Dtrace providers wanted list

[Pedro Giffuni]

Il giorno 12/ott/2013, alle ore 10:32, Pedro Giffuni <pfg at FreeBSD.org> ha scritto:

> On 09.10.2013 23:25, Mark Johnston wrote:
>> On Tue, Oct 08, 2013 at 02:56:53PM -0500, Pedro Giffuni wrote:
>>> Hello;
>>> 
>>> Sometime ago I looked around the list of Oracle's DTrace providers.
>>> 
>>> https://wikis.oracle.com/display/DTrace/Providers
>>> 
>>> 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.
>>> 
>>> 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:
>>> 
>>> http://dtrace.org/blogs/brendan/2013/09/25/the-use-method-freebsd-performance-checklist/
>>> 
>>> "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’t see an easy way to walk back to a thread struct; another approach
>>> may be via vm_fault_hold(). Good luck. ..."
> 
> 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.
> 
> OTOH, I found the fsinfo provider:
> 
> https://bitbucket.org/illumos/illumos-gate/commits/5b50c2dcfdf948c4e4f0b880eb76210067e7af7c
> 
> Our VFS does have some similarity so this may be easier/doable, plus
> it may be needed by the scsi and ZFS providers.

Ugh …

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.

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. :-(

I am afraid that the CPC Provider may have similar issues but I haven't looked at it.

Pedro.