hi !
I have enhanced laurents sysemu patch a little bit.

the attached patch adds an additional commandline-switch to uml.
if you specify "sysemu" on the commandline, it makes uml use sysemu, if
the host has the sysemu patch,too.
if you don`t specify it, uml doesn`t use sysemu at all.
this makes it easier to compare uml behaviour with and without sysemu (you
don`t need 2 different kernels for that purpose)

Laurent - if you like it, perhaps you could publish that on your website or
include it in your sysemu patch?

regards
roland

ps:
sorry - i have only done it for 2.6.6

pps:
since this is my first patch, maybe this is far from being perfect. feel free
to comment. :)


>Hi,
>
>I put all related information at this URL:
>
>http://perso.wanadoo.fr/laurent.vivier/UML
>
>I have modified the 2.4.24 patches to set PTRACE_SYSEMU to 31 too.
>This modification allows to use 2.4.24 UML on 2.6.6 host, and 2.6.6 UML
>on 2.4.24 host.
>
>Regards,
>Laurent
>
>Le jeu 20/05/2004 à 04:30, roland a écrit :
> Hi Laurent,
> i wondered about:
> "Checking syscall emulation patch for ptrace...missing"
>
> so  - i dig into this:
>
> the uml-patch needs to be adjusted to the fix you gave for the host patch:
> in arch/um/kernel/skas/include/ptrace-skas.h
> i changed :
> #define PTRACE_SYSEMU 25
> to
> #define PTRACE_SYSEMU 31
>
> whoha - now sysemu patch is running with 2.6.6  :)
>
> same positive effect: the getpid loop runs MUCH faster.
> i have tested some other commands and if i run a "vmstat 1" on the HOST,
> i can see the context-swap-rate drop down significantly.
>
> great!
>
> laurent, can you post the sysemu uml and host patch again in ONE mail,
> containing the corrected defines?
> others will probably have it easier this way!
> (maybe some notes about how it works and what it does would be helpful, too)
>
> thanks a lot!
>
> now we need some real-world performance tests/comparisons :)
> regards
> roland
>
> ps:
> i will do some more tests. maybe blaisorblade already wants to mention that
> patch in his 2.6 documentation at: http://www.user-mode-linux.org/~blaisorblade/ ?
>
>
>
>
>
>
> >in include/linux/ptrace.h ,
> >change
> >#define PTRACE_SCEMU            25
> >by
> >#define PTRACE_SCEMU            31
>
>
>
>
>
> ----- Original Message ----- 
> From: "Laurent Vivier" <LaurentVivier@wanadoo.fr>
> To: "roland" <for_spam@gmx.de>
> Cc: <user-mode-linux-devel@lists.sourceforge.net>
> Sent: Wednesday, May 19, 2004 9:49 PM
> Subject: Re: [uml-devel] [PATCH] host context switch reduction
>