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[70.82.104.228]) by smtp.gmail.com with ESMTPSA id g18-v6sm6021128qtg.59.2018.06.22.09.28.18 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 22 Jun 2018 09:28:18 -0700 (PDT) Date: Fri, 22 Jun 2018 12:28:17 -0400 (EDT) From: Nicolas Pitre To: Alan Cox cc: Adam Borowski , Dave Mielke , Greg Kroah-Hartman , Samuel Thibault , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/4] have the vt console preserve unicode characters In-Reply-To: <20180622165927.68679862@alans-desktop> Message-ID: References: <20180617190706.14614-1-nicolas.pitre@linaro.org> <20180619130953.bxil552igfkckjmr@angband.pl> <20180621014317.ebslk3gwvpq3k6sq@angband.pl> <20180621022137.GB18453@beta.private.mielke.cc> <20180622015445.7r5u5nn6ofhd4k57@angband.pl> <20180622165927.68679862@alans-desktop> User-Agent: Alpine 2.21 (LFD 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 22 Jun 2018, Alan Cox wrote: > > The other point is a quite pointless assumption that existing scrollback is > > "optimized". Even vgacon mostly uses software scrollback these days, as the > > amount of VGA display memory is really small. > > All of our console driver code is horribly unoptimized for most of > todays hardware. Long ago I did look at what was needed but it's a > seriously non-trivial change. In particular > > - Console I/O occurs under enough locks to keep fort knox safe. That > means it's very very hard to accelerate > > - The logic is plain wrong for a lot of modern video. We shouldn't be > scrolling, we should be rendering the current backing text buffer at > video refresh rate or similar and if the source of the updates outruns > us it doesn't matter - we don't have to draw all the glyphs as if we > were fast enough they would have been a blur anyway. My executive summary from what you say is that there is no longer an advantage to maintain a central vga-style glyph buffer in the core console code, right? Nicolas