From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: Announcing qboot, a minimal x86 firmware for QEMU Date: Mon, 25 May 2015 14:52:51 +0200 Message-ID: <55631B23.3090303@redhat.com> References: <555DE2EF.1000509@redhat.com> <20150522232327.GA23114@morn.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: qemu-devel , KVM list To: Kevin O'Connor Return-path: Received: from mail-wi0-f177.google.com ([209.85.212.177]:32773 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750781AbbEYMwz (ORCPT ); Mon, 25 May 2015 08:52:55 -0400 Received: by wicmx19 with SMTP id mx19so39862219wic.0 for ; Mon, 25 May 2015 05:52:54 -0700 (PDT) In-Reply-To: <20150522232327.GA23114@morn.localdomain> Sender: kvm-owner@vger.kernel.org List-ID: 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 >