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

["roland" <for_spam@gmx.de>]

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).

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) ?



----- 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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