Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r266826, r266827
Move some duplicated hook definitions from machine-dependent files to
kern_dtrace.c.

MFC r257417: Remove references to an unused fasttrap probe hook

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Initial commit of an I/O provider for DTrace on FreeBSD.

These probes are most useful when looking into the structures
they provide, which are listed in io.d. For example:

dtrace -n 'io:genunix::start { printf("%d\n", args[0]->bio_bcount); }'

Note that the I/O systems in FreeBSD and Solaris/Illumos are sufficiently
different that there is not a 1:1 mapping from scripts that work
with one to the other.
MFC after: 1 month

Add DTrace support to the new NFS client. This is essentially
cloned from the old NFS client, plus additions for NFSv4. A
review of this code is in progress, however it was felt by the
reviewer that it could go in now, before code slush. Any changes
required by the review can be committed as bug fixes later.

better integrate cyclic module with clocksource/eventtimer subsystem

Now in the case when one-shot timers are used cyclic events should fire
closer to theier scheduled times. As the cyclic is currently used only
to drive DTrace profile provider, this is the area where the change
makes a difference.

Reviewed by: mav (earlier version, a while ago)
X-MFC after: clocksource/eventtimer subsystem

Add the necessary DTrace function pointers.

Sponsored by: The FreeBSD Foundation

Rename the cyclic global variable lapic_cyclic_clock_func to just
cyclic_clock_func. This will make more sense when we start developing non
x86 cyclic version.

Add DTrace probes to the NFS access and attribute caches. Access cache
events are:

nfsclient:accesscache:flush:done
nfsclient:accesscache:get:hit
nfsclient:accesscache:get:miss
nfsclient:accesscache:load:done

They pass the vnode, uid, and requested or loaded access mode (if any);
the load event may also report a load error if the RPC fails.

The attribute cache events are:

nfsclient:attrcache:flush:done
nfsclient:attrcache:get:hit
nfsclient:attrcache:get:miss
nfsclient:attrcache:load:done

They pass the vnode, optionally the vattr if one is present (hit or load),
and in the case of a load event, also a possible RPC error.

MFC after: 1 month
Sponsored by: Google, Inc.

Add dtnfsclient, a first cut at an NFSv2/v3 client reuest DTrace
provider. The NFS client exposes 'start' and 'done' probes for NFSv2
and NFSv3 RPCs when using the new RPC implementation, passing in the
vnode, mbuf chain, credential, and NFSv2 or NFSv3 procedure number.
For 'done' probes, the error number is also available.

Probes are named in the following way:

...
nfsclient:nfs2:write:start
nfsclient:nfs2:write:done
...
nfsclient:nfs3:access:start
nfsclient:nfs3:access:done
...

Access to the unmarshalled arguments is not easily available at this
point in the stack, but the passed probe arguments are sufficient to
to a lot of interesting things in practice. Technically, these probes
may cover multiple RPC retransmits, and even transactions if the
transaction ID change as a result of authentication failure or a
jukebox error from the server, but usefully capture the intent of a
single NFS request, such as access, getattr, write, etc.

Typical use might involve profiling RPC latency by system call, number
of RPCs, how often a getattr leads to a call to access, when failed
access control checks occur, etc. More detailed RPC information might
best be provided by adding a krpc provider. It would also be useful
to add NFS client probes for events such as the access cache or
attribute cache satisfying requests without an RPC.

Sponsored by: Google, Inc.
MFC after: 1 month

Add the DTrace shim layer definitions.

All shim hooks are defined here. This is the interface between BSD
code in FreeBSD and CDDL code from OpenSolaris.

The hooks defined here are pre-processed out from the source files
when the KDTRACE_HOOKS kernel option isn't defined.