From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.12] helo=sc8-sf-mx2.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1BQbpS-0007Va-5p for user-mode-linux-devel@lists.sourceforge.net; Wed, 19 May 2004 17:54:34 -0700 Received: from mail.gmx.de ([213.165.64.20] helo=mail.gmx.net) by sc8-sf-mx2.sourceforge.net with smtp (Exim 4.30) id 1BQbpQ-0007tb-HK for user-mode-linux-devel@lists.sourceforge.net; Wed, 19 May 2004 17:54:32 -0700 Message-ID: <04f101c43e05$ffcdea20$2000000a@schlepptopp> From: "roland" References: <20040229043549.GA8583@ccure.user-mode-linux.org> <02dc01c43c4a$bb7c0490$2000000a@schlepptopp> <1084831251.1230.4.camel@chartreuse> <03ff01c43c5d$7db6e5e0$2000000a@schlepptopp> <20040518175904.GB29114@ccure.user-mode-linux.org> <1084987654.2250.4.camel@chartreuse> <012201c43dcb$402ca6a0$2000000a@schlepptopp> <1084990661.2255.28.camel@chartreuse> Subject: Re: [uml-devel] [PATCH] host context switch reduction MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Thu, 20 May 2004 03:01:34 +0200 Content-Transfer-Encoding: quoted-printable To: Laurent Vivier Cc: Jeff Dike , user-mode-linux-devel@lists.sourceforge.net while testing laurents patch, i have made the following interesting observation: if i run a getpid-loop inside one uml, the other uml`s behaviour becomes quite sluggish - this doesn`t seem to have a relation to laurents patch - i just recognized this for the first time, because i never did getpid-loops inside a uml. :) ok - i would say: yes - the system is heavily stressed - a busy uml makes the other one behave sluggish, too .....but..... why don`t i see any sluggish behaviour on the HOST itself ? want to reproduce? compile this little program and transfer it to your uml-root_fs`s -------------------------- int main(void) { int i; for(i=3D0;i<1000000;i++) getpid(); } -------------------------- - let it run in one uml and the other uml(s) get sluggish - typing into the= window and issuing commands gives very slow response - on the HOST there is no noticeable performance loss - typing,echoing, ls = -la, df -kl, ... all seems normal and "feels" quite good. - stop the getpid program and start another cpu/io hog (e.g. "while true;do= find /;done) inside one uml and compare that behaviour. other uml`s behave quite ok - = the host, too. no sluggish behaviour. maybe this behaviour is quite normal (ok - a getpid-loop is a worst case sc= enario) - but my system knowledge isn`t good enough, to explain , what`s going on here in= detail. is it, because the processing overhead of an uml is so high - so typing a c= har or issuing a command "costs" so much more in an uml, so that we just can "see" the perfo= rmance drop here, and not on the host ? regards roland ----- Original Message -----=20 From: "Laurent Vivier" To: "roland" Cc: "Jeff Dike" ; Sent: Wednesday, May 19, 2004 8:17 PM Subject: Re: [uml-devel] [PATCH] host context switch reduction Le mer 19/05/2004 =E0 20:01, roland a =E9crit : > 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 m= ake 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 -----=20 > From: "Laurent Vivier" > To: "Jeff Dike" > Cc: "roland" ; > 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 =E0 19:59, Jeff Dike a =E9crit : > > 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 wo= rth 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 LO= T, 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 havi= ng. > > > > > are there any "con`s" that argue for that work _NOT_ being done ? > > > > No. But testing, and happy reports to the appropriate mailing lists wo= uld > > 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 > > > ------------------------------------------------------- This SF.Net email is sponsored by: Oracle 10g Get certified on the hottest thing ever to hit the market... Oracle 10g.=20 Take an Oracle 10g class now, and we'll give you the exam FREE. http://ads.osdn.com/?ad_id=3D3149&alloc_id=3D8166&op=3Dclick _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel