From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: Re: [PATCH] kvm tools, ui: Optimize SDL updates Date: Sat, 04 Jun 2011 15:04:16 +0300 Message-ID: <1307189056.7239.9.camel@lappy> References: <1307136023-16693-1-git-send-email-penberg@kernel.org> <20110604095451.GA15349@elte.hu> <11EB6DEC-41E9-4C0A-A057-7E88EBA2A008@suse.de> <20110604104245.GF16292@elte.hu> <34B8A15A-AEF2-4E2D-99F5-0EDB41447C31@suse.de> <20110604105443.GH16292@elte.hu> <20110604115353.GA30593@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Alexander Graf , Pekka Enberg , KVM list , Cyrill Gorcunov , John Floren , Gerd Hoffmann To: Ingo Molnar Return-path: Received: from mail-ww0-f44.google.com ([74.125.82.44]:36892 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752140Ab1FDMEb (ORCPT ); Sat, 4 Jun 2011 08:04:31 -0400 Received: by wwa36 with SMTP id 36so2445217wwa.1 for ; Sat, 04 Jun 2011 05:04:30 -0700 (PDT) In-Reply-To: <20110604115353.GA30593@elte.hu> Sender: kvm-owner@vger.kernel.org List-ID: On Sat, 2011-06-04 at 13:53 +0200, Ingo Molnar wrote: > * Alexander Graf wrote: > > > Why would you need panning/scrolling for a fast FB? It's really an > > optimization that helps a lot with VNC, but on local machines or > > SDL you shouldn't see a major difference. > > Qemu's fb console scrolling graphics is pretty slow to me even > locally so i assume that the dirty bitmap trick is not enough. > > VirtualBox graphics is very fast, but it probably has its own console > abstraction and scrolling/2D/3D acceleration. > > Also, since tools/kvm/ is really also about learning interesting > stuff, smooth scrolling was the historic first 'acceleration' usecase > that video graphics cards added - before they evolved more complex 2D > acceleration and then started doing 3D. > > Walking that path would allow us to do a gradual approach, while > still having relevant functionality and enhancements at every step. > > > Unless you use the FB as MMIO. Qemu just maps the FB as RAM and > > checks for dirty bitmap updates periodically. That way you don't > > constantly exit due to MMIO and are good on speed. The slowness you > > describe sounds a lot as if you don't do that trick. > > Correct, and i assumed we already do the dirty-bitmap trick: > > KVM_MEM_LOG_DIRTY_PAGES > KVM_GET_DIRTY_LOG > > But you are right, we do not actually do that! > > Pekka, i think this should be the next step. We'll need scrolling > after that ... > > In theory it would also be nice to tunnel the VGA text frame buffer > over to the KVM tool - as serial console is not supported by most > installers and default distro images. We could actually do a rather > good job of emulating it via Slang/Curses. I doubt we could use dirty pages because unless guest VESA driver supports panning, it will redraw the entire FB - which means that all pages will be dirty. -- Sasha.