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[87.161.162.111]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b79c469319sm18864766f8f.54.2025.08.05.05.58.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 Aug 2025 05:58:44 -0700 (PDT) Message-ID: Date: Tue, 5 Aug 2025 14:58:42 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [v2 01/11] mm/zone_device: support large zone device private folios To: Balbir Singh , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Karol Herbst , Lyude Paul , Danilo Krummrich , David Airlie , Simona Vetter , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Shuah Khan , Barry Song , Baolin Wang , Ryan Roberts , Matthew Wilcox , Peter Xu , Zi Yan , Kefeng Wang , Jane Chu , Alistair Popple , Donet Tom , Ralph Campbell , =?UTF-8?Q?Mika_Penttil=C3=A4?= , Matthew Brost , Francois Dugast References: <20250730092139.3890844-1-balbirs@nvidia.com> <20250730092139.3890844-2-balbirs@nvidia.com> <1e307223-897c-4db0-9564-95d76bc3d260@nvidia.com> <98a30c7f-8be1-4b08-955c-724667971288@redhat.com> <9c0ad782-e1c3-4c7d-bb20-730d2f915dd5@nvidia.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 22913180002 X-Stat-Signature: 1rwoosgwofub891o93e1ni97o3wert19 X-Rspam-User: X-HE-Tag: 1754398727-283727 X-HE-Meta: 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 Mx3GO7x1 YwQh7ew6xZOvtiySjsw2Il8efeOcSBBMiFNHM1igLtvzTxG1U7sybTXNk2zc+UiXTD55bPSAgoqRKVifAf9cLKY3IxoyRBDDYvplWnvr6LZBHCPZTsK08hx9GjIbOGnAPcR1b0ClWGRoWA11V5WNdayrDxfhC1XnKK6bGrXbRkNDC1q7ye+zbwzCMEQ93bVVdSPWcE9i9N97/HPhWNzGbjlS6j/l+tG0BOqz4vpeKKKm8aAGTLTXYhvViiQECWcrfc7utCA4y9L4qcNs+oj/hZrPTTqI3hp1EL8dtYsrx+5J1ALzn9GF36afLMS9hGafeSs6f9RKd9+VaqYd+YIJXfvnZSvEUR5LdLomi5copbwUnaz3hsE1leKWYLaIRMsSi1nwfZYPAqfeAftF0GpXnk6HSoyFwVJUg4OXC0lYfbqGAAErT43bSL/VCzcuXMm4V94BFKD9TVixonVADyg5SGCT/rw== 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 05.08.25 13:01, Balbir Singh wrote: > On 8/5/25 20:57, David Hildenbrand wrote: >> On 05.08.25 06:22, Balbir Singh wrote: >>> On 7/30/25 19:50, David Hildenbrand wrote: >>> >>>> I think I asked that already but maybe missed the reply: Should these folios ever be added to the deferred split queue and is there any value in splitting them under memory pressure in the shrinker? >>>> >>>> My gut feeling is "No", because the buddy cannot make use of these folios, but maybe there is an interesting case where we want that behavior? >>>> >>> >>> I realized I did not answer this >>> >>> deferred_split() is the default action when partial unmaps take place. Anything that does >>> folio_rmap_remove_ptes can cause the folio to be deferred split if it gets partially >>> unmapped. >> >> Right, but it's easy to exclude zone-device folios here. So the real question is: do you want to deal with deferred splits or not? >> >> If not, then just disable it right from the start. >> > > I agree, I was trying to avoid special casing device private folios unless needed to the extent possible By introducing a completely separate split logic :P Jokes aside, we have plenty of zone_device special-casing already, no harm in adding one more folio_is_zone_device() there. Deferred splitting is all weird already that you can call yourself fortunate if you don't have to mess with that for zone-device folios. Again, unless there is a benefit in having it. -- Cheers, David / dhildenb