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[209.132.183.28]) by mx.google.com with ESMTPS id n85si207270qkl.139.2019.03.11.00.13.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Mar 2019 00:13:28 -0700 (PDT) Received-SPF: pass (google.com: domain of jasowang@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jasowang@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jasowang@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id BEF7630832CF; Mon, 11 Mar 2019 07:13:27 +0000 (UTC) Received: from [10.72.12.54] (ovpn-12-54.pek2.redhat.com [10.72.12.54]) by smtp.corp.redhat.com (Postfix) with ESMTP id 288C75DA27; Mon, 11 Mar 2019 07:13:18 +0000 (UTC) Subject: Re: [RFC PATCH V2 0/5] vhost: accelerate metadata access through vmap() To: Christoph Hellwig Cc: mst@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, peterx@redhat.com, linux-mm@kvack.org, aarcange@redhat.com, linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kernel.org References: <1551856692-3384-1-git-send-email-jasowang@redhat.com> <20190308141220.GA21082@infradead.org> From: Jason Wang Message-ID: <56374231-7ba7-0227-8d6d-4d968d71b4d6@redhat.com> Date: Mon, 11 Mar 2019 15:13:17 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190308141220.GA21082@infradead.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Mon, 11 Mar 2019 07:13:28 +0000 (UTC) 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: On 2019/3/8 下午10:12, Christoph Hellwig wrote: > On Wed, Mar 06, 2019 at 02:18:07AM -0500, Jason Wang wrote: >> This series tries to access virtqueue metadata through kernel virtual >> address instead of copy_user() friends since they had too much >> overheads like checks, spec barriers or even hardware feature >> toggling. This is done through setup kernel address through vmap() and >> resigter MMU notifier for invalidation. >> >> Test shows about 24% improvement on TX PPS. TCP_STREAM doesn't see >> obvious improvement. > How is this going to work for CPUs with virtually tagged caches? Anything different that you worry? I can have a test but do you know any archs that use virtual tag cache? Thanks