From owner-freebsd-arch@FreeBSD.ORG  Tue Jun 14 11:44:08 2005
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To: Sue Howard <howardsue@gmail.com>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Tue, 14 Jun 2005 19:33:01 +0800."
	<1e89cd510506140433437f7b7@mail.gmail.com> 
Date: Tue, 14 Jun 2005 13:44:02 +0200
Message-ID: <36765.1118749442@critter.freebsd.dk>
Sender: phk@critter.freebsd.dk
Cc: arch@freebsd.org, ken@freebsd.org
Subject: Re: [DCR] Remove devstat 
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In message <1e89cd510506140433437f7b7@mail.gmail.com>, Sue Howard writes:
>Hi,
>
>I found devstat is not widely used in the device drivers. Based the
>grep result of 'devstat_new_entry', it shows only cam, ata, fd,
>geom_disk are using it. In my workstation, the output of 'sysctl
>kern.devstat' shows:

>I am wondering if devstat can be replaced by the sysctl nodes %desc,
>%pnpinfo etc that jhb introduced. Almost all the information devstat
>can provide can be also exposed by such sysctl node.

Uhm, are we confused here ?

Devstat is what is used for collecting transaction statistics for
disks and scsi general devices in general.

Programs like iostat and gstat uses it.

The old access path (iostat) uses sysctls, but the new and practically
overhead free access path is mmap(2) which gstat uses.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.