Date: Wed, 20 Sep 2006 14:50:08 +0200 (CEST) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-hackers@FreeBSD.ORG Subject: Re: numbers don't lie ... Message-ID: <200609201250.k8KCo8sm048910@lurza.secnetix.de> In-Reply-To: <20060919160511.T33371@woozle.rinet.ru>
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Dmitry Morozovsky wrote: > Oliver Fromme wrote: > > 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. > > My experiments show that if you have enough memory to host radmdrive for > /usr/src you'd better leave it for caching - there were no statistically > meaningful performance difference, at least on machines with 1G+ RAM. That might only be true if you have enough RAM to keep _all_ buildworld files (src, obj, toolchain) in the cache _and_ you pre-read all of /usr/src before actually starting the buildworld, so it is in the cache. If you don't have that much RAM, but enough to store /usr/src, then using a RAM disk for it is a win. Reading /usr/src from a physical disk certainly requires quite some I/O that takes more than zero time. 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. "File names are infinite in length, where infinity is set to 255 characters." -- Peter Collinson, "The Unix File System"
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