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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 694BCC43144 for ; Fri, 22 Jun 2018 15:59:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D16D324553 for ; Fri, 22 Jun 2018 15:59:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D16D324553 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lxorguk.ukuu.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934157AbeFVP7u (ORCPT ); Fri, 22 Jun 2018 11:59:50 -0400 Received: from www.llwyncelyn.cymru ([82.70.14.225]:60328 "EHLO fuzix.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933853AbeFVP7s (ORCPT ); Fri, 22 Jun 2018 11:59:48 -0400 Received: from alans-desktop (82-70-14-226.dsl.in-addr.zen.co.uk [82.70.14.226]) by fuzix.org (8.15.2/8.15.2) with ESMTP id w5MFxSrn000784; Fri, 22 Jun 2018 16:59:28 +0100 Date: Fri, 22 Jun 2018 16:59:27 +0100 From: Alan Cox To: Adam Borowski Cc: Dave Mielke , Nicolas Pitre , Greg Kroah-Hartman , Samuel Thibault , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/4] have the vt console preserve unicode characters Message-ID: <20180622165927.68679862@alans-desktop> In-Reply-To: <20180622015445.7r5u5nn6ofhd4k57@angband.pl> 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> Organization: Intel Corporation X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > 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. > I don't know much about console display drivers in general, though, and it > looks like most of them are unmaintained (just noticed that sisusb for > example hasn't seen a maintainer action for 13 years, and that person's > domain expired in 2006). There has been some work on them but they are not in a good state, and as a result we have problems like these as well as the inability to nicely support multi-console systems except in Wayland/X. Alan