On Thursday 18 January 2007 14:19, Flavio wrote: > Hello, > > I recently downloaded vanilla kernel sources from www.kernel.org. > I compiled the sources on my host system to do a performance test, > also using "time". > > My CPU is an Intel centrino core duo at 2Ghz. I.e. a SMP processor obviously, right?
> To compile my vanilla testing kernel I did: > > make defconfig > time make -j3 > > Results: > > real: 1m54,535s > user: 3m16,800s > sys: 0m18,920s > > Very good... ;) > > I started UML and i did the same thing.. compiling a vanilla kernel > with the same config file.. > > uml # make defconfig > uml # time make -j3 > > These are the results!!!! > > real 8m45.393s > user 2m53.770s > sys 0m30.310s > > O_O > > It's simply incredible!!!! Why performances decrease in this way???? UML does not support SMP, so it can use just one processor. This is the major slowdown case in your comparison. Compare make -j2 on the host and on the guest: there will still be some slowdown, but not such an high one. Possibly on the guest make -j1 could be better (it would be interesting). Also, the user time is less on UML. The fact that total time is higher is probably due to running with -j3 on a uniprocessor machine, and the fact that the user time is less is probably due to using gcc 3.3 rather than 4 (I seem to recall gcc 4 is slower in compilation than gcc 3). > UML is in skas3 mode. > Command line is "linux ubd0=rootfs.debian ubd1=swapfs.debian > eth0=tuntap,,,192.168.1.110 mem=1000M" > > Please, tell me what can I do... That time is to high!!! -- Inform me of my mistakes, so I can add them to my list! Paolo Giarrusso, aka Blaisorblade http://www.user-mode-linux.org/~blaisorblade Chiacchiera con i tuoi amici in tempo reale! http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ User-mode-linux-user mailing list User-mode-linux-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user
