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Received: from shell.armlinux.org.uk ([2002:4e20:1eda:1:5054:ff:fe00:4ec]:40082) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jhxtQ-0006jA-0t; Sun, 07 Jun 2020 17:11:33 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1jhxtE-0001Dc-K3; Sun, 07 Jun 2020 17:11:16 +0100 Date: Sun, 7 Jun 2020 17:11:16 +0100 From: Russell King - ARM Linux admin To: afzal mohammed Subject: Re: ARM: vmsplit 4g/4g Message-ID: <20200607161116.GN1551@shell.armlinux.org.uk> References: <20200512104758.GA12980@afzalpc> <20200514111755.GA4997@afzalpc> <20200514133545.GA5020@afzalpc> <20200516060624.GA6371@afzalpc> <20200607125932.GA4576@afzalpc> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200607125932.GA4576@afzalpc> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200607_091348_934742_D1F136B2 X-CRM114-Status: GOOD ( 11.00 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Linux ARM , Arnd Bergmann , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sun, Jun 07, 2020 at 06:29:32PM +0530, afzal mohammed wrote: > Hi, > > On Sat, May 16, 2020 at 09:35:57AM +0200, Arnd Bergmann wrote: > > On Sat, May 16, 2020 at 8:06 AM afzal mohammed wrote: > > > > Okay, so the conclusion i take is, > > > 1. VMSPLIT 4G/4G have to live alongside highmem > > > 2. For user space copy, do pinning followed by kmap > > > Right, though kmap_atomic() should be sufficient here > > because it is always a short-lived mapping. > > get_user_pages_fast() followed by kmap_atomic() & then memcpy() seems > to work in principle for user copy. Have you done any performance evaluation of the changes yet? I think it would be a good idea to keep that in the picture. If there's any significant regression, then that will need addressing. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC for 0.8m (est. 1762m) line in suburbia: sync at 13.1Mbps down 424kbps up _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel