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b=gIGAlmpHQ9fwoE8u5/k2Wn6ewPPNyo9bpLGiPfe4Yx+72vLm6jy3DAwys7XWmOEOg 15M9n+MZKpYqs/Y+6o5BAWs1sKgu0bW0Eu5IdGEFNDurK+xU0KP1qVFJyvMBvK68/M jPrkwgtA88YyuCqdOAWWXzZ+yY1fRhniMbb2XgIEy7Qv27ngxo20VY+7bTKEpihvTR Dw2QIZF7BoQh1/2IhaH7Fsk8P2IBw13ZTGVcVnqM5RGQgX0gwp1oNdiO5kvNaWBST5 nY7bgQHPwxk92uwt0LBqbwUGnly3gCXxzd+2svXI4vb4FHgkqAfJBAYyZZwUXNX+QD vIabhJVMgsswA== Message-ID: Date: Mon, 11 May 2026 17:40:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/7] mm/migrate: add batch-copy path in migrate_pages_batch To: Shivank Garg , akpm@linux-foundation.org Cc: kinseyho@google.com, weixugc@google.com, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, willy@infradead.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, dave@stgolabs.net, Jonathan.Cameron@huawei.com, rkodsara@amd.com, vkoul@kernel.org, bharata@amd.com, sj@kernel.org, rientjes@google.com, xuezhengchu@huawei.com, yiannis@zptcorp.com, dave.hansen@intel.com, hannes@cmpxchg.org, jhubbard@nvidia.com, peterx@redhat.com, riel@surriel.com, shakeel.butt@linux.dev, stalexan@redhat.com, tj@kernel.org, nifan.cxl@gmail.com, jic23@kernel.org, aneesh.kumar@kernel.org, nathan.lynch@amd.com, Frank.li@nxp.com, djbw@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260428155043.39251-2-shivankg@amd.com> <20260428155043.39251-10-shivankg@amd.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260428155043.39251-10-shivankg@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: CFA6A4000D X-Rspamd-Server: rspam04 X-Stat-Signature: w3un7sbr95nc3qo5hjnbsc34oy545a1n X-HE-Tag: 1778514068-421339 X-HE-Meta: U2FsdGVkX1+aWncFhnh8X7Dk4YYgG3Troe599kWm8oPP52dbUB5l1pkOZloDvPx9TnG9vnDad9GpVCIxGhszhVzS0hBb3WvRe01ZRRr/kAFyKIubQhgn/GqkDl4ayxGhReZ0AY8L68rFKsnzcVIUONQpsuY6yltlelqSrzWpf/wCq4kCv6jroaGCsInhpoxdT7xJYmMO0uuITxjWdAgN4pZVK2y9UOGOZFcw8LL2qdYY1DVZ9ai+QYYqDAJ9zLjFD2XgdJgg/eNxJBCVbB9V9apIcMqjULLHPJK06QuS/Yy++tqxKpEJ/gyibwRRJacUSyH6qUbX0M54ODRdxgYrSwqoFzVfph0WKHTYTUcEmjlg1XHwTcdL3LRZyIlFYe6LixrieQla0tXXoMwXaIdZSRKAk9gvisFAuDvtGQ21shETulkw16o8innWzYCS2HxWjDxZPZ9glUNlNijyN4yxdVCM702ZqxzwNDcKtgsarLxRPb3OSinuSdKJ/Ige102wgtKC1+1hvnX/A0kEixR+pNypP7o98u8B37D+zQYzmF6cEyOwEVYTaaJf10rP3RX36xdZp56eVN2AWGbp2UsGZ5TxiM3KgW0MdvvOM+Bi6ftsPlNgnlmEulq/E7aiGfaGoyff+ebfioflL1eo82w0GSun3wbwkue+eN3Zb0NNnRdM3ehlsG+U7e3d/2ruhtyIGe+3c0fKxkfVC9Y7Up5GSJQcsxMhm6CECC97uzSV3b1C1McAyTVKBJcX3RXzbDiQcNq/YWqBT2L8upQtRZE0CIR3Zr7wZkxXteo/SPNoUm1hghqi+kLwxd5bJKydcjrvWwhr2Nzin+/337q/zhxEfDQw/4QcRP4aAmLRGor1a33T8aoP6yFOWQtyAvT0uaTMH1reeHxwUQFwvE7z01xMF4hYUid2sJ+0sLeGR+ZI6xJCBR5nhGW2jGNNORI7ifzgvFE3nOySbrqjAY5AI+J P83OI4me Q8nWXfVqkahMEqSJHZ+uptzZmErUxpRKMbx1SCu89Ta/FHr4CnNPau/xrx+++WR/FJqdtOEof0BhaZnQrZ879YCqD/u25mByzRfzgmZNfYH85C+4JJFOvIlECPVi+P3p+6FWavkKSJnZSQ5C6n9kuvtCj7UK0uoA3Owmk4UiNLjPUZ5JGErK5srvy2T8a3IcbxHgdHXLqVFNncauVY4rembxdssopZhC1+jmv4Fr0DzeGFRvdjAVf7GermnW4ap744iZKIvNeudgEK0CTOZAySiZATAPu+Xeq/c4fSnS3Ej74+LkOiUWw+rlWvWeJX3mhDZjnOknKlQJPUZcCgM8XbikCqfxyfE6bR98AHlTEV0Y8LiB/EfwVadzMgGS9hM8Zfm4YybFpv6azlU6urMRmKodjaw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/28/26 17:50, Shivank Garg wrote: > Add folios_mc_copy() which walks list of src and dst folios in lockstep, > and copies folio content via folio_mc_copy(). folios_cnt parameter is > unused here, but is part of the offload_copy callback signature used by > later patches in the series. > > Split unmapped folios into batch-eligible (unmap_batch/dst_batch) and > standard (unmap_single/dst_single) lists, gated by the > migrate_offload_enabled which is off by default. So, when no offload > driver is active, the branch is never taken and everything goes > through the standard path. > > After TLB flush, batch copy the eligible folios via folios_mc_copy() > and pass already_copied=true into migrate_folios_move() so > __migrate_folio() skips the per-folio copy. > > On batch copy failure, already_copied flag stays false and each folio > fall back to individual copy. > > Signed-off-by: Shivank Garg > --- > include/linux/mm.h | 2 ++ > mm/migrate.c | 61 +++++++++++++++++++++++++++++++++++----------- > mm/util.c | 30 +++++++++++++++++++++++ > 3 files changed, 79 insertions(+), 14 deletions(-) [...] > > +DEFINE_STATIC_KEY_FALSE(migrate_offload_enabled); > + > static const struct movable_operations *offline_movable_ops; > static const struct movable_operations *zsmalloc_movable_ops; > > @@ -1724,6 +1727,12 @@ static int migrate_hugetlbs(struct list_head *from, new_folio_t get_new_folio, > return nr_failed; > } > > +/* movable_ops folios have their own migrate path */ > +static bool folio_supports_batch_copy(struct folio *folio) > +{ > + return likely(!page_has_movable_ops(&folio->page)); > +} As these things are not actually folios (and callers will have to be taught to distinguish them way, way earlier), I guess you should make this /* movable_ops pages have a separate migration path */ static bool page_supports_batch_copy(struct page *page) ... > + > static void migrate_folios_move(struct list_head *src_folios, > struct list_head *dst_folios, > free_folio_t put_new_folio, unsigned long private, > @@ -1752,7 +1761,7 @@ static void migrate_folios_move(struct list_head *src_folios, > /* > * The rules are: > * 0: folio will be freed > - * -EAGAIN: stay on the unmap_folios list > + * -EAGAIN: stay on the src_folios list > * Other errno: put on ret_folios list > */ > switch (rc) { [...] > --- a/mm/util.c > +++ b/mm/util.c > @@ -778,6 +778,36 @@ int folio_mc_copy(struct folio *dst, struct folio *src) > } > EXPORT_SYMBOL(folio_mc_copy); > > +/** > + * folios_mc_copy - Copy the contents of list of folios. > + * @dst_list: destination folio list. > + * @src_list: source folio list. > + * @folios_cnt: unused here, present for callback signature compatibility. > + * > + * Walks list of src and dst folios in lockstep and copies folio > + * content via folio_mc_copy(). The caller must ensure both lists have > + * the same number of entries. This may sleep. This *function* > + * > + * Return: 0 on success, negative errno on failure. > + */ > +int folios_mc_copy(struct list_head *dst_list, struct list_head *src_list, > + unsigned int __always_unused folios_cnt) > +{ > + struct folio *src, *dst; > + int ret; > + > + dst = list_first_entry(dst_list, struct folio, lru); > + list_for_each_entry(src, src_list, lru) { > + ret = folio_mc_copy(dst, src); > + if (ret) > + return ret; > + dst = list_next_entry(dst, lru); > + } Wouldn't it be cleaner to remember "already copied" immediately after we ... performed the copy? (succeeded with folio_mc_copy) -- Cheers, David