From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 2 Jun 2001 17:36:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 2 Jun 2001 17:36:23 -0400 Received: from cisco7500-mainGW.gts.cz ([194.213.32.131]:2564 "EHLO bug.ucw.cz") by vger.kernel.org with ESMTP id ; Sat, 2 Jun 2001 17:36:18 -0400 Message-ID: <20010602105249.A979@bug.ucw.cz> Date: Sat, 2 Jun 2001 10:52:49 +0200 From: Pavel Machek To: kernel list Subject: Reading from /dev/fb0 very slow? Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.93i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! I did some benchmarks, and my framebuffer is *way* faster when writing than when reading: root@bug:/home/pavel# time cat /tmp/test > /dev/fb0 0.01user 0.08system 0.09 (0m0.097s) elapsed 93.13%CPU root@bug:/home/pavel# time cat /dev/fb0 > /dev/null 0.00user 0.62system 0.62 (0m0.620s) elapsed 99.93%CPU root@bug:/home/pavel# That is 6 times slower! This is also very visible in X, where moving regions is expensive, while just drawing regions is fast. For example gnome-terminal is *way* faster *with* transparent background option. Any idea why such assymetry? [This is toshiba 4030cdt with vesafb and 2.4.5] Pavel -- I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care." Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org