From: Kevin O'Connor <kevin@koconnor.net>
To: "Richard W.M. Jones" <rjones@redhat.com>
Cc: marc.mari.barcelo@gmail.com, Paolo Bonzini <pbonzini@redhat.com>,
qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@gmail.com>
Subject: Re: [Qemu-devel] Why is SeaBIOS used with -kernel?
Date: Fri, 1 Apr 2016 11:14:56 -0400 [thread overview]
Message-ID: <20160401151456.GC25490@morn.lan> (raw)
In-Reply-To: <20160401150623.GN32728@redhat.com>
On Fri, Apr 01, 2016 at 04:06:23PM +0100, Richard W.M. Jones wrote:
> On Fri, Apr 01, 2016 at 10:58:19AM -0400, Kevin O'Connor wrote:
> > On Fri, Apr 01, 2016 at 09:44:56AM +0100, Richard W.M. Jones wrote:
> > > On Fri, Apr 01, 2016 at 10:24:37AM +0200, Paolo Bonzini wrote:
> > > > On 01/04/2016 10:14, Richard W.M. Jones wrote:
> > > > > Found it: only CONFIG_MPTABLE=y was necessary. It boots with:
> > > > >
> > > > > # CONFIG_PIRTABLE is not set
> > > > > CONFIG_MPTABLE=y
> > > > > # CONFIG_SMBIOS is not set
> > > > > # CONFIG_ACPI is not set
> > > >
> > > > If you add all three it should not give any slowdown and will provide
> > > > full hardware features to the kernel. qboot does ACPI and PCI bus
> > > > assignment (it doesn't do SMBIOS because I got bored debugging it. :))
> > >
> > > Enabling all 4 adds about 2ms.
> >
> > CONFIG_SMBIOS and CONFIG_ACPI only control the legacy internal bios
> > tables. One would disable CONFIG_FW_ROMFILE_LOAD to disable the newer
> > ACPI tables; there is no config option currently to disable the newer
> > smbios tables.
> >
> > These config names are a bit misleading, so they probably should be
> > changed in seabios.
> >
> > I didn't expect disabling the above options to do anything besides
> > reduce the size of the seabios binary, so I'm a bit suprised it saved
> > 2ms. Did you have something on your qemu command-line to avoid
> > generating acpi/smbios tables?
>
> The standard deviation of that number over 5 runs was 1ms, so I'm
> somewhat confident the 2ms is measuring something real. In the grand
> scheme of things it doesn't matter at all.
>
> I'm not using any qemu command line options related to acpi or smbios.
Okay - interesting.
Considering you have acpi=off in linux, you might want to try timing
with CONFIG_ACPI, CONFIG_SMBIOS, and CONFIG_FW_ROMFILE_LOAD all
disabled. The acpi romfile loading stuff takes 4ms in my tests.
It's not clear to me that disabling acpi is a good plan, but it can't
hurt to time it.
-Kevin
next prev parent reply other threads:[~2016-04-01 15:15 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-19 20:31 [Qemu-devel] Why is SeaBIOS used with -kernel? Richard W.M. Jones
2016-03-21 7:58 ` Gerd Hoffmann
2016-03-21 8:37 ` Richard W.M. Jones
2016-03-21 9:40 ` Gerd Hoffmann
2016-03-31 9:21 ` Stefan Hajnoczi
2016-03-31 16:22 ` Kevin O'Connor
[not found] ` <20160331221039.GA32728@redhat.com>
2016-03-31 22:17 ` Richard W.M. Jones
2016-03-31 22:44 ` Kevin O'Connor
2016-04-01 7:55 ` Richard W.M. Jones
2016-04-01 8:03 ` Paolo Bonzini
2016-04-01 8:47 ` Richard W.M. Jones
2016-04-01 8:51 ` Paolo Bonzini
2016-04-01 8:57 ` Richard W.M. Jones
2016-04-01 9:05 ` Paolo Bonzini
2016-04-01 8:02 ` Richard W.M. Jones
2016-04-01 8:11 ` Paolo Bonzini
2016-04-01 8:14 ` Richard W.M. Jones
2016-04-01 8:24 ` Paolo Bonzini
2016-04-01 8:44 ` Richard W.M. Jones
2016-04-01 8:47 ` Paolo Bonzini
2016-04-01 8:49 ` Vasiliy Tolstov
2016-04-01 9:16 ` Dr. David Alan Gilbert
2016-04-01 9:18 ` Gerd Hoffmann
2016-04-01 10:17 ` Richard W.M. Jones
2016-04-01 11:07 ` Gerd Hoffmann
2016-04-01 11:11 ` Richard W.M. Jones
2016-04-01 11:20 ` Richard W.M. Jones
2016-04-01 11:21 ` Paolo Bonzini
2016-04-01 11:26 ` Richard W.M. Jones
2016-04-05 4:38 ` Kevin Wolf
2016-04-05 8:04 ` Richard W.M. Jones
2016-04-05 8:11 ` Kevin Wolf
2016-04-05 9:19 ` Richard W.M. Jones
2016-04-05 9:26 ` Kevin Wolf
2016-04-01 11:32 ` Gerd Hoffmann
2016-04-01 11:49 ` Richard W.M. Jones
2016-04-01 15:35 ` Kevin O'Connor
2016-04-01 16:03 ` Paolo Bonzini
2016-04-01 18:41 ` Richard W.M. Jones
2016-04-01 18:59 ` Richard W.M. Jones
2016-04-01 19:04 ` Kevin O'Connor
2016-04-01 19:10 ` Richard W.M. Jones
2016-04-01 19:15 ` Richard W.M. Jones
2016-04-01 19:44 ` Kevin O'Connor
2016-04-01 20:25 ` Richard W.M. Jones
2016-04-01 20:05 ` Kevin O'Connor
2016-04-01 20:46 ` Richard W.M. Jones
2016-04-01 22:25 ` Kevin O'Connor
2016-04-02 7:51 ` Richard W.M. Jones
2016-04-02 5:30 ` Paolo Bonzini
2016-04-01 15:08 ` Kevin O'Connor
2016-04-01 14:58 ` Kevin O'Connor
2016-04-01 15:06 ` Richard W.M. Jones
2016-04-01 15:14 ` Kevin O'Connor [this message]
2016-04-01 8:19 ` Richard W.M. Jones
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