Path: utzoo!attcan!uunet!know!zaphod.mps.ohio-state.edu!wuarchive!psuvax1!rutgers!deejay!gear!cadlab!staff
From: staff@cadlab.sublink.ORG (Alex Martelli)
Newsgroups: comp.arch
Subject: Re: IOStone
Message-ID: <291@cadlab.sublink.ORG>
Date: 18 Oct 90 21:26:25 GMT
References: <7834@ucdavis.ucdavis.edu>
Organization: CAD.LAB, Bologna, Italia
Lines: 34

becker@iris.ucdavis.edu (Jeffrey Becker) writes:
	...
>We welcome any CONSTRUCTIVE SUGGESTIONS you might have in designing an
>IO system metric.

I have one, and as a beta-site for IOstone made it (but never got any
feedback about it, nor about all I reported - maybe my mail was flakier
than usual): do NOT place open() and close() in a tight inner loop!!!

Do the system-traces show that io-intensive programs open() and close()
a file each time they need to read()/write() a few hundreds or thousands
bytes from/to it...?  If so, they look suspiciously like NFS-based I/O
to me, rather than 'real' disk I/O!-)

Then again, maybe the final IOstone does NOT have the inner-loop open()
and close(); although I didn't hear anything from you about this point,
surely I wasn't the only one to make it - it's a rather clear one.

I do not have the hard data to back this opinion up, but I believe 
that open() and close() are quite a bit less frequent than read() and
write(), so it woule be quite reasonable to accept some performance 
hit in the former calls if it bought you a somewhat smaller increase
in the latter ones... but such a design would lead to poor IOstone
numbers (in the 'beta' release, which is all I was able to see).

Alex Martelli - CAD.LAB s.p.a., v. Stalingrado 45, Bologna, Italia
Email: (work:) staff@cadlab.sublink.org, (home:) alex@am.sublink.org
Phone: (work:) ++39 (51) 371099, (home:) ++39 (51) 250434; 
Fax: ++39 (51) 366964 (work only; any time of day or night).
-- 
Alex Martelli - CAD.LAB s.p.a., v. Stalingrado 45, Bologna, Italia
Email: (work:) staff@cadlab.sublink.org, (home:) alex@am.sublink.org
Phone: (work:) ++39 (51) 371099, (home:) ++39 (51) 250434; 
Fax: ++39 (51) 366964 (work only; any time of day or night).