From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8A8DC2EEE89 for ; Tue, 28 Jul 2026 20:49:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=96.67.55.147 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785271794; cv=none; b=Gbjw9mkcQ4C17DtBntX2rT45j0um2ZMeJBDtm4SWq3rpNbDon5UngVP4aSmrc8F2TL1YW+GnimXvPgbj4eg9mOxk8ilNT/tGsKB1htal/Jlg82XxHArkPQhjGvAX5RlrsndJzDcPGo65q0vuPQE+Ua9hVuNABmK1NbWJyP8v4DI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785271794; c=relaxed/simple; bh=UkQ4XkjcAKn8Afp/MQTA/Kyck9EcWtucG4G19yGBUvI=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=QAq9O+EDR1w9yzeS6FH5NDnv/7Q/LdH7hF72Y7oO4l2NiTmGf/1KLFbC8o0EcXwdsS76bF5ZEXfoPziJ7m+6dYfB911pyuJc0OkTS+xub/y8alPeKUYMjuNUE2JwBfhQBIyR7+eUWjvJtoFX6u6u5tOkaQwb1rx2ZVNjp2DWhGY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=surriel.com; spf=pass smtp.mailfrom=surriel.com; dkim=pass (2048-bit key) header.d=surriel.com header.i=@surriel.com header.b=LV484WKa; arc=none smtp.client-ip=96.67.55.147 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=surriel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=surriel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=surriel.com header.i=@surriel.com header.b="LV484WKa" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=surriel.com ; s=mail; h=MIME-Version:Content-Transfer-Encoding:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=UkQ4XkjcAKn8Afp/MQTA/Kyck9EcWtucG4G19yGBUvI=; b=LV484WKaTl8ZyE9nOCG8Y+cPnw KACPsrtTbHh/vMxSpu/G7fuilxR8WelJ3hSVD2S9SJnroBXA8GrHjS73QqVp7W2N53PGGuYo7MbE0 GVOwcUPiZkDpPPVsR07g+L5szrpq57wqTGgv3/QWfiUCk4neOfrsOmfpGSpCSmUFe2BxKtpCmXhYf H+df/lwNXKEw2S+swbV9ROBLeKGHho3Tu7KQEFQ/OdhUpwEacL07xt4Yn1z4jsoHgseWEbdGF/8z6 WkJMJ3skbpaHex3jTDQIQCLl6h4lU7Ouj3nrlwu5WOaTWKe7zAjgyvlch4mzCa1Q0I6lx3fQeE4d5 ibAk+kEA==; Received: from fangorn.home.surriel.com ([10.0.13.7]) by shelob.surriel.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.97.1) (envelope-from ) id 1woojv-000000000ft-1j7X; Tue, 28 Jul 2026 16:49:27 -0400 Message-ID: <8953b9172e8e2c6f418b40f464392d4e498c82db.camel@surriel.com> Subject: Re: [PATCH RFC v4 11/12] mm/gup: batch contiguous PTE-mapped large folios in follow_page_mask() From: Rik van Riel To: "David Hildenbrand (Arm)" , Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com, Dave Hansen , Peter Zijlstra , Suren Baghdasaryan , Lorenzo Stoakes , Vlastimil Babka , "Liam R. Howlett" , Mike Rapoport , Michal Hocko , Jason Gunthorpe , John Hubbard , Peter Xu , Matthew Wilcox , Usama Arif Date: Tue, 28 Jul 2026 16:49:27 -0400 In-Reply-To: <7fbdb447-3d6c-4071-bc6d-1af4e44cbd7f@kernel.org> References: <20260724222934.1463812-1-riel@surriel.com> <20260724222934.1463812-12-riel@surriel.com> <5490f8b1-d611-4e4d-bd8b-19c0e05698a3@kernel.org> <7fbdb447-3d6c-4071-bc6d-1af4e44cbd7f@kernel.org> Autocrypt: addr=riel@surriel.com; prefer-encrypt=mutual; keydata=mQENBFIt3aUBCADCK0LicyCYyMa0E1lodCDUBf6G+6C5UXKG1jEYwQu49cc/gUBTTk33A eo2hjn4JinVaPF3zfZprnKMEGGv4dHvEOCPWiNhlz5RtqH3SKJllq2dpeMS9RqbMvDA36rlJIIo47 Z/nl6IA8MDhSqyqdnTY8z7LnQHqq16jAqwo7Ll9qALXz4yG1ZdSCmo80VPetBZZPw7WMjo+1hByv/ lvdFnLfiQ52tayuuC1r9x2qZ/SYWd2M4p/f5CLmvG9UcnkbYFsKWz8bwOBWKg1PQcaYHLx06sHGdY dIDaeVvkIfMFwAprSo5EFU+aes2VB2ZjugOTbkkW2aPSWTRsBhPHhV6dABEBAAG0HlJpayB2YW4gU mllbCA8cmllbEByZWRoYXQuY29tPokBHwQwAQIACQUCW5LcVgIdIAAKCRDOed6ShMTeg05SB/986o gEgdq4byrtaBQKFg5LWfd8e+h+QzLOg/T8mSS3dJzFXe5JBOfvYg7Bj47xXi9I5sM+I9Lu9+1XVb/ r2rGJrU1DwA09TnmyFtK76bgMF0sBEh1ECILYNQTEIemzNFwOWLZZlEhZFRJsZyX+mtEp/WQIygHV WjwuP69VJw+fPQvLOGn4j8W9QXuvhha7u1QJ7mYx4dLGHrZlHdwDsqpvWsW+3rsIqs1BBe5/Itz9o 6y9gLNtQzwmSDioV8KhF85VmYInslhv5tUtMEppfdTLyX4SUKh8ftNIVmH9mXyRCZclSoa6IMd635 Jq1Pj2/Lp64tOzSvN5Y9zaiCc5FucXtB9SaWsgdmFuIFJpZWwgPHJpZWxAc3VycmllbC5jb20+iQE +BBMBAgAoBQJSLd2lAhsjBQkSzAMABgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRDOed6ShMTe g4PpB/0ZivKYFt0LaB22ssWUrBoeNWCP1NY/lkq2QbPhR3agLB7ZXI97PF2z/5QD9Fuy/FD/jddPx KRTvFCtHcEzTOcFjBmf52uqgt3U40H9GM++0IM0yHusd9EzlaWsbp09vsAV2DwdqS69x9RPbvE/Ne fO5subhocH76okcF/aQiQ+oj2j6LJZGBJBVigOHg+4zyzdDgKM+jp0bvDI51KQ4XfxV593OhvkS3z 3FPx0CE7l62WhWrieHyBblqvkTYgJ6dq4bsYpqxxGJOkQ47WpEUx6onH+rImWmPJbSYGhwBzTo0Mm G1Nb1qGPG+mTrSmJjDRxrwf1zjmYqQreWVSFEt26tBpSaWsgdmFuIFJpZWwgPHJpZWxAZmIuY29tP okBPgQTAQIAKAUCW5LbiAIbIwUJEswDAAYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQznneko TE3oOUEQgAsrGxjTC1bGtZyuvyQPcXclap11Ogib6rQywGYu6/Mnkbd6hbyY3wpdyQii/cas2S44N cQj8HkGv91JLVE24/Wt0gITPCH3rLVJJDGQxprHTVDs1t1RAbsbp0XTksZPCNWDGYIBo2aHDwErhI omYQ0Xluo1WBtH/UmHgirHvclsou1Ks9jyTxiPyUKRfae7GNOFiX99+ZlB27P3t8CjtSO831Ij0Ip QrfooZ21YVlUKw0Wy6Ll8EyefyrEYSh8KTm8dQj4O7xxvdg865TLeLpho5PwDRF+/mR3qi8CdGbkE c4pYZQO8UDXUN4S+pe0aTeTqlYw8rRHWF9TnvtpcNzZw== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2026-07-28 at 21:05 +0200, David Hildenbrand (Arm) wrote: > On 7/28/26 02:37, Rik van Riel wrote: > > On Mon, 2026-07-27 at 15:54 +0200, David Hildenbrand (Arm) wrote: > > > On 7/25/26 00:29, Rik van Riel wrote: > > > >=20 > > > > =C2=A0 gup_test -L -m 256 -n 65536 -r 16 -t > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 be= fore=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 after > > > > =C2=A0 64 kB mTHP=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0 3140 us=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 412 us=C2=A0=C2=A0= (7.6x) > > > > =C2=A0 2 MB THP (control)=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 78 us=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 76 us > > > > =C2=A0 4 kB base (control)=C2=A0=C2=A0 3010 us=C2=A0=C2=A0=C2=A0=C2= =A0 3042 us > > > >=20 > > > > The PMD-mapped 2 MB THP already returns the whole mapping in > > > > one > > > > step, so > > > > it stays fast and unchanged. The 4 kB baseline shows the per- > > > > page > > > > walk cost > > > > that the 64 kB case paid before this change; only the PTE- > > > > mapped > > > > large > > > > folio case improves. > > > >=20 > > > > Assisted-by: Claude:claude-opus-4.8 > > > > Signed-off-by: Rik van Riel > > >=20 > > > Why is this patch part of this patch set? > > >=20 > > > This makes perfect sense independently, no? > >=20 > > I'm happy to drop this for now. I think it would > > fit in better with another optimization to only > > take one refcount per continuously mapped extent > > of pages from the same folio. > >=20 > > I can't really untangle it because it modifies > > some of the same code as other patches in the > > series, but I'm happy to save it for a follow-up. >=20 > Given this series here is RFC, can't we have that optimization > upfront? I'd > assume it will benefit quite some use cases that pin multiple > consecutive pages. >=20 > IIUC, it'd be mostly patch 10+11. No need to worry about the test > case right > now, we can do that later. I'm happy to send patches 10-11 by themselves. We can save a self test for after the future optimization of only taking a single refcount for an entire extent of pages from the same folio mapped in the same process, at which point we'll have something more serious to test. I'll get these to you soon. --=20 All Rights Reversed.