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Wong" , mcgrof@kernel.org, gost.dev@samsung.com, hch@lst.de, Pankaj Raghav Subject: Re: [PATCH 3/5] mm: add static huge zero folio Message-ID: References: <20250804121356.572917-1-kernel@pankajraghav.com> <20250804121356.572917-4-kernel@pankajraghav.com> <4463bc75-486d-4034-a19e-d531bec667e8@lucifer.local> <70049abc-bf79-4d04-a0a8-dd3787195986@redhat.com> <6ff6fc46-49f1-49b0-b7e4-4cb37ec10a57@lucifer.local> <9a657c84-99fe-41ba-88ca-097acab4b96b@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9a657c84-99fe-41ba-88ca-097acab4b96b@redhat.com> X-Rspamd-Queue-Id: 6DD4280004 X-Stat-Signature: cxj58krbjcax7iq1ph5ptfbfg3qncjid X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1754484227-300448 X-HE-Meta: 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 nBec3k8D 7X2kvg8hPhl1Y//Pna/XIaZ6Kts5wuDi5hF1og4ckPij+UjS3YYOaZXrqoVDlQbe4gTO0NuYz1YNZoRyUymgomhisP/2VMNls2tUZ994sGUHjTNP5yI5s7kwfUag1GUXwcW7Ua6v4ePbHeKnUaYJWObsydbdqVfi60aNwFZl6FykJBFISo4jUWGcrg59tdB4EvSRU+dbGfFNqYE2uXRpHHx7h/XE8VVrVjwCEFweY/xbYH8n7TDjE+rCWI2HjiS/X62EOqW4a7dDhA2fRyVKX5HkdIoNJ6jN2yGC1edddobOyJY7zMJidwgDqm2g8u3JVCJun230+Z09ZIlESeILD0zTJ/Q== 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 Wed, Aug 06, 2025 at 02:36:51PM +0200, David Hildenbrand wrote: > On 06.08.25 14:28, Pankaj Raghav (Samsung) wrote: > > On Wed, Aug 06, 2025 at 02:24:28PM +0200, David Hildenbrand wrote: > > > On 06.08.25 14:18, Pankaj Raghav (Samsung) wrote: > > > > > We could go one step further and special case in mm_get_huge_zero_folio() + > > > > > mm_put_huge_zero_folio() on CONFIG_STATIC_HUGE_ZERO_FOLIO. > > > > > > > > > > > > > Hmm, but we could have also failed to allocate even though the option > > > > was enabled. > > > > > > Then we return huge_zero_folio, which is NULL? > > > > > > Or what are you concerned about? > > > > But don't we want to keep the "dynamic" allocation part be present even > > though we failed to allocate it statically in the shrinker_init? > > > > Mainly so that the existing users of mm_get_huge_zero_folio() are not affected by > > these changes. > > I would just keep it simple and say that if we fail the early allocation > (which will be extremely unlikely that early during boot!), just don't ever > try to reallocate, even not when we could through mm_get_huge_zero_folio(). > > That sounds as simple as it gets. Again, failing to allocate that early and > then succeeding to allocate later is a fairly unlikely scenario. Ok. I will also document this as a comment just so that people are aware of this behaviour. Thanks a lot David for the comments and feedback! -- Pankaj Raghav