Date: Tue, 24 Feb 2004 14:28:43 -0500 (EST) From: Robert Watson <rwatson@FreeBSD.ORG> To: Willem Jan Withagen <wjw@withagen.nl> Cc: current@FreeBSD.ORG Subject: Re: The effects of WITNESS and INVARIANTS Message-ID: <Pine.NEB.3.96L.1040224142713.55432Z-100000@fledge.watson.org> In-Reply-To: <079d01c3fb06$0e2299b0$471b3dd4@dual>
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On Tue, 24 Feb 2004, Willem Jan Withagen wrote: > Just out of curriousity, and 'cause I've got some idle boxes, I started > to do some (NFS-)performance testing. There is still a long way to go, > but I've but a first obvious result online running on the local server > disk. > > It makes the claims of the effects of WITNESS and INVARIANTS very > obvious. Look especially at the graph for "Sequential block read". > > You might want to have a look at: > http://withagen.dyndns.org/FreeBSD/nfs-performance/index.html. Note > that no NFS data is included. I have some Bonnie-NFS data, but need to > write accompanying test and conclusions for it. > > Suggestions are more than welcomed. My primary suggestion is "Turn off WITNESS and INVARIANTS when benchmarking or for production systems". We turn them off in releases, and once 5.x becomes 5-stable, we'll turn it off by default also. However, they're invaluable tools when debugging the development system, so we have them on in the development branch by default. I would encourage people to generally run with them turned on unless performance of a system requires them to be off, as it really helps the debugging process, as well as helping to identify locking problems as the system evolves. Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Senior Research Scientist, McAfee Research
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