Date: Wed, 20 Sep 2006 17:56:04 +0400 (MSD) From: Dmitry Morozovsky <marck@rinet.ru> To: Eric Anderson <anderson@centtech.com> Cc: freebsd-hackers@freebsd.org Subject: Re: numbers don't lie ... Message-ID: <20060920175539.Q63482@woozle.rinet.ru> In-Reply-To: <451140F8.9030500@centtech.com> References: <200609201250.k8KCo8sm048910@lurza.secnetix.de> <451140F8.9030500@centtech.com>
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On Wed, 20 Sep 2006, Eric Anderson wrote: EA> > > > My experiments show that if you have enough memory to host radmdrive EA> > for > /usr/src you'd better leave it for caching - there were no EA> > statistically EA> > > meaningful performance difference, at least on machines with 1G+ RAM. EA> > EA> > That might only be true if you have enough RAM to keep EA> > _all_ buildworld files (src, obj, toolchain) in the cache EA> > _and_ you pre-read all of /usr/src before actually starting EA> > the buildworld, so it is in the cache. If you don't have EA> > that much RAM, but enough to store /usr/src, then using EA> > a RAM disk for it is a win. EA> > EA> > Reading /usr/src from a physical disk certainly requires EA> > quite some I/O that takes more than zero time. EA> EA> But, in order to populate the ram disk, you must read /usr/src also from EA> something, and that also takes time, which you should include in the full EA> scope. ... and that populates cache with src files as well ;-) Sincerely, D.Marck [DM5020, MCK-RIPE, DM3-RIPN] ------------------------------------------------------------------------ *** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck@rinet.ru *** ------------------------------------------------------------------------
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