> One more thing. On the T1000, I run this script:
>
> #!/usr/sbin/dtrace -s
> profile-997
> /arg1 && execname == "ssh"/
> {
> @[execname,pid,ustack()]=count()
> }
> profile-997
> /arg1 && execname == "sshd"/
> {
> @[execname,pid,ustack()]=count()
> }
> profile-50s
> {
> exit(0);
> }
> END
> {
> trunc(@,1000)
> }
>
> and I get a whole bunch of errors that look like this:
>
> dtrace: error on enabled probe ID 1 (ID 1853: profile:::profile-997):
> invalid address (0x3bb98000) in action #4
>
> The only difference on these is that the address is different each
> time. I don't get these message on the v220 at all. Any ideas what the
> problem is?
>
I had a quick look at this a while ago and here are a few
observations I made. Firstly though, what version of Solaris are
you running? Do you see the errors spasmodically or all the time?
It could be down to the fact that early on in a processes lifecycle
and very periodically during its lifetime (for mmu synchronisation)
we can have an invalid user mmu context. When we go and walk the
user stack we'll have an invalid secondary context and you'll
see these errors.
Also it could be that you're catching a process very early on in
its lifecycle when we have an address space setup but we have no
mappings loaded. When we walk the stack we induce user pagefaults
with the loads and get the invalid address errors.
I would expect to see these errors on all SPARC and not just
4v though so I'm not sure why you don't see these errors on
4u though. Could be something completely different though...
Jon.
>
> Brian Utterback wrote:
>
>> I have been doing some profiling using the profile provider. I have a
>> command that runs more slowly on the T1000 than it does on prior
>> systems and I am trying to find out why. Using the profile provider at
>> 1000 hz, and aggregating on the ustack output, I find that the same
>> function appears at the top of the stack on both platforms, but on
>> each there are specific instruction locations within the function that
>> appear most often and these are different on the two platforms. They
>> are consistent on a platform. That is when I re-run the test on one
>> platform, about 4 specific PC locations will appear in the top spots,
>> but on that platform it is always the same 4 and the 4 are different
>> between the platforms.
>>
>> So, I am trying to figure out whether or not there is something
>> special happening at those locations, or just before or just after, or
>> are they just artifacts of how the profile provider works? There are
>> two function calls with this function, but neither set of 4 locations
>> seem to be near the calls. And if the time was really spent inside the
>> next lower down level, wouldn't that have been reflected in the ustack
>> output?
>>
>
>
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