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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: bc3bc4kwbm6acataogs65pm3u61kzxrt X-Rspamd-Queue-Id: 1C4BB100007 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1725194922-57594 X-HE-Meta: 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 zGWFNHER rZxeUVEXYmu5qXOq3FoT0k258kd7bQvOl/+j67oDi7zKJHDPLdjDPShw03CZ8MK8WmnUTg4JGSHKtoaZnLuChuORVSzFhamo0BkAA4MfVvdigA3xGfGDwM8GEmW/vRgV657aZ6t8gSmTt8jkCWBKKew7Tzi0FhwnwHhDAYeVtz2guXGxCwuFDXnwjdvLl5C3PW5AWz3FuaSGjiHk6gQpeCNoe+ckzuJWxEOrCA8eK7ksKeppUPv1xgRd6WYVZK17WkHVSyrcp/787NfwtbOTonZ+q6qXsCG8ra8Dtd50fZhtQcWmc77fMNgLuF+qFOv4ca2Ez54pnLxnfvIaeYGLZBQ9IEXXTC2Yb4D2zHGbPbdyfzHv5T8D8H1L3N16qhb1CByhiUO681yE6hBoGJOMwJ1G2AaVwg95se8NhjRzrTaGW5LJQST+umd/6Hw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.060507, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: hi, Usama On 2024/8/22 3:04, Usama Arif wrote: > > On 20/08/2024 17:30, Barry Song wrote: > >> Hi Usama, >> thanks! I can't judge if we need this partially_mapped flag. but if we >> need, the code >> looks correct to me. I'd like to leave this to David and other experts to ack. >> > Thanks for the reviews! > >> an alternative approach might be two lists? one for entirely_mapped, >> the other one >> for split_deferred. also seems ugly ? >> > That was my very first prototype! I shifted to using a bool which I sent in v1, and then a bit in _flags_1 as David suggested. I believe a bit in _flags_1 is the best way forward, as it leaves the most space in folio for future work. > >> On the other hand, when we want to extend your patchset to mTHP other than PMD- >> order, will the only deferred_list create huge lock contention while >> adding or removing >> folios from it? >> > Yes, I would imagine so. the deferred_split_queue is per memcg/node, so that helps. > > Also, this work is tied to khugepaged. So would need some thought when doing it for mTHP. > > I would imagine doing underused shrinker for mTHP would be less beneficial compared to doing it for 2M THP. But probably needs experimentation. > > Thanks Below is the core code snippet to support "split underused mTHP". Can we extend the khugepaged_max_ptes_none value to mthp and keep its semantics unchanged? With a small modification, Only folios with page numbers greater than khugepaged_max_ptes_none - 1 can be added to the deferred_split list and can be split. What do you think? diff --git a/mm/memory.c b/mm/memory.c index b95fce7d190f..ef503958d6a0 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4789,6 +4789,8 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) } folio_ref_add(folio, nr_pages - 1); + if (nr_pages > 1 && nr_pages > khugepaged_max_ptes_none - 1) + deferred_split_folio(folio, false); add_mm_counter(vma->vm_mm, MM_ANONPAGES, nr_pages); count_mthp_stat(folio_order(folio), MTHP_STAT_ANON_FAULT_ALLOC); folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE); shmem THP has the same memory expansion problem when the shmem_enabled configuration is set to always. In my opinion, it is necessary to support "split underused shmem THP", but I am not sure if there is any gap in the implementation? Bang Thanks