Actually, I thought that there might be some kind of race condition
like that, but that really can't be it. See the time stamps?
Speculation 5 was set 9 seconds earlier, and speculation 6 was set 1.6
seconds earlier. The point is that I am seeing a very small number
of syspoll calls and they tend to wait a relatively long time. I could
see getting that kind of race once in awhile at that rate, or even all
of the time if the rate of pollsys calls was very high, but that isn't
the case. Also, there is the one process that I know is waiting in
syspoll that doesn't show up here at all.
Pramod Batni wrote:
>
>
>
>>
>> 1 2 :END 5 9163
>> ===================================================
>>
>>
>> 1 2 :END 6 1686
>> ===================================================
>>
>>
>>
>> See the problem? In this case speculations 5 and 6 both have non-zero
>> ts array entries (or they would not have printed) but there is
>> nothing in the speculation buffer (otherwise there would have been the
>> first set of traces printed). Any ideas why this is happening?
>>
> Consider the following 2 probes firing on 2 different cpu's at
> approximately the same time.
>> } \
>> END \
>> /ts[this->spec]/ \
>> { \
>> commit(this->spec); \
>> this->spec++; \
>> }
>>
>>
>>
>> syscall::pollsys:return
>> /self->spec/
>> {
>> ts[self->spec] = 0;
>> discard(self->spec);
>> self->spec = 0;
>> }
>>
>>
> The interleaved execution of the predicate and the clause could lead to
> the kind of output you are observing.
> The first probe would find ts[this->spec] to be non-zero and before it
> can execute 'commit(this->spec)' the second
> probe would fire and execute 'discard(self->spec)' . The contents of the
> speculative buffer are discarded and the 'commit(this->spec)'
> would become a nop.
> Such a sequence could explain the missing data for speculation 5 and 6.
>
>
> Pramod
--
blu
There are two rules in life:
Rule 1- Don't tell people everything you know
----------------------------------------------------------------------
Brian Utterback - Solaris RPE, Sun Microsystems, Inc.
Ph:877-259-7345, Em:brian.utterback-at-ess-you-enn-dot-kom
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