From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 202E1C61DB9 for ; Tue, 25 Aug 2026 13:37:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D28996B00C3; Tue, 25 Aug 2026 09:37:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CD83D6B00C4; Tue, 25 Aug 2026 09:37:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BA0176B00C5; Tue, 25 Aug 2026 09:37:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 94B586B00C3 for ; Tue, 25 Aug 2026 09:37:44 -0400 (EDT) Received: from smtpin28.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 06C18160425 for ; Tue, 25 Aug 2026 13:37:44 +0000 (UTC) X-FDA: 85139894448.28.C016BAE Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) by imf30.hostedemail.com (Postfix) with ESMTP id 4BAF880009 for ; Tue, 25 Aug 2026 13:37:41 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=surriel.com header.s=mail header.b="nJtI+U +"; spf=pass (imf30.hostedemail.com: domain of riel@surriel.com designates 96.67.55.147 as permitted sender) smtp.mailfrom=riel@surriel.com; dmarc=pass (policy=quarantine) header.from=surriel.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787665062; b=aN6OOMuRyjCpqV2zXhriF5j0pd4jyN15u1/8I8c7aRXG96gkvGvRYqPQbvxk/0jUyULgfP f0N97EfvuG2MGNtDPYJwXPrMC+o344FkTxZwz0h1SSfvLCEYpAswa4kiy2LBE3o0lDY7sL aJmPL2thEXeIZdzso6RfEXWmnb0SnWE= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=surriel.com header.s=mail header.b="nJtI+U +"; spf=pass (imf30.hostedemail.com: domain of riel@surriel.com designates 96.67.55.147 as permitted sender) smtp.mailfrom=riel@surriel.com; dmarc=pass (policy=quarantine) header.from=surriel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787665062; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=pCW1SrRc9TdfDbK0btXS320EQf/SwGeEdsMu8TkCBi8=; b=wucxDPMfY+pgjcYSpdZKmNN/s5DKt9BAnQ5Psv7E+VyxXTwLx8znNmO0nn0ITal6ycYtnS YiC6rvHRzlOAThXxkCu8v8H36ohsP75b17EC78RyuXOOOLqRqMOMohpLSEL1/ww51FKTKw oKm88JpjhZrZTXiCf9QRRGy9xWC9f2o= 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; bh=pCW1SrRc9TdfDbK0btXS320EQf/SwGeEdsMu8TkCBi8=; b=nJtI+U +skEo/xtAPNWY+Pt/aZ55afKPl/U9qwxu+GZvWaL5oKWwGKHChMkl63naXjMRF2NPMrgEL7jQVnlV TySRY2nVE/aCJMdcjOg/HlwxXqaZ6Z/toX9y/ZxkkX4sIx4yHSWwjPn299Pi1FA/wiM2L8rO9nX3s hS7eRw4ernxPTnRFK+9WX9POFKleZjBl2H6VWZXjlofGHuB1x935cNJEoeeU17LoTsXeXZ0lcXHda 5nuQwE9GjbSrgwtGgEla/eG2pfXC4B1Lf+MtEDqedKHUyeQWPsvfOQrJfjLG0Zcc4uG0UFv7XJfIP xEx7O6lFYT5rhZpAgxLbn8pW7GvQ==; Received: from [2601:18c:8100:a0e0:5a47:caff:fe78:8708] by shelob.surriel.com with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.99.5) (envelope-from ) id 1wyrKv-00000004DAx-1RiJ; Tue, 25 Aug 2026 13:37:09 +0000 Message-ID: Subject: Re: [RFC PATCH v3 0/8] batch lookups in follow_page_mask() From: Rik van Riel To: Christoph Hellwig Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, Andrew Morton , David Hildenbrand , Jason Gunthorpe , John Hubbard , Peter Xu , linux-mm@kvack.org Date: Tue, 25 Aug 2026 09:37:09 -0400 In-Reply-To: References: <20260811025157.1632867-1-riel@surriel.com> 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 3.60.2 (3.60.2-1.fc44) MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 4BAF880009 X-Stat-Signature: hnhcc57uxjkh4ku4mp9z9jrmzgs1pypr X-HE-Tag: 1787665061-468959 X-HE-Meta: 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 1JeqbGSa SpPHNQtIOflKx5tMKLpJQtLhX66wuZkMUXNWkyimih0NQI/ChJTiO0Y+2xK0/xTeGb0j2rwLFf/pspzTl22BKysN7mDtdgkTTVhOxU9dNZS4vfRI25krvwRRIJPzvRwLD+vsree6cAE60rIFVkWhEsFvU8IYSUWMZw1d00FtAJSOlb3H9doFHa0FMo5+LnJBOBvAo6VVQw+neDqMZpLg8jyzv8V7v6eqg9iqMTV6D4VLb/AKPUJldsXSZdpLnNE94BkIN0KDdmq4PzbMH8hheWrwAM3ToS+OVcmPhrMs+pcYYU/8MTkFWuKxMDwcxBgCoTRCk Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 2026-08-25 at 00:52 -0700, Christoph Hellwig wrote: > On Mon, Aug 10, 2026 at 10:51:49PM -0400, Rik van Riel wrote: > > follow_page_mask() walks the page tables one page at a time, even > > when the > > caller asked for a whole run of contiguous pages. Every page of a > > large folio > > re-enters the pmd/pud/pte walk and re-takes the page table lock. > >=20 > > This series changes follow_page_mask() to return a page count and a > > fill an > > array of pages, instead of a single struct page, so a walker can > > hand back > > more than one page per call. >=20 > And what many including the most performance critical callers want > instead is really a single bio_vec.=C2=A0 Maybe we can go the extra step > for > that, as it would reduce the number of calls into gup significantly. >=20 Which code are you referring to here? blk_rq_map_user() seems to end up calling pin_user_pages_fast(), via iov_iter_extract_user_pages, and it directly fills in the bio_vec's pages array. Is there another performance critical path that goes through the slower get_user_pages() path? --=20 All Rights Reversed.