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Wong" , mcgrof@kernel.org, gost.dev@samsung.com, hch@lst.de, Pankaj Raghav Subject: Re: [PATCH v3 0/5] add persistent huge zero folio support Message-ID: References: <20250811084113.647267-1-kernel@pankajraghav.com> <112b4bcd-230a-4482-ae2e-67fa22b3596f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <112b4bcd-230a-4482-ae2e-67fa22b3596f@redhat.com> X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6880C180005 X-Stat-Signature: 3b5i1pkyaa1b73red9fe8y4y4dxdigei X-HE-Tag: 1754907154-54268 X-HE-Meta: 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 ZRCgCJz1 26/npi8Ni7yYsQ1z2dVlk4KqybTrKFCYNU6fcGhNNYLODv+hhrgxg5XwIhYGf1oSPbPn7ZxN31Q0DcZPvZyXZlRWw+KWBN/jjT3GA5Sj6os59N0WLoNRrPYFEeyd/oOFaYmO9S+mxCMSs3HzMWKk+IXRoTiHEIuh+RwK7QgXghDksNOYNkRnblRmgsmRl2tlS34WFBUkSYsXVUhg7Q0r8Mr9Uo26zLJxwm44trLjGxVHeT5tSWlQ2MD5Fm76oHqwIYzeL+Hwi4lKR4GdksTqSPCRTJd1CHi8ilSjhCvQAgYjuFIzlPff/88VYsOZPLIavKT8/SH6pqysgqQu7gGseDS6vxM9UPWw6gKrqLtr+ix4Bzrx+dYI8gF7OVA== 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: > > > > Add a config option PERSISTENT_HUGE_ZERO_FOLIO that will always allocate > > > > the huge_zero_folio, and disable the shrinker so that huge_zero_folio is > > > > never freed. > > > > This makes using the huge_zero_folio without having to pass any mm struct and does > > > > not tie the lifetime of the zero folio to anything, making it a drop-in > > > > replacement for ZERO_PAGE. > > > > > > > > I have converted blkdev_issue_zero_pages() as an example as a part of > > > > this series. I also noticed close to 4% performance improvement just by > > > > replacing ZERO_PAGE with persistent huge_zero_folio. > > > > > > > > I will send patches to individual subsystems using the huge_zero_folio > > > > once this gets upstreamed. > > > > > > > > Looking forward to some feedback. > > > > > > Why does it need to be compile-time? Maybe whoever needs huge zero page > > > would just call get_huge_zero_page()/folio() on initialization to get it > > > pinned? > > > > That's what v2 did, and this way here is cleaner. > > Sorry, RFC v2 I think. It got a bit confusing with series names/versions. > Another reason we made it a compile time config is because not all machines would want a PMD sized folio just for zeroing. For example, Dave Hansen told in one of the early revisions that a small x86 VM would not want this. So it is a default N, and it will be an opt-in. -- Pankaj