Re: [uml-devel] [PATCH] host context switch reduction

[Laurent Vivier <LaurentVivier@wanadoo.fr>]

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In include/linux/ptrace.h ,

change

#define PTRACE_SCEMU            25

by

#define PTRACE_SCEMU            31


Le mer 19/05/2004 à 21:39, roland a écrit :
> >OK, as I didn't find skas patch for 2.6 I thought it didn't exist...
> there exists one at:
> http://www.user-mode-linux.org/~blaisorblade/patches/host-skas3-2.6.6-v1.patch
> 
> i applied your patch after applying the skas patch.
> it applies cleanly - good ,
> but compile fails very early with the following errormessage:
> 
> arch/i386/kernel/ptrace.c: In function `sys_ptrace':
> arch/i386/kernel/ptrace.c:509: error: duplicate case value
> arch/i386/kernel/ptrace.c:509: error: previously used here
> make[1]: *** [arch/i386/kernel/ptrace.o] Error 1
> make: *** [arch/i386/kernel] Error 2
> 
> unfortunately, i don`t get this managed to fix myself.
> could you (or someone else) take a look ?
> 
> regards
> roland
> 
> 
> ----- Original Message ----- 
> From: "Laurent Vivier" <LaurentVivier@wanadoo.fr>
> To: "roland" <for_spam@gmx.de>
> Cc: "Jeff Dike" <jdike@addtoit.com>; <user-mode-linux-devel@lists.sourceforge.net>
> Sent: Wednesday, May 19, 2004 8:17 PM
> Subject: Re: [uml-devel] [PATCH] host context switch reduction
> 
> 
> Le mer 19/05/2004 à 20:01, roland a écrit :
> > Hi Laurent !
> > Great!
> > Thanks a lot for your work :)
> >
> > but i have a question:
> >
> > old mail from jeff:
> > >The patches below are from Laurent Vivier who didn't make them public.  They
> > >add a new feature to ptrace on the host which cuts down on the number of
> > >context switches needed for a UML system call, plus makes UML use it
> >
> > so - if your patch adds a new feature for ptrace on the HOST - shouldn`t we need TWO patches for 2.6 ?
> > One patch for uml and one patch for the host ?
> >
> > this one seems for uml only.
> > some of us already run uml 2.6(.x) on a 2.6.(.x) host and put their focus on the "new kernel" (me too).
> 
> OK, as I didn't find skas patch for 2.6 I thought it didn't exist...
> anyway I tried to port the 2.4 host sysemu patch to 2.6, find it
> attached. I never tested it, or compiled it ! I have no system with 2.6
> kernel, and the only I386 system I have is very, very, very noisy...
> it's a good system only when it is switched off ;-) !
> 
> > regards
> > roland
> >
> > ps:
> > since this would be the 2nd patch for the HOST (besides skas), would it make sense, to merge "skas" and "sysemu" into one common
> > HOST-patch (if it has been tested and approved stable) ?
> >
> 
> YES, I think... but Jeff is the boss ;-)
> 
> >
> >
> > ----- Original Message ----- 
> > From: "Laurent Vivier" <LaurentVivier@wanadoo.fr>
> > To: "Jeff Dike" <jdike@addtoit.com>
> > Cc: "roland" <for_spam@gmx.de>; <user-mode-linux-devel@lists.sourceforge.net>
> > Sent: Wednesday, May 19, 2004 7:27 PM
> > Subject: Re: [uml-devel] [PATCH] host context switch reduction
> >
> >
> > Hi,
> >
> > as it is a plebiscite ;-), find attached the patch for UML 2.6.6 and
> > measurements I made on my poor netserver.
> >
> > Laurent
> >
> > Le mar 18/05/2004 à 19:59, Jeff Dike a écrit :
> > > On Tue, May 18, 2004 at 12:22:45AM +0200, roland wrote:
> > > > the question is:
> > > > is the "real world" performance benefit, uml get`s from this patch worth taking your time and is it implemented in a way, so
> > that
> > > > uml maintainers are happy with that ?
> > >
> > > The patch seems reasonable to me.  I'd be happiest with Laurent pushing this
> > > into mainline himself.
> > >
> > > > i cannot really estimate, what performance benefits your patch brings to uml in detail, but what i have seen so far, this
> seems
> > > > quite worth doing the work.  reducing context switches by 1/3 is a LOT, imho - and reducing the execution time of the
> > getpid-loop to
> > > > nearly the half is quite impressive.
> > >
> > > Yeah, but no real workloads do while(1) getpid();
> > >
> > > The kernel build improvement is obviously smaller, but still worth having.
> > >
> > > > are there any "con`s" that argue for that work _NOT_ being done ?
> > >
> > > No.  But testing, and happy reports to the appropriate mailing lists would
> > > help.
> > >
> > > Jeff
> >
> >
> >
> > --------------------------------------------------------------------------------
> >
> >
> > > HP Netserver LH Pro bi-pro 200 MHz / 256 MB RAM
> > >
> > > NATIF:
> > >
> > > netserver:/usr/src# uname -a
> > > Linux netserver 2.4.24-sysemu #4 SMP Tue Feb 17 16:43:11 CET 2004 i686 GNU/Linux
> > >
> > > netserver:/usr/src# time ./getpid 1000000
> > >
> > > real    0m1.763s
> > > user    0m0.910s
> > > sys     0m0.860s
> > >
> > > real    0m1.759s
> > > user    0m0.900s
> > > sys     0m0.870s
> > >
> > > real    0m1.759s
> > > user    0m0.950s
> > > sys     0m0.800s
> > >
> > > UML with sysemu:
> > >
> > > (none):~# uname -a
> > > Linux (none) 2.6.6-1um #10 Wed May 19 12:54:37 CEST 2004 i686 unknown
> > >
> > > (none):/mnt/usr/src# time ./getpid 1000000
> > >
> > > real    1m1.508s
> > > user    0m7.960s
> > > sys     0m53.450s
> > >
> > > real    1m1.881s
> > > user    0m6.630s
> > > sys     0m55.240s
> > >
> > > real    1m1.920s
> > > user    0m6.580s
> > > sys     0m55.340s
> > >
> > > UML w/o sysemu
> > >
> > > real    1m32.833s
> > > user    0m7.610s
> > > sys     1m25.130s
> > >
> > > real    1m32.921s
> > > user    0m7.890s
> > > sys     1m24.980s
> > >
> > > real    1m33.493s
> > > user    0m8.010s
> > > sys     1m24.960s
> > >
> >
> 

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