From owner-freebsd-current  Thu Nov  9 11:00:09 1995
Return-Path: owner-current
Received: (from root@localhost)
          by freefall.freebsd.org (8.6.12/8.6.6) id LAA01356
          for current-outgoing; Thu, 9 Nov 1995 11:00:09 -0800
Received: from devnull.mpd.tandem.com ([131.124.4.29])
          by freefall.freebsd.org (8.6.12/8.6.6) with ESMTP id LAA01341
          for <current@freebsd.org>; Thu, 9 Nov 1995 11:00:05 -0800
Received: from olympus by devnull.mpd.tandem.com (8.6.8/8.6.6)
	id MAA04032; Thu, 9 Nov 1995 12:58:42 -0600
Received: by olympus (4.1/TSS2.1)
	id AA27364; Thu, 9 Nov 95 12:58:51 CST
From: faulkner@mpd.tandem.com (Boyd Faulkner)
Message-Id: <9511091858.AA27364@olympus>
Subject: Re: iozone and mount -o async
To: bde@zeta.org.au (Bruce Evans)
Date: Thu, 9 Nov 1995 12:58:50 -0600 (CST)
Cc: current@freebsd.org, faulkner@devnull
In-Reply-To: <199511090011.LAA16890@godzilla.zeta.org.au> from "Bruce Evans" at Nov 9, 95 11:11:21 am
X-Mailer: ELM [version 2.4 PL17]
Content-Type: text
Content-Length: 1115      
Sender: owner-current@freebsd.org
Precedence: bulk

> 
> >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
> 

So how can I test my performance?  iozone is no good.  dd is no better.
cp and cat file1 > file2 don't do as well either.  It is because I 
am doing these things to a big file vs. a lot of smaller files?

Thanks again,
Boyd
-- 
_______________________________________________________________________

 Boyd Faulkner - faulkner@isd.tandem.com - http://cactus.org/~faulkner
_______________________________________________________________________