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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id 32si7108127plc.427.2019.03.08.06.12.23 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 08 Mar 2019 06:12:23 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of batv+8598a4c90796d7699c08+5675+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b="l/Cyl8vy"; spf=pass (google.com: best guess record for domain of batv+8598a4c90796d7699c08+5675+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=BATV+8598a4c90796d7699c08+5675+infradead.org+hch@bombadil.srs.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding: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=aQc0SyowOdTmxrkU2xp2xFOofpRQZkuv8UFO0ktx/Gw=; b=l/Cyl8vyTvDwqSnNGu+5hMY12 7QQ4o+sc3edmPS09IezABK15wlZW6k9rwF3gFP+7/jqA5V7RHy5tzk1qtzM8Sndq08YlArFd9CD1Q spSIjJhhR6pcrx90oxnbZBy355+sSdWeMoXu9ObKhzB+bVN0CQaQJhw1I5E8NsutG72MPa5twt1Su cGXv9XQE9XF/lpzlYXjNCJDb3/2462UGi5AyXHq+iSCs+WlNmZowjcaL8sllXycDVE06H2QknUzS2 NSARjQDBHU0ii6zLqLbBouH1vpo+82oU3YYOjM3BaiaW3nITV6H8+e3bdTaIVQx7uP8t2oCVMKvdA BZun3Zvuw==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1h2GEW-0006nZ-PD; Fri, 08 Mar 2019 14:12:20 +0000 Date: Fri, 8 Mar 2019 06:12:20 -0800 From: Christoph Hellwig To: Jason Wang 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 Subject: Re: [RFC PATCH V2 0/5] vhost: accelerate metadata access through vmap() Message-ID: <20190308141220.GA21082@infradead.org> References: <1551856692-3384-1-git-send-email-jasowang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1551856692-3384-1-git-send-email-jasowang@redhat.com> User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html 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 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?