Date: Tue, 24 Feb 2004 23:10:47 +0100 From: "Willem Jan Withagen" <wjw@withagen.nl> To: "Robert Watson" <rwatson@FreeBSD.ORG> Cc: current@FreeBSD.ORG Subject: Re: The effects of WITNESS and INVARIANTS Message-ID: <084901c3fb23$0ec737f0$471b3dd4@dual> References: <Pine.NEB.3.96L.1040224142713.55432Z-100000@fledge.watson.org>
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From: "Robert Watson" <rwatson@FreeBSD.ORG> > 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. Hi Robert, I understand your concern and will take your remark as made here, and put it in the document as a "Nota Bene"... And I'll emphasise the fact that the 5-stable fact is the turning corner for this matter. --WjW
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