[uml-devel] uml on iA-64

[uml-devel] uml on iA-64

[pierre.gentile]

Hello all,

Has anyone tried to implement user-mode-linux (skas patch and um
architecture) on an Itanium IA-64 machine ?

                    ////
                   (o o)
===============oOO==(_)==OOo=============
  Pierre Gentile



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Re: [uml-devel] uml on iA-64

[Jeff Dike]

pierre.gentile@mpsa.com said:
> Has anyone tried to implement user-mode-linux (skas patch and um
> architecture) on an Itanium IA-64 machine ? 

Not really.  I have an IA64 box sitting next to me, and starting a port to
it is on my list once I acquire some free time.

				Jeff



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Re: [uml-devel] uml on iA-64

[Matt Zimmerman]

On Sat, Oct 25, 2003 at 01:03:22PM -0400, Jeff Dike wrote:

> pierre.gentile@mpsa.com said:
> > Has anyone tried to implement user-mode-linux (skas patch and um
> > architecture) on an Itanium IA-64 machine ? 
> 
> Not really.  I have an IA64 box sitting next to me, and starting a port to
> it is on my list once I acquire some free time.

I did some preliminary investigation into making ia64 UML-friendly as a host
(the changing syscall numbers bit), and after discovering why it won't work,
I sent pleas for help to some HP folks to find out if it would be easy to
fix.  I did get one interested response, but no reply to my followup as yet.

-- 
 - mdz


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[uml-devel] Problem with Real-Time Scheduling

[Michael Ralston]

I've come across a problem with running a user-mode-linux instance with
RR-Scheduling. When I attempt to start a server with chrt the host
system panics. I can start a uml in normal (other) scheduling, and then
change it to RR-Scheduling and it works fine, until I try to stop the
uml... then I get the same kernel panic.

I'm using the skas-3 patch on a 2.4.21 kernel, and 2.4.21-6um. If you
need the specific output of the kernel panic, I can get it...

Just as a related question... how would different scheduling the
different 'threads' of the UML effect performance? As far as I know..
the first 'linux' process actually does all the work and the extra
processes are for the different IO the UML does, eg network, block
devices etc? Would increasing the priority of the IO over the priority
of the main process have an effect on network performance for example?

Michael Ralston




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Re: [uml-devel] Problem with Real-Time Scheduling

[Jeff Dike]

ralston@stral.net said:
> I've come across a problem with running a user-mode-linux instance
> with RR-Scheduling. When I attempt to start a server with chrt the
> host system panics. I can start a uml in normal (other) scheduling,
> and then change it to RR-Scheduling and it works fine, until I try to
> stop the uml... then I get the same kernel panic.

Any time the host panics, it's time to send the details to LKML.

> how would different scheduling the different 'threads' of the UML
> effect performance? As far as I know.. the first 'linux' process
> actually does all the work and the extra processes are for the
> different IO the UML does, eg network, block devices etc? Would
> increasing the priority of the IO over the priority of the main
> process have an effect on network performance for example?

In skas mode, the first process runs the kernel, the second runs processes, 
and the other two handle SIGIO emulation and SIGWINCHes.  So, those two don't
matter, and first two are never running at the same time, so their relative
priorities don't matter.

				Jeff



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Re: [uml-devel] Problem with Real-Time Scheduling

[Nuno Silva]

Hi!

Jeff Dike wrote:

[..]

> In skas mode, the first process runs the kernel, the second runs processes, 
> and the other two handle SIGIO emulation and SIGWINCHes.  So, those two don't
> matter, and first two are never running at the same time, so their relative
> priorities don't matter.
> 
> 				Jeff
> 

Wouldn't it be nice if the threads updated their argv[0] to something like
"argv[0]-kernel"
"argv[0]-userspace"
"argv[0]-sigio"
"argv[0]-sigwinch"?

I would send a patch but my first attempt didn't work... Can this be 
done? Maybe renicing the threads could help in environments where you 
have lots of UMLs running? Like having the kernel runnig at -10 and 
userspace at 19 and sigio at 19? Maybe this could make the "time" inside 
UML more consistent in high loads?

Comments?

Regards,
Nuno Silva



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Re: [uml-devel] Problem with Real-Time Scheduling

[BlaisorBlade]

Alle 22:23, domenica 26 ottobre 2003, Nuno Silva ha scritto:
> Hi!
>
> Wouldn't it be nice if the threads updated their argv[0] to something like
> "argv[0]-kernel"
> "argv[0]-userspace"
> "argv[0]-sigio"
> "argv[0]-sigwinch"?
>
> I would send a patch but my first attempt didn't work... Can this be
> done?
> Maybe renicing the threads could help in environments where you
> have lots of UMLs running? Like having the kernel runnig at -10 and
> userspace at 19 and sigio at 19?
Avoid nice=19 since there have been some notable patches in 2.5(even present 
in 2.4-ck tree) to make such task run only in place of the idle task. And 
having the kernel running at -10 means having high permissions.
Adding an option to make UML switch to some UID after startup is not 
difficult. But first we need to know until which point it needs root 
priviledges. And probably, capabilities are just enough. And at some point, 
in 2.6 there will be setcapability extended attributes(it's not hard now that 
extended attrs work).
> Maybe this could make the "time" inside
> UML more consistent in high loads?
>
> Comments?
>
> Regards,
> Nuno Silva
-- 
cat <<EOSIGN
Paolo Giarrusso, aka Blaisorblade
Linux Kernel 2.4.21/2.6.0-test on an i686; Linux registered user n. 292729
EOSIGN



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Re: [uml-devel] Problem with Real-Time Scheduling

[Nuno Silva]

Hello!

BlaisorBlade wrote:
> Alle 22:23, domenica 26 ottobre 2003, Nuno Silva ha scritto:
> 
>>Hi!
>>
>>Wouldn't it be nice if the threads updated their argv[0] to something like
>>"argv[0]-kernel"
>>"argv[0]-userspace"
>>"argv[0]-sigio"
>>"argv[0]-sigwinch"?
>>
>>I would send a patch but my first attempt didn't work... Can this be
>>done?
>>Maybe renicing the threads could help in environments where you
>>have lots of UMLs running? Like having the kernel runnig at -10 and
>>userspace at 19 and sigio at 19?
> 
> Avoid nice=19 since there have been some notable patches in 2.5(even present 
> in 2.4-ck tree) to make such task run only in place of the idle task. And 
> having the kernel running at -10 means having high permissions.
> Adding an option to make UML switch to some UID after startup is not 
> difficult. But first we need to know until which point it needs root 


I wasn't talking about running UML as root. Just an easy way to identify 
each thread.

After a script (maybe run by root, maybe not) can easily spot which 
thread does what we could renice the process, remove linux capabilities, 
killall -STOP linux-sigio, etc... ;)


> priviledges. And probably, capabilities are just enough. And at some point, 
> in 2.6 there will be setcapability extended attributes(it's not hard now that 
> extended attrs work).
> 
>>Maybe this could make the "time" inside
>>UML more consistent in high loads?
>>

This would be really good! :)

Regards,
Nuno Silva



>>Comments?
>>
>>Regards,
>>Nuno Silva



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RE: [uml-devel] uml on iA-64

[Wichmann, Mats D]

> > pierre.gentile@mpsa.com said:
> > > Has anyone tried to implement user-mode-linux (skas patch and um
> > > architecture) on an Itanium IA-64 machine ? 
> > 
> > Not really.  I have an IA64 box sitting next to me, and 
> > starting a port to it is on my list once I acquire some free time.
> 
> I did some preliminary investigation into making ia64 
> UML-friendly as a host (the changing syscall numbers bit), 
> and after discovering why it won't work, I sent pleas for 
> help to some HP folks to find out if it would be easy to
> fix.  I did get one interested response, but no reply to my 
> followup as yet.

It would be good if we'd be able to collect information
like this somewhere.  I know there was a porting effort
at one of the Gelato member institutions (UIUC, I think),
that released a preliminary patch earlier this year, but
it's been silent on that front since.

A collection of experiences would be a useful resource,
I'd think.



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Re: [uml-devel] uml on iA-64

[Jeff Dike]

mats.d.wichmann@intel.com said:
> It would be good if we'd be able to collect information like this
> somewhere.

It'd be good if someone would just do it.  It's not that hard, and will be
a lot easier once I get the Opteron port merged.

A patch will be way more useful than a collection of experiences.

				Jeff



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RE: [uml-devel] uml on iA-64

[Wichmann, Mats D]

> mats.d.wichmann@intel.com said:
> > It would be good if we'd be able to collect information like this
> > somewhere.
> 
> It'd be good if someone would just do it.  It's not that 
> hard, and will be a lot easier once I get the Opteron port merged.
> 
> A patch will be way more useful than a collection of experiences.

Well, sure... but it would be nice if someone new
starting on such a project could benefit from knowing
of past pitfalls, right?  Given that there have been
one or more efforts that didn't bear fruit, maybe
it's harder than it looks (except for Jeff who might
actually know what he's doing :-).

If I had the time-and-skills I'd have been working on
this long ago but the former has been so lacking I
haven't even gotten to test the latter :-(



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