Date: Fri, 22 Sep 2006 08:59:51 +0300 From: Danny Braniss <danny@cs.huji.ac.il> To: freebsd-hackers@FreeBSD.ORG Subject: Re: numbers don't lie ... Message-ID: <E1GQe4l-000OA9-Dq@cs1.cs.huji.ac.il> In-Reply-To: <200609211831.k8LIV57C040532@lurza.secnetix.de> References: <200609211831.k8LIV57C040532@lurza.secnetix.de>
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> Danny Braniss wrote: > > you might have a point, but this started when I asked why, two > > boxes, under similar test gave idential real times, but very different > > user times. > > Right, and the answer was: One box has a much faster CPU, > so it's user time is smaller, but buildworld isn't purely > CPU-bound, and because of I/O delays the real times end > up to be about the same. In other words: The faster box > had to wait more often for the disk than the slower box. > > If both of your machines have enough RAM, it would be > interesting to repeat the test with /usr/src being in a > RAM disk, so read I/O doesn't play that much of a role. > > Best regards > Oliver > > PS: Numbers don't lie ... but are often misinterpreted. or missused by salesmen/politician/etc :-) i have run many tests, even having /usr/src in memory, the results where posted some days ago, but here they are again: make: dell 2950 OS: Freebsd 6.2-PRERELEASE cpu: XEON 3.20GHz dualcore * 2 memory: 4GB src & obj real user system hyper -------------------- --------- ---------- --------- ----- Dell PERC 5/i RAID 0 24m17.73s 1h4m31.49s 15m47.44s no Dell PERC 5/i RAID 0 22m3.39s 1h38m46.84s 28m54.18s yes iSCSI/netapp 26m49.98s 1h4m26.77s 16m12.89s no src obj -------------------- md Dell PERC 5/i 24m7.22s 1h4m44.94s 16m24.45 no so something is still fishy in the state of Denmark. or, in the case of this box, the cpu is so slow, that no matter how fast the I/O is is does not change the equation. I will try to run similar tests on the amd/sun, but have to wait till some real work finishes. danny
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