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 17:42:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 2 Jun 2001 17:42:33 -0400 Received: from panic.ohr.gatech.edu ([130.207.47.194]:50091 "HELO havoc.gtf.org") by vger.kernel.org with SMTP id ; Sat, 2 Jun 2001 17:42:31 -0400 Message-ID: <3B195DC3.EE919B3F@mandrakesoft.com> Date: Sat, 02 Jun 2001 17:42:27 -0400 From: Jeff Garzik Organization: MandrakeSoft X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.5 i686) X-Accept-Language: en MIME-Version: 1.0 To: Pavel Machek Cc: kernel list Subject: Re: Reading from /dev/fb0 very slow? In-Reply-To: <20010602105249.A979@bug.ucw.cz> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Pavel Machek wrote: > > 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] Do you have write combining enabled? -- Jeff Garzik | Echelon words of the day, from The Register: Building 1024 | FRU Lebed HALO Spetznaz Al Amn al-Askari Glock 26 MandrakeSoft | Steak Knife Kill the President anarchy echelon | nuclear assassinate Roswell Waco World Trade Center