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,URIBL_BLOCKED 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 08C48C43144 for ; Fri, 22 Jun 2018 17:51:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 74732246E9 for ; Fri, 22 Jun 2018 17:51:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 74732246E9 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 S934125AbeFVRvQ (ORCPT ); Fri, 22 Jun 2018 13:51:16 -0400 Received: from www.llwyncelyn.cymru ([82.70.14.225]:32902 "EHLO fuzix.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933995AbeFVRvP (ORCPT ); Fri, 22 Jun 2018 13:51:15 -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 w5MHp37u004287; Fri, 22 Jun 2018 18:51:03 +0100 Date: Fri, 22 Jun 2018 18:51:03 +0100 From: Alan Cox To: Nicolas Pitre 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 Message-ID: <20180622185103.21a53a66@alans-desktop> In-Reply-To: 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> 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 On Fri, 22 Jun 2018 12:28:17 -0400 (EDT) Nicolas Pitre wrote: > 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? Yeah. The only driver that it suits is the VGA text mode driver, which at 2GHz+ is going to be fast enough whatever format you convert from. We have the memory, the processor power and the fact almost all our displays are bitmapped (or more complex still) all in favour of throwing away that limit. Alan