Date: Thu, 9 Nov 1995 11:11:21 +1100 From: Bruce Evans <bde@zeta.org.au> To: current@freebsd.org, faulkner@mpd.tandem.com Subject: Re: iozone and mount -o async Message-ID: <199511090011.LAA16890@godzilla.zeta.org.au>
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>Can you test the fs mounted async with iozone? I am getting a slowdown >mounted async! This is normal. Mounting async disables the pessimization of doing async (but ASAP) writes for full buffers. This pessimization is actually an optimization for stupid benchmarks such as iozone. It forces the physical i/o to be done ASAP instead of later when iozone does an fsync(). Most applications don't do fsync()s so their i/o gets done when the system thinks best. It might be useful to have an fadvise() syscall (like madvise() but working :-). Applications that do large sequential i/o's could use it to suggest write-through. Bruce
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