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Date: Tue, 25 Sep 2012 22:02:55 +0200
From: Miroslav Lachman <000.fbsd@quip.cz>
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To: Pawel Jakub Dawidek <pjd@FreeBSD.org>
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Cc: freebsd-fs@FreeBSD.org, Glen Barber <gjb@FreeBSD.org>,
	freebsd-current@FreeBSD.org
Subject: Re: ZFS TRIM support committed to HEAD.
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Pawel Jakub Dawidek wrote:
> On Sun, Sep 23, 2012 at 08:20:41PM -0400, Glen Barber wrote:
>> Hi Pawel,

[...]

>> Great!  Thanks for this.
>>
>> Any chance you can document the following sysctls?
>
> None od the kstat sysctls are documented, they emulate kstat framework
> from Solaris. We would need to modify a lot of vendor code to document
> those in 'sysctl -d' output. It still would be good to have them
> documented even elsewhere, eventhough most are rather self-explanatory.

There were some "sysctl documentation" project on the net (maybe som 
GSoC, I am not sure). Most sysctl's are self-explanatory - unfortunately 
only for knowledgeable developers or authors of the code.
And sometimes even a short description (sysctl -d) is not enough. It 
explains meaning of some counter, but not the condition where / by what 
this counter is triggered.

I think some public page on FreeBSD Wiki bould be good starting place 
for documenting all useful sysctls, their meaning, tips for tuning, what 
one can gain or lose by changing them etc.

>> root@kaos:/root # sysctl -d kstat.zfs.misc.zio_trim
>> kstat.zfs.misc.zio_trim:
>> kstat.zfs.misc.zio_trim.zio_trim_bytes:
>> kstat.zfs.misc.zio_trim.zio_trim_success:
>> kstat.zfs.misc.zio_trim.zio_trim_unsupported:
>> kstat.zfs.misc.zio_trim.zio_trim_failed:

Miroslav Lachman