> On Tue, Mar 2, 2010 at 3:20 AM, Henrik Johansen
> <fi...@hotmail.com> wrote:
> > Hi folks,
> >
> > While playing around with the FBT provider I came
> across something I simply can't figure out how to do.
> >
> > I would really like to track I/O to some of our
> zvols - for writes something like this does the trick
> :
> >
> > dtrace -qn 'fbt:zfs:zvol_log_write:entry {
> @[args[0]->zv_name] = count(); }';
> >
> > For reads this proves more difficult since the
> zvol_state struct (which holds the zvol name) is not
> passed as an argument.
> >
> > I haven't used C since school (more than a decade
> ago) so excuse me for mistaking but
> > judging from the zvol_read function in
> http://src.opensolaris.org/source/xref/onnv/onnv-gate/
> usr/src/uts/common/fs/zfs/zvol.c uses a pointer to
> the zvol_state struct instead.
> >
> > How can I get my hands on that data from dtrace ?
>
> zvol_read() gets the pointer to the zvol_state struct
> by caling
> ddi_get_soft_state(). You can get this pointer by
> tracing
> ddi_get_soft_state() predicated on being called from
> inside
> zvol_read().
>
> For example, you could do something like this:
>
> fbt::zvol:read:entry
> {
> self->trace = 1;
> bt::ddi_get_soft_state:return
> / self->trace /
> {
> self->zv = args[1];
> bt::zvol_read:return
> / self->zv /
> {
> @[self->zv->zv_name] = count();
> self->zv = 0;
> self->trace = 0;
>
> Chad
Thanks Chad.
Here is what I ended up with :
fbt::zvol_read:entry
{
self->trace = 1;
}
fbt::ddi_get_soft_state:return
/ self->trace /
{
self->zv = (zvol_state_t *)args[1];
}
fbt::zvol_read:return
/ self->zv /
{
@[self->zv->zv_name] = count();
self->zv = 0;
self->trace = 0;
But this return what appears to be a hexdump as well as the zvol names and
their read counts
[....]
370: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
390: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
3a0: 00 f0 6a 5d 11 ff ff ff 00 d0 ef 62 11 ff ff ff ..j].......b....
[...]
2
tank/intern01_lun_02 3
I can figure out where that comes from ...
/HenrikJ
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