Date: Wed, 20 Sep 2006 18:04:31 +0300 From: Danny Braniss <danny@cs.huji.ac.il> To: Kris Kennaway <kris@obsecurity.org> Cc: freebsd-hackers@freebsd.org, Dmitry Morozovsky <marck@rinet.ru> Subject: Re: numbers don't lie ... Message-ID: <E1GQ3cl-000O7T-90@cs1.cs.huji.ac.il> In-Reply-To: <20060919173421.GA45928@xor.obsecurity.org> References: <200609141232.k8ECWTXj045191@lurza.secnetix.de> <20060919160511.T33371@woozle.rinet.ru> <20060919173421.GA45928@xor.obsecurity.org>
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> > --FCuugMFkClbJLl1L > Content-Type: text/plain; charset=us-ascii > Content-Disposition: inline > Content-Transfer-Encoding: quoted-printable > > On Tue, Sep 19, 2006 at 04:11:12PM +0400, Dmitry Morozovsky wrote: > > On Thu, 14 Sep 2006, Oliver Fromme wrote: > >=20 > > OF> Because buildworld is I/O-bound on systems with sufficiently > > OF> fast processors. > > OF>=20 > > OF> Try putting the contents of /usr/src into a RAM disk and > > OF> repeat the benchmark. The numbers might look a little > > OF> different then. Of course, you should have sufficient RAM > > OF> in the machines -- If they're going to swap to the disks, > > OF> your benchmark won't be happy. > > OF>=20 > > OF> I think putting /usr/obj onto a RAM disk is _not_ necessary > > OF> because of soft-updates, so the processes shouldn't block > > OF> on writes. > >=20 > > My experiments show that if you have enough memory to host radmdrive for= > =20 > > /usr/src you'd better leave it for caching - there were no statistically > > meaningful performance difference, at least on machines with 1G+ RAM. > > Really? My measurements show the opposite (on a system with 16GB of > RAM). > > Kris here are a bunch of new numbers: make: dell 2950 OS: Freebsd 6.2-PRERELEASE cpu: XEON 3.20GHz dualcore * 2 memory: 4GB no swap configured/used. make buildworld -j 8: 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, if numbers are to be believed: 1- hypert helps in the real time, but user and system are bigger. allot of sweat for a very small gain. 2- src in memory made no change. 3- slow disc (iscsi) vs. very fast disk (PERC 5/i RAID 0) - about 1:3 speed, produced less than 10% gain in time. danny
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