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Date:      Wed, 8 Apr 2009 18:46:48 +0100 (BST)
From:      Robert Watson <rwatson@FreeBSD.org>
To:        Maxim Konovalov <maxim@macomnet.ru>
Cc:        src-committers@FreeBSD.ORG, svn-src-stable@FreeBSD.ORG, svn-src-all@FreeBSD.ORG, Stephen McKay <mckay@FreeBSD.ORG>, Attilio Rao <attilio@FreeBSD.ORG>, svn-src-stable-7@FreeBSD.ORG
Subject:   Re: svn commit: r190837 - in stable/7/sys: . contrib/pf dev/ath/ath_hal dev/cxgb kern
Message-ID:  <alpine.BSF.2.00.0904081841460.61921@fledge.watson.org>
In-Reply-To: <20090408205159.X1212@mp2.macomnet.net>
References:  <200904080430.n384UGWw043589@svn.freebsd.org> <alpine.BSF.2.00.0904081500220.61921@fledge.watson.org> <3bbf2fe10904080724i381c36fdpb1699def955fdb6d@mail.gmail.com> <alpine.BSF.2.00.0904081527460.61921@fledge.watson.org> <alpine.BSF.2.00.0904081542360.61921@fledge.watson.org> <20090408205159.X1212@mp2.macomnet.net>

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On Wed, 8 Apr 2009, Maxim Konovalov wrote:

>>> While the probes I've added could be used to do this very easily, that's 
>>> not the thrust of the work I'm currently doing.  A useful starting point 
>>> for someone interested in this problem would be a dtrace script like the 
>>> following:
>>>
>>> vfs:namecache:enter:done
>>
>> Also useful: the same script, but using "vfs:namecache:lookup:hit".
>>
> Perhaps we should start to put such scripts somewhere to src/tools.

This sort of script isn't really worth putting in a library, as it's composed 
only of the most basic language constructs and a single probe.  I'd rather 
reserve a tools tree for things that reflect a significant investment in time 
to write, rather than things that can be written in thirty seconds given a 
rudimentary knowledge of the D scripting language.  Otherwise we'll be buried 
in scripts that have little utility and unable to find scripts that are 
useful.

Something we do need to do is begin to formally document the sets of probes 
we're adding, because these sorts of trivial scripts become a lot more obvious 
it you know the probes exist and what they do :-).  I'm not sure what the 
conventions for said man pages should be - perhaps vfs_probes(4) or 
vfs_dtrace(4) or the like, broken into a parts that include a summary of the 
goal of the provider, a list of the specific probes, etc?

Robert N M Watson
Computer Laboratory
University of Cambridge



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