[gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[Mark Knecht]

Hi,
   I'm very unclear about this idea. I've built my new AMD64 machine
using the Gentoo 64-bit setup. The kernel I emerge uses the ~amd64 to
I think I get a full 64-bit kernel. (Please excuse me on this issue.
I'm a bit of a "follow instructions, not necessarily understand the
whole thing" kind of guy on this one, and I definitely feel like I
don't get what's up with 64-bit operation so far...) As far as I know
everything on my machine is supposed to run in 64-bit mode, as far as
I know.

   Anyway, this machine is an AMD64 using a NForce4 motherboard. At
this point, running a kernel with the processor being an AMD64
processor, I'm unable to run the machine with no xruns using Jack. Any
disk activity seems to be the main cause of xruns on this machine.
I've tried the AMD64 64-bit Gentoo kernel as well as ck-sources.
Neither has worked well at all for me. I continue to get xruns and
haven't been able to figure out how to configure the machine to work
well. Bummer.

   Since I've had great results on all of my older 32-bit machines in
the past using gentoo-sources with no modifications I'd like to try
running that on this machine to see if the xruns are a platform issue,
such as the chipset, etc.) or whether they are cuased by operating in
64-bit mode. However, I am completely unable to figure out for myself
if I can run a 32-bit kernel when everything else - glibc, xrog-x11,
qt, gnome, apps, etc., have been compiled as 64-bit capable. Is this
allowed, or will the machine not work running a 32-bit kernel at this
point?

   Sorry if this question sounds brain dead but I'm not a CS/IT
person. I'm a hardware guy and in my world 64-bit is real different
than 32-bit. If I build a kernel for a Athlon will it work with all
the existing libraries that work with 64-bit?

Thanks in advance,
Mark

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Re: [gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[John Myers]

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On Sunday 25 September 2005 19:45, Mark Knecht wrote:
> However, I am completely unable to figure out for myself
> if I can run a 32-bit kernel when everything else - glibc, xrog-x11,
> qt, gnome, apps, etc., have been compiled as 64-bit capable. 
No. The kernel would boot, but it would panic when it tried to run init.

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Re: [gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[Mark Knecht]

On 9/25/05, John Myers <electronerd@monolith3d.com> wrote:
> On Sunday 25 September 2005 19:45, Mark Knecht wrote:
> > However, I am completely unable to figure out for myself
> > if I can run a 32-bit kernel when everything else - glibc, xrog-x11,
> > qt, gnome, apps, etc., have been compiled as 64-bit capable.
> No. The kernel would boot, but it would panic when it tried to run init.
>

Thanks John,
   That's exactly what I was concerned about.

   So, to check how this hardware platform works in a 32-bit mode I
guess I need to do a complete second install on a separate part of the
hard drive as an Athlon. That's a big job that I'm not anxious to do.

Cheers,
Mark

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Re: [gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[Conway S. Smith]

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Mark Knecht wrote:
> On 9/25/05, John Myers <electronerd@monolith3d.com> wrote:
> 
>>On Sunday 25 September 2005 19:45, Mark Knecht wrote:
>>
>>>However, I am completely unable to figure out for myself
>>>if I can run a 32-bit kernel when everything else - glibc, xrog-x11,
>>>qt, gnome, apps, etc., have been compiled as 64-bit capable.
>>
>>No. The kernel would boot, but it would panic when it tried to run init.
>>
> 
> 
> Thanks John,
>    That's exactly what I was concerned about.
> 
>    So, to check how this hardware platform works in a 32-bit mode I
> guess I need to do a complete second install on a separate part of the
> hard drive as an Athlon. That's a big job that I'm not anxious to do.
> 
> Cheers,
> Mark
> 

Depending on what you want to do, you might not have to install both a
64 & 32 bit version of the kernel, when you compile the kernel for amd64
processors it has the kernel option CONFIG_IA32_EMULATION, which will
allow you to run 32 bit applications while running the 64 bit kernel.
If you want even closer to a full 32 bit environment, you can setup a 32
bit chroot.  The only thing you would really need to do a complete
second install (kernel & everything) is if you actually want to test a
32 bit version of the kernel itself.

You might be interested in Gentoo's amd64 technotes' chapter on 32 bit
compatibility:
http://www.gentoo.org/proj/en/base/amd64/technotes/index.xml?part=1&chap=4


Conway S. Smith
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Re: [gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[Matt Randolph]

Mark Knecht wrote:

>   So, to check how this hardware platform works in a 32-bit mode I
>guess I need to do a complete second install on a separate part of the
>hard drive as an Athlon. That's a big job that I'm not anxious to do.
>
>Cheers,
>Mark
>
>  
>

If you're just trying to compare the performance of your software 
between 32-bit and 64-bit kernels, you might try a distro that installs 
more quickly.  If I recall, you can install a complete 32-bit Debian 
system in about half an hour using a Knoppix CD.  Google `knoppix 
"install to hard disk"` for the howto.  I believe you can also get a 
64-bit Debian system just as quickly for comparison by following the 
same procedure but using a Kanotix-64 CD instead.  (You might just 
compare against your existing 64-bit Gentoo system instead, but I don't 
know how fair a fight would be between a hand-tuned Gentoo system and 
one running a binary distro.)

The only hitch I can think of is that some of your applications might 
not be available as Debian binaries in both 32 and 64-bit versions.  
Also, naturally, you won't have the ability to test your software with 
the optimizations afforded by the USE flags you intend to use back here 
in Gentoo-land.  If you would be building your software from source 
anyway, then this would not be an issue.

That being said, I think this experiment would actually be pretty 
academic for most users.  Unless your software is, say, a very CPU 
intensive scientific or multimedia application that was expertly ported 
to 64-bit, it is my understanding that you're probably not going to see 
a performance difference worth writing home about.  I would encourage 
anyone to comment if they know better as I would be delighted to learn 
it was otherwise.

- Matt

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Re: [gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[Mark Knecht]

On 9/26/05, Matt Randolph <mattr@erols.com> wrote:
> Mark Knecht wrote:
>
> >   So, to check how this hardware platform works in a 32-bit mode I
> >guess I need to do a complete second install on a separate part of the
> >hard drive as an Athlon. That's a big job that I'm not anxious to do.
> >
> >Cheers,
> >Mark
> >
> >
> >
>
> If you're just trying to compare the performance of your software
> between 32-bit and 64-bit kernels, you might try a distro that installs
> more quickly.  If I recall, you can install a complete 32-bit Debian
> system in about half an hour using a Knoppix CD.  Google `knoppix
> "install to hard disk"` for the howto.  I believe you can also get a
> 64-bit Debian system just as quickly for comparison by following the
> same procedure but using a Kanotix-64 CD instead.  (You might just
> compare against your existing 64-bit Gentoo system instead, but I don't
> know how fair a fight would be between a hand-tuned Gentoo system and
> one running a binary distro.)
>
> The only hitch I can think of is that some of your applications might
> not be available as Debian binaries in both 32 and 64-bit versions.
> Also, naturally, you won't have the ability to test your software with
> the optimizations afforded by the USE flags you intend to use back here
> in Gentoo-land.  If you would be building your software from source
> anyway, then this would not be an issue.
>
> That being said, I think this experiment would actually be pretty
> academic for most users.  Unless your software is, say, a very CPU
> intensive scientific or multimedia application that was expertly ported
> to 64-bit, it is my understanding that you're probably not going to see
> a performance difference worth writing home about.  I would encourage
> anyone to comment if they know better as I would be delighted to learn
> it was otherwise.
>
> - Matt
>
> --
> gentoo-amd64@gentoo.org mailing list
>
>
Hi Matt,
   As I stated in the first email:

"Any disk activity seems to be the main cause of xruns on this machine."

   If I get xruns (a failure mode of Jack-Audio-Connection-Kit running
on this hardware) then the machine is useless doing the sort of Linux
audio work I want to do so this is the problem I'm trying to solve.
That's my only goal.

   In my case I want to run Gentoo so I'm suspect of comparing any
compiled distro with the results I'm getting on Gentoo's 64-bit
kernel. I don't know what patches they've applied, etc., so I wouldn't
know how to compare that.

   While it is a bunch of work, it might just be best to do a standard
stage 3 Gentoo install on another section of the drive. This way I
have a better comparison, and if it works as well as my other machines
then at least I have a working platform until I can figure out what's
causing the problem in the 64-bit environment.

   Thanks for your inputs.

Cheers,
Mark

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Re: [gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[Volker Armin Hemmann]

On Monday 26 September 2005 16:59, Mark Knecht wrote:

> "Any disk activity seems to be the main cause of xruns on this machine."
>
>    If I get xruns (a failure mode of Jack-Audio-Connection-Kit running
> on this hardware) then the machine is useless doing the sort of Linux
> audio work I want to do so this is the problem I'm trying to solve.
> That's my only goal.

have you checked that 'unmaskirq' is set for your harddisk?

hdparm /dev/hda should look like this:
hdparm /dev/hda

/dev/hda:
 multcount    = 16 (on)
 IO_support   =  1 (32-bit)
 unmaskirq    =  1 (on)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 16383/255/63, sectors = 234493056, start = 0

not this:
hdparm /dev/hda

/dev/hda:
 multcount    =  0 (off)
 IO_support   =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 16383/255/63, sectors = 234493056, start = 0
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Re: [gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[Mark Knecht]

On 9/26/05, Volker Armin Hemmann <volker.armin.hemmann@tu-clausthal.de> wrote:
> On Monday 26 September 2005 16:59, Mark Knecht wrote:
>
> > "Any disk activity seems to be the main cause of xruns on this machine."
> >
> >    If I get xruns (a failure mode of Jack-Audio-Connection-Kit running
> > on this hardware) then the machine is useless doing the sort of Linux
> > audio work I want to do so this is the problem I'm trying to solve.
> > That's my only goal.
>
> have you checked that 'unmaskirq' is set for your harddisk?
>
> hdparm /dev/hda should look like this:
> hdparm /dev/hda
>
> /dev/hda:
>  multcount    = 16 (on)
>  IO_support   =  1 (32-bit)
>  unmaskirq    =  1 (on)
>  using_dma    =  1 (on)
>  keepsettings =  0 (off)
>  readonly     =  0 (off)
>  readahead    = 256 (on)
>  geometry     = 16383/255/63, sectors = 234493056, start = 0
>
> not this:
> hdparm /dev/hda
>
> /dev/hda:
>  multcount    =  0 (off)
>  IO_support   =  0 (default 16-bit)
>  unmaskirq    =  0 (off)
>  using_dma    =  1 (on)
>  keepsettings =  0 (off)
>  readonly     =  0 (off)
>  readahead    = 256 (on)
>  geometry     = 16383/255/63, sectors = 234493056, start = 0

Only problem is these are SATA drives and they don't tell me much
compared to EIDE drives when using hdparm. Also their error messages
running hdparm are a bit of a concern, although typical from what I've
read.

lightning ~ # hdparm /dev/sda

/dev/sda:
 IO_support   =  0 (default 16-bit)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 30401/255/63, sectors = 250059350016, start = 0
lightning ~ #
lightning ~ # hdparm -tT /dev/sda

/dev/sda:
 Timing cached reads:   2040 MB in  2.00 seconds = 1018.12 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate
ioctl for device
 Timing buffered disk reads:  198 MB in  3.02 seconds =  65.62 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate
ioctl for device
lightning ~ #

Thanks,
Mark

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Re: [gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[Daniel Gryniewicz]

On Mon, 2005-09-26 at 08:45 -0700, Mark Knecht wrote:
> Only problem is these are SATA drives and they don't tell me much
> compared to EIDE drives when using hdparm. Also their error messages
> running hdparm are a bit of a concern, although typical from what I've
> read.
> 
> lightning ~ # hdparm /dev/sda
> 
> /dev/sda:
>  IO_support   =  0 (default 16-bit)
>  readonly     =  0 (off)
>  readahead    = 256 (on)
>  geometry     = 30401/255/63, sectors = 250059350016, start = 0
> lightning ~ #
> lightning ~ # hdparm -tT /dev/sda
> 
> /dev/sda:
>  Timing cached reads:   2040 MB in  2.00 seconds = 1018.12 MB/sec
> HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate
> ioctl for device
>  Timing buffered disk reads:  198 MB in  3.02 seconds =  65.62 MB/sec
> HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate
> ioctl for device
> lightning ~ #
> 

You might try sdparm.  It doesn't give very much output on my SATA
drive, but it's supposed to give more on others.

Daniel

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Re: [gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[Mark Knecht]

On 9/26/05, Daniel Gryniewicz <dang@gentoo.org> wrote:
>
> You might try sdparm.  It doesn't give very much output on my SATA
> drive, but it's supposed to give more on others.
>
> Daniel

I hadn't heard of this one. Thanks.

It actually gives lots of output on my system. Use the --all option.
However none of the info is very descriptive of helpful to me as of
yet.

Cheers,
Mark

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Re: [gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[John C. Shimek]

You do a straight 32bit install on your amd64.  The amd64 is 32bit 
capable.  I don't know whether to call your precessor an athlon or maybe 
a generic x86 processor.  It is the same as running Windows 2000/XP on 
this processor.  The OS thinks it has a 32bit CPU. Only you are limited 
to 32bit limitation on hardware, mainly memory and possibly harddrive, I 
don't know. 

Also, have you only tried the ~amd64 kernels?  Stick with the non "~" 
software for a stable/production machine unless you absulutely need a 
newer version in that is marked "~".  The "~" before the amd64 or x86 or 
any other platform means this version has not been completely tested and 
thus is unstable.  Many times, it is stable just needs to be verified.  
Other times, especially when dealing with hardware or assembly 
programming or sloppy programming, it isn't stable.  If you are running 
~amd64, I would suggest backing off to the stable amd64 and rebuild with 
that.  It will give you slightly older version but more tested 
versions.  I am sure others can point in the correct direction for 
rebuild your system if needed, let more experieced wiser minds help 
where they can.

Good Luck and let us know how it goes one way or the other,
JCS

Mark Knecht wrote:

>Hi,
>   I'm very unclear about this idea. I've built my new AMD64 machine
>using the Gentoo 64-bit setup. The kernel I emerge uses the ~amd64 to
>I think I get a full 64-bit kernel. (Please excuse me on this issue.
>I'm a bit of a "follow instructions, not necessarily understand the
>whole thing" kind of guy on this one, and I definitely feel like I
>don't get what's up with 64-bit operation so far...) As far as I know
>everything on my machine is supposed to run in 64-bit mode, as far as
>I know.
>
>   Anyway, this machine is an AMD64 using a NForce4 motherboard. At
>this point, running a kernel with the processor being an AMD64
>processor, I'm unable to run the machine with no xruns using Jack. Any
>disk activity seems to be the main cause of xruns on this machine.
>I've tried the AMD64 64-bit Gentoo kernel as well as ck-sources.
>Neither has worked well at all for me. I continue to get xruns and
>haven't been able to figure out how to configure the machine to work
>well. Bummer.
>
>   Since I've had great results on all of my older 32-bit machines in
>the past using gentoo-sources with no modifications I'd like to try
>running that on this machine to see if the xruns are a platform issue,
>such as the chipset, etc.) or whether they are cuased by operating in
>64-bit mode. However, I am completely unable to figure out for myself
>if I can run a 32-bit kernel when everything else - glibc, xrog-x11,
>qt, gnome, apps, etc., have been compiled as 64-bit capable. Is this
>allowed, or will the machine not work running a 32-bit kernel at this
>point?
>
>   Sorry if this question sounds brain dead but I'm not a CS/IT
>person. I'm a hardware guy and in my world 64-bit is real different
>than 32-bit. If I build a kernel for a Athlon will it work with all
>the existing libraries that work with 64-bit?
>
>Thanks in advance,
>Mark
>
>  
>

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Re: [gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[John Myers]

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On Sunday 25 September 2005 20:47, John C. Shimek wrote:
> You do a straight 32bit install on your amd64. 
That's beside the point. His question was whether he could just use a 32-bit 
kernel with a 64-bit userland (i.e. not having to recompile everything), the 
answer to which is no.

> I don't know whether to call your precessor an athlon or maybe
> a generic x86 processor.
Depending on his version of GCC, he would use -march=athlon64 or 
-march=athlon-xp, i believe

> It is the same as running Windows 2000/XP on this processor.  The OS thinks 
> it has a 32bit CPU. Only you are limited to 32bit limitation on hardware,
And you miss out on a bunch of extra general-purpose registers, which is 
actually what makes x86_64 faster than x86, not the 64-bitness, which would 
otherwise make it slower due to larger code size

> mainly memory
AFAIK, only if you have >= 4GB

> and possibly harddrive, I don't know. 
No.

> I am sure others can point in the correct direction for 
> rebuild your system if needed, let more experieced wiser minds help
> where they can.
Except that's what he's trying to avoid...

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