[dtrace-discuss] self-> in BEGIN probe

[Robert Milkowski]

Hello dtrace-discuss,


With a bug id

6495013 Loops and recursion in metaslab_ff_alloc can kill
        performance, even on a pool with lots of free data

There's associated D script below.

What's the point setting self->in_metaslab in a BEGIN probe?
I'm not talking about setting it to 0 as this is not necessary but
rather about self-> variables in BEGIN probe. I guess it has no
rather about self-> predictable meaning, right?


#!/usr/sbin/dtrace -s

#pragma D option quiet

BEGIN
{
         self->in_metaslab = 0;
}
fbt::metaslab_ff_alloc:entry
/self->in_metaslab == 0/
{
         self->in_metaslab = 1;
         self->loopcount = 0;
}
fbt::avl_walk:entry
/self->in_metaslab/
{
         self->loopcount++;
}
fbt::metaslab_ff_alloc:return
/self->in_metaslab/
{
         self->in_metaslab = 0;
         @loops["Loops count"] = quantize(self->loopcount);
         self->loopcount = 0;
}

-- 
Best regards,
 Robert                          mailto:rmilkowski at task.gda.pl
                                     http://milek.blogspot.com