRs5GzM60w6x46cbMxrX1f/fpe9RkgokDbSpdTAiWOqlOZ2DApc1nSxZM8MLVflMvhj+TCKOORDYe7AGoqajklIxY4pWp93fmjAUk25XRNkaWkdiN6emqHxLVYuSUUhEylWvhcmCgobWxe67NKYUt ey+Q09Vh 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 01.07.24 15:50, Zi Yan wrote: > On 1 Jul 2024, at 4:32, Huang, Ying wrote: > >> "Zi Yan" writes: >> >>> On Wed Jun 26, 2024 at 12:49 PM EDT, David Hildenbrand wrote: >>>> On 21.06.24 22:48, Zi Yan wrote: >>>>> On 21 Jun 2024, at 16:18, David Hildenbrand wrote: >>>>> >>>>>> On 21.06.24 15:44, Zi Yan wrote: >>>>>>> On 20 Jun 2024, at 17:29, David Hildenbrand wrote: >>>>>>> >>>>>>>> Currently we always take a folio reference even if migration will not >>>>>>>> even be tried or isolation failed, requiring us to grab+drop an additional >>>>>>>> reference. >>>>>>>> >>>>>>>> Further, we end up calling folio_likely_mapped_shared() while the folio >>>>>>>> might have already been unmapped, because after we dropped the PTL, that >>>>>>>> can easily happen. We want to stop touching mapcounts and friends from >>>>>>>> such context, and only call folio_likely_mapped_shared() while the folio >>>>>>>> is still mapped: mapcount information is pretty much stale and unreliable >>>>>>>> otherwise. >>>>>>>> >>>>>>>> So let's move checks into numamigrate_isolate_folio(), rename that >>>>>>>> function to migrate_misplaced_folio_prepare(), and call that function >>>>>>>> from callsites where we call migrate_misplaced_folio(), but still with >>>>>>>> the PTL held. >>>>>>>> >>>>>>>> We can now stop taking temporary folio references, and really only take >>>>>>>> a reference if folio isolation succeeded. Doing the >>>>>>>> folio_likely_mapped_shared() + golio isolation under PT lock is now similar >>>>>>>> to how we handle MADV_PAGEOUT. >>>>>>>> >>>>>>>> While at it, combine the folio_is_file_lru() checks. >>>>>>>> >>>>>>>> Signed-off-by: David Hildenbrand >>>>>>>> --- >>>>>>>> include/linux/migrate.h | 7 ++++ >>>>>>>> mm/huge_memory.c | 8 ++-- >>>>>>>> mm/memory.c | 9 +++-- >>>>>>>> mm/migrate.c | 81 +++++++++++++++++++---------------------- >>>>>>>> 4 files changed, 55 insertions(+), 50 deletions(-) >>>>>>> >>>>>>> LGTM. Reviewed-by: Zi Yan >>>>>>> >>>>>>> One nit below: >>>>>>> >>>>>>> >>>>>>> >>>>>>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>>>>>>> index fc27dabcd8e3..4b2817bb2c7d 100644 >>>>>>>> --- a/mm/huge_memory.c >>>>>>>> +++ b/mm/huge_memory.c >>>>>>>> @@ -1688,11 +1688,13 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf) >>>>>>>> if (node_is_toptier(nid)) >>>>>>>> last_cpupid = folio_last_cpupid(folio); >>>>>>>> target_nid = numa_migrate_prep(folio, vmf, haddr, nid, &flags); >>>>>>>> - if (target_nid == NUMA_NO_NODE) { >>>>>>>> - folio_put(folio); >>>>>>>> + if (target_nid == NUMA_NO_NODE) >>>>>>>> + goto out_map; >>>>>>>> + if (migrate_misplaced_folio_prepare(folio, vma, target_nid)) { >>>>>>>> + flags |= TNF_MIGRATE_FAIL; >>>>>>>> goto out_map; >>>>>>>> } >>>>>>>> - >>>>>>>> + /* The folio is isolated and isolation code holds a folio reference. */ >>>>>>>> spin_unlock(vmf->ptl); >>>>>>>> writable = false; >>>>>>>> >>>>>>>> diff --git a/mm/memory.c b/mm/memory.c >>>>>>>> index 118660de5bcc..4fd1ecfced4d 100644 >>>>>>>> --- a/mm/memory.c >>>>>>>> +++ b/mm/memory.c >>>>>>> >>>>>>> >>>>>>> >>>>>>>> @@ -5345,10 +5343,13 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) >>>>>>>> else >>>>>>>> last_cpupid = folio_last_cpupid(folio); >>>>>>>> target_nid = numa_migrate_prep(folio, vmf, vmf->address, nid, &flags); >>>>>>>> - if (target_nid == NUMA_NO_NODE) { >>>>>>>> - folio_put(folio); >>>>>>>> + if (target_nid == NUMA_NO_NODE) >>>>>>>> + goto out_map; >>>>>>>> + if (migrate_misplaced_folio_prepare(folio, vma, target_nid)) { >>>>>>>> + flags |= TNF_MIGRATE_FAIL; >>>>>>>> goto out_map; >>>>>>>> } >>>>>>> >>>>>>> These two locations are repeated code, maybe just merge the ifs into >>>>>>> numa_migrate_prep(). Feel free to ignore if you are not going to send >>>>>>> another version. :) >>>>>> >>>>>> I went back and forth a couple of times and >>>>>> >>>>>> a) Didn't want to move numa_migrate_prep() into >>>>>> migrate_misplaced_folio_prepare(), because having that code in >>>>>> mm/migrate.c felt a bit odd. >>>>> >>>>> I agree after checking the actual code, since the code is just >>>>> updating NUMA fault stats and checking where the folio should be. >>>>> >>>>>> >>>>>> b) Didn't want to move migrate_misplaced_folio_prepare() because I enjoy >>>>>> seeing the migrate_misplaced_folio_prepare() and >>>>>> migrate_misplaced_folio() calls in the same callercontext. >>>>>> >>>>>> I also considered renaming numa_migrate_prep(), but wasn't really able to come up with a good name. >>>>> >>>>> How about numa_migrate_check()? Since it tells whether a folio should be >>>>> migrated or not. >>>>> >>>>>> >>>>>> But maybe a) is not too bad? >>>>>> >>>>>> We'd have migrate_misplaced_folio_prepare() consume &flags and &target_nid, and perform the "flags |= TNF_MIGRATE_FAIL;" internally. >>>>>> >>>>>> What would be your take? >>>>> >>>>> I would either rename numa_migrate_prep() or just do nothing. I have to admit >>>>> that the "prep" and "prepare" in both function names motivated me to propose >>>>> the merge, but now the actual code tells me they should be separate. >>>> >>>> Let's leave it like that for now. Renaming to numa_migrate_check() makes >>>> sense, and likely moving more numa handling stuff in there. >>>> >>>> Bit I yet have to figure out why some of the memory.c vs. huge_memory.c >>>> code differences exist, so we can unify them. >>>> >>>> For example, why did 33024536bafd9 introduce slightly different >>>> last_cpupid handling in do_huge_pmd_numa_page(), whereby it seems like >>>> some subtle difference in handling NUMA_BALANCING_MEMORY_TIERING? Maybe >>>> I am missing something obvious. :) >>> >>> It seems to me that a sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING >>> check is missing in do_huge_pmd_numa_page(). So the >>> >>> if (node_is_toptier(nid)) >>> >>> should be >>> >>> if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) || >>> node_is_toptier(nid)) >>> >>> to be consistent with other checks. Add Ying to confirm. >> >> Yes. It should be so. Sorry for my mistake and confusing. > > Thank you for the confirmation. > >> >>> I also think a function like >>> >>> bool folio_has_cpupid(folio) >>> { >>> return !(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) >>> || node_is_toptier(folio_nid(folio)); >>> } >>> >>> would be better than the existing checks. >> >> Yes. This looks better. Even better, we can add some comments to the >> function too. > > I will prepare a patch about it. Do you have capacity to further consolidate the logic, maybe moving more stuff into the numa_migrate_prep (and renaming it? :)). -- Cheers, David / dhildenb