Date: Thu, 14 Sep 2006 14:32:29 +0200 (CEST) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-hackers@FreeBSD.ORG, danny@cs.huji.ac.il Subject: Re: numbers don't lie ... Message-ID: <200609141232.k8ECWTXj045191@lurza.secnetix.de> In-Reply-To: <E1GNoDy-0004CF-5k@cs1.cs.huji.ac.il>
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Danny Braniss wrote: > [...] > but the original question stands: > why is the user time between the boxes so different, Because the dual-core Opteron is significantly faster than the (single-core) Xeon, so buildworld takes less (user) CPU time. By the way, certain parts of buildworld make use of both cores, even if you don't use the -j option. If CFLAGS contains the -pipe option (which is the default), various stages of the toolchain can run in parallel (preprocessor, compiler, assembler). > whyle the real time remains the same? Because buildworld is I/O-bound on systems with sufficiently fast processors. Try putting the contents of /usr/src into a RAM disk and repeat the benchmark. The numbers might look a little different then. Of course, you should have sufficient RAM in the machines -- If they're going to swap to the disks, your benchmark won't be happy. I think putting /usr/obj onto a RAM disk is _not_ necessary because of soft-updates, so the processes shouldn't block on writes. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd Any opinions expressed in this message may be personal to the author and may not necessarily reflect the opinions of secnetix in any way. "C is quirky, flawed, and an enormous success." -- Dennis M. Ritchie.
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