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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 541B7106FD98 for ; Fri, 13 Mar 2026 07:49:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:MIME-Version: References:In-Reply-To:Subject:Cc:To:From:Message-ID:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=vy6Jq+Kof1R4hh/pYYz6lFAPbgsTKaeWjj2NgPyP4fM=; b=DyPRybSpDzxANdI2YjhcDCJ441 DQDr5OH8qHOOcHVYifdeBuqh1UgtdnXbgSkBr71giLmbTOl7p98scD6tr1XcDHU3dFQqYOwLBesFi ts7sbWrMiUcN5tfFL6VgT0+653v8sCTFqeUok/7ZkIEhZNnyGgLar1WTE0+UVEZtAaQLPYFzj+cKx eylk5fI63IaVRIKpcGsvXzA5tCjVssG9QHr+DcNnML7yjH0eLuU2mHX6R+gclA2WqPrO5rJ/XzwNL SKYKs/cBt2+hHm+KT0e5FDSqqqeEjguCsi9bsEp/aV43QlSJcMjziA8UsqVX799tM/p7rPeaLie+H hqUjeGoQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w0xHF-0000000H78w-3Omh; Fri, 13 Mar 2026 07:49:45 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w0xHD-0000000H78J-2wma for linux-arm-kernel@lists.infradead.org; Fri, 13 Mar 2026 07:49:44 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id F3D3D40939; Fri, 13 Mar 2026 07:49:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D1E58C19421; Fri, 13 Mar 2026 07:49:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773388182; bh=sFZUrzKv67fc+HAAGjD1+qg7UixgAZhNfQpjz4Rb5WY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=s80jX+ud7c8ei8tYtQiDjt1Dqllzj1lYuIFI1/921kSGz4cnViamOpP8g3wZRctF+ z6L5SFuBVnliOdbMVaWTE/u5e9KJ6VP8cHWeOkwyYMb/EwPTJAKOUkp0JyhfexcgyH V8hZf0W+Qd8jf7ySZJIxprYzpr2EM1MgMJNVF+RvJfAvWBW3bLSHZzLcGG7Vud4cIj uT1hSS2iDpzMBKwOjuPnVk+AwWhNn8CYXyfoOKtvHG2F2ERqAtchhr8Znr72c/1r0Z F3pz5U8p4126EdLpNljxK6AMh6vrAGNskyAAHS4QUe/waY4EYNTLtxVklwLSsgX13S zhsgfbrlKZglQ== Received: from 82-132-235-41.dab.02.net ([82.132.235.41] helo=lobster-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1w0xH2-00000001ZJJ-1eE3; Fri, 13 Mar 2026 07:49:32 +0000 Date: Fri, 13 Mar 2026 07:49:30 +0000 Message-ID: <87qzpocgol.wl-maz@kernel.org> From: Marc Zyngier To: Zhou Wang Cc: , , , jiangkunkun , "xuwei\ (O)" , "Zengtao (B)" Subject: Re: Question about ARM KVM stage2 contiguous bit support for contiguous hugetlb In-Reply-To: <704b6126-f1ad-4d8a-5709-a12e4c8c79ca@hisilicon.com> References: <704b6126-f1ad-4d8a-5709-a12e4c8c79ca@hisilicon.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 82.132.235.41 X-SA-Exim-Rcpt-To: wangzhou1@hisilicon.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, tangnianyao@huawei.com, jiangkunkun@huawei.com, xuwei5@huawei.com, prime.zeng@hisilicon.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260313_004943_759121_86F51B21 X-CRM114-Status: GOOD ( 12.82 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 13 Mar 2026 07:09:40 +0000, Zhou Wang wrote: > > And do we have any plan to support this? Not really. Configurations that are looking at extracting the best possible performance use large mappings at S2 (hugetlbfs). I'm not convinced that there is a strong use-case for dealing with the contiguous hint at S2 when backed by anonymous memory. If you're not under memory pressure, THP already gives you the uplift you want. If you are under memory pressure, you're unlikely to get the contiguity you want. Additionally, dealing with the contiguous hint is a real pain. If you are undertaking this work, please make sure to provide reproducible benchmarks and results that show a definite improvement on the majority of workloads. Thanks, M. -- Jazz isn't dead. It just smells funny.