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Date:      Sun, 5 Apr 1998 22:03:36 -0500 (EST)
From:      "John S. Dyson" <toor@dyson.iquest.net>
To:        thomma@slip.net (Tamiji Homma)
Cc:        freebsd-current@FreeBSD.ORG
Subject:   Re: disk performance difference
Message-ID:  <199804060303.WAA07645@dyson.iquest.net>
In-Reply-To: <E0yM1zh-0006HN-00@slip-3> from Tamiji Homma at "Apr 5, 98 07:50:44 pm"

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> Hi,
> 
> I am not a -current but SNAP CD user.  I noticed something interesting,
> that 19971006-SNAP disk performance is much greater than 19980222-SNAP
> specially on my SCSI disk according to what Bonnie's says.  In fact,
> SCSI disk performance is very poor...
>
Try building a -current kernel, and I wonder if you see such a regression
now.  There have been several improvements (and fixes) lately.

(It is fairly easy to build a -current kernel, running on a recent snapshot.
 Sometimes, you'll have to rebuild libkvm and ps, but shouldn't be a major
 problem, once you go through the learning curve.)

> 
> 19980222-SNAP:     3315.51 real      2313.34 user       599.32 sys
> 19971006-SNAP:     3370.48 real      2328.91 user       633.53 sys
> 
> The 'make buildworld' is done under following conditions:
>     /usr/src on wd0
>     /usr/obj on ccd0 (/dev/sd0c /dev/sd1c)
>     NOPROFILE, NOCLEAN, NOTCL, -pipe, async,noatime
> 
> I don't see much difference (actually faster on newer SNAP, which is
> good:) between two SNAPs when I do make buildworld.
> 
> Can anybody elaborate why? 
>
I don't have any details, but there have been numerous problems introduced
in the name of improvements.  It is likely that you are running a snap with
the ioopt feature enabled, and that option was not well thought out before
including in the tree.  (I know, I implemented it.)

John

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