From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37980) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YwrsL-00071D-3k for qemu-devel@nongnu.org; Mon, 25 May 2015 08:53:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YwrsG-0004WA-4X for qemu-devel@nongnu.org; Mon, 25 May 2015 08:53:01 -0400 Received: from mail-wg0-x22e.google.com ([2a00:1450:400c:c00::22e]:35021) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YwrsF-0004Vv-TA for qemu-devel@nongnu.org; Mon, 25 May 2015 08:52:56 -0400 Received: by wgme6 with SMTP id e6so3908830wgm.2 for ; Mon, 25 May 2015 05:52:54 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <55631B23.3090303@redhat.com> Date: Mon, 25 May 2015 14:52:51 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <555DE2EF.1000509@redhat.com> <20150522232327.GA23114@morn.localdomain> In-Reply-To: <20150522232327.GA23114@morn.localdomain> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] Announcing qboot, a minimal x86 firmware for QEMU List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin O'Connor Cc: qemu-devel , KVM list On 23/05/2015 01:23, Kevin O'Connor wrote: > Hi Paolo, > > I'm curious if you've tried profiling SeaBIOS to see where it is > spending unnecessary time? No, I really wanted to get the absolute minimum time needed to get to the kernel. I announced it publicly because I think it's also instructive. > I wonder if a stripped down SeaBIOS could > obtain sufficient performance. It most likely could. However, some of the features (e.g. booting vmlinuz from parallel flash or, in the future, from persistent memory) probably do not fit SeaBIOS very well. One would have to redo them otherwise, for example using a DMA interface in fw_cfg. Paolo > The page at http://seabios.org/Debugging#Timing_debug_messages > describes how to do basic profiling via timing of debug messages. > > The default SeaBIOS build takes ~180ms on my (old AMD) system. But, > by removing drivers and options via Kconfig I was able to bring it > down to ~25ms. I suspect some additional Kconfig settings and a few > optimizations would make it possible to significantly reduce this > time. > > Cheers, > -Kevin > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >