Date: Fri, 22 Dec 2006 12:29:11 +1300 From: Mark Kirkwood <markir@paradise.net.nz> To: freebsd-stable@FreeBSD.ORG, markir@paradise.net.nz Subject: Re: Cached file read performance with 6.2-PRERELEASE Message-ID: <458B18C7.6010406@paradise.net.nz> In-Reply-To: <200612211353.kBLDrG1M085224@lurza.secnetix.de> References: <200612211353.kBLDrG1M085224@lurza.secnetix.de>
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Oliver Fromme wrote: > Mark Kirkwood wrote: > > Exactly, that's why I did the comparison - I think you missed the part > > where I mentioned the 2 systems were *identical* with respect to cpus, > > memory, mobo - in fact even the power supplies are identical too! > > So I assume your benchmark measured the performance of the > zero and null devices under FreeBSD and Linux. > No - that was peripheral to the benchmark, and I should not have sent that message 'cause actually I've taken dev/zero and /dev/null *out* of the picture - check earlier messages with the .c prog attached, I'm using read(2) and lseek(2) to access a "real" file, that just happens (i.e. has been arranged) to be cached! > This is a quote from the "cstream" docs: "These special > devices speed varies greatly among operating systems, > redirecting from it isn't appropriate benchmarking and > a waste of resources anyway." > > I suggest you try cstream (ports/misc/cstream) instead of > dd. It supports built-in zero creation and data sink, so > you don't have to use the zero and null devices at all, > eliminating their overhead. It would be interesting how > that will change your benchmark numbers. > Thanks - I was suspicious of these special files, but had no evidence! Cheers Mark
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