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Date:      Sun, 13 Oct 2013 11:59:27 -0400
From:      George Neville-Neil <gnn@freebsd.org>
To:        Pedro Giffuni <pfg@freebsd.org>
Cc:        dtrace@FreeBSD.org
Subject:   Re: Dtrace providers wanted list
Message-ID:  <9455846D-2301-4055-9AA1-99177F21A3AC@freebsd.org>
In-Reply-To: <6A4B05EA-D9C7-4014-BF86-4676EF01071C@FreeBSD.org>
References:  <52546385.2050203@FreeBSD.org> <20131010042544.GB65451@raichu> <52596B73.2050702@FreeBSD.org> <6A4B05EA-D9C7-4014-BF86-4676EF01071C@FreeBSD.org>

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On Oct 12, 2013, at 22:17 , Pedro Giffuni <pfg@freebsd.org> wrote:

>=20
> Il giorno 12/ott/2013, alle ore 10:32, Pedro Giffuni <pfg@FreeBSD.org> =
ha scritto:
>=20
>> On 09.10.2013 23:25, Mark Johnston wrote:
>>> On Tue, Oct 08, 2013 at 02:56:53PM -0500, Pedro Giffuni wrote:
>>>> Hello;
>>>>=20
>>>> Sometime ago I looked around the list of Oracle's DTrace providers.
>>>>=20
>>>> https://wikis.oracle.com/display/DTrace/Providers
>>>>=20
>>>> We absolutely want them and although extremely useful as it is, =
DTrace
>>>> won't be complete until we have them all ;). For the time being we
>>>> should probably focus on getting the really critical ones though.
>>>>=20
>>>> The first in the list that we don't have that I think is critical =
is
>>>> mentioned in Brendan Gregg's FreeBSD specific blog post:
>>>>=20
>>>> =
http://dtrace.org/blogs/brendan/2013/09/25/the-use-method-freebsd-performa=
nce-checklist/
>>>>=20
>>>> "Tracing paging is tricker until the vminfo provider is added; you =
could
>>>> try tracing from swap_pager_putpages() and swap_pager_getpages(), =
but I
>>>> didn=92t see an easy way to walk back to a thread struct; another =
approach
>>>> may be via vm_fault_hold(). Good luck. ..."
>>=20
>> I started looking at this but it is somewhat more work than expected:
>> Solaris has a specific vminfo interface in sysinfo.h. It looks very =
handy
>> for providing general vm statistics but our vm is different and I am
>> not sure we want to go into implementing such interface. It depends
>> on a VM guru, anyways.
>>=20
>> OTOH, I found the fsinfo provider:
>>=20
>> =
https://bitbucket.org/illumos/illumos-gate/commits/5b50c2dcfdf948c4e4f0b88=
0eb76210067e7af7c
>>=20
>> Our VFS does have some similarity so this may be easier/doable, plus
>> it may be needed by the scsi and ZFS providers.
>=20
> Ugh =85
>=20
> I looked at this one too, and similarly to the vminfo provider, there =
is a vopstats
> structure in vnode.h that we don't have.
>=20
> Both the vopstats and vminfo structures are used to support Solaris' =
kstat(1M) utility.
> In other words, this is an in kernel system made to report statistics. =
While it
> seems natural to use them for DTrace in Solaris, we would have to =
reimplement
> it in some way if we want to have equivalent providers in FreeBSD. :-(
>=20
> I am afraid that the CPC Provider may have similar issues but I =
haven't looked at it.
>=20

The CPC provider can be hooked to hwpmc, but one thing I note in the =
Illumos provider
is that they preface things with PAPI (which is actually its own =
package, though the Illumos
folks seem to have just snagged the name and don't use the actual =
library).

Best,
George



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