Date: Thu, 14 Sep 2006 15:00:38 +0200 From: des@des.no (Dag-Erling =?iso-8859-1?Q?Sm=F8rgrav?=) To: Danny Braniss <danny@cs.huji.ac.il> Cc: freebsd-hackers@freebsd.org Subject: Re: numbers don't lie ... Message-ID: <863bauk3gp.fsf@dwp.des.no> In-Reply-To: <E1GNOLq-000DC2-1Q@cs1.cs.huji.ac.il> (Danny Braniss's message of "Wed, 13 Sep 2006 09:36:01 %2B0300") References: <E1GNOLq-000DC2-1Q@cs1.cs.huji.ac.il>
next in thread | previous in thread | raw e-mail | index | archive | help
Danny Braniss <danny@cs.huji.ac.il> writes: > Im testing these 2 boxes, Sun X4100 and Dell-2950, and: > > SUN X4100: Dual Core AMD Opteron(tm) Processor 280 (2393.19-MHz K8-class= CPU) > one 70g sata disk > DELL 2950: Intel(R) Xeon(TM) CPU 3.20GHz (3192.98-MHz K8-class CPU) > 4 sata disks + raid0 > > they both run identical 6.1-STABLE. > > my 'cpu benchmark' shows the amd being much better than the intel. > but, doing a make buildworld give interesting results: > > dell-2950 : make -j16 TARGET_ARCH=3Damd64 buildworld : 24m17.41s real 1h3= m3.26s user 17m15.07s sys > dell-2950 : make -j8 TARGET_ARCH=3Damd64 buildworld : 24m8.28s real 1h2m5= 9.38s user 16m16.20s sys > > sunfire : make -j16 TARGET_ARCH=3Damd64 buildworld : 24m21.38s real 49m6.= 68s user 14m22.64s sys > sunfire : make -j8 TARGET_ARCH=3Damd64 buildworld : 23m47.69s real 48m53.= 58s user 13m44.81s sys > > which probably says something about my 'cpu benchmark' :-( > but why is the user time so much different between the boxes? I don't see what's so surprising. User time reflects time actually spent compiling stuff; you can see there that the Opteron is much faster than the Xeon. Sys time is time spent executing kernel code on behalf of the build, which is mostly time spent processing I/O requests (but does not include time spent actually reading from or writing to disks). The reason why there is no significant difference in wall time between the two is that buildworld is mostly bound by I/O and memory bandwidth, not by CPU power. If you have enough memory, place /usr/src and /usr/obj on malloc()-backed RAM disks and see if it makes any difference. DES --=20 Dag-Erling Sm=F8rgrav - des@des.no
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?863bauk3gp.fsf>