On Oct 30, 2008, at 9:25 AM, Cyril Plisko wrote:
> On Thu, Oct 30, 2008 at 6:01 PM, Sumit Gupta <[EMAIL PROTECTED]>
> wrote:
>> Hi Cyril
>>
>> The LU entry points are called using kernel threads (called worker
>> threads
>> inside the framework). The thread pool is dynamically grown from 4
>> to 256 (a
>> soft limit) by stmf based on the load. The task spread is round
>> robin among
>> all the workers. Regarding sleeping, the framework is designed to
>> allow for
>> both synchronous and asynchronous operations. You can choose a
>> model which
>> is best for your application. As a guideline, if you have to sleep
>> for
>> several milliseconds, you should not block the worker thread and
>> use the
>> lu_poll entry point (by calling stmf_task_poll_lu()). But if your
>> sleep is
>> just to implement synchronous operations and your backend is
>> reasonably
>> fast, its ok to block the worker.
>
>
> Sumit,
>
> thanks for explanation. As for the duration of the sleep - I was
> wondering about calling kmem_alloc() with KM_SLEEP vs KM_NOSLEEP
> inside LU entry point. I have no idea how long this will sleep.
It is ok to use KM_SLEEP inside LU entry points as in most cases you
will have memory and the call wont sleep. If you are running out of
memory then your system performance is not going to be good anyway.
Which is what will happen if the worker sleeps for a long time.
> I also didn't quite grok your note on using lu_poll. Can you please
> give some example ?
The framework provides a mechanism for the LU to say "I cannot
handle this task right now, call me back later". The LU does so by
calling stmf_task_poll_lu() and the framework later on calls the
lu_poll entry point. This is useful for very slow tasks like
rewinding a tape or ejecting media etc. This is also documented in
detail in the stmf spec.
Sumit
>
>>
>> Sumit
>>
>> On Oct 29, 2008, at 3:21 PM, Cyril Plisko wrote:
>>
>>> Hello,
>>>
>>> I have another question on COMSTAR:
>>>
>>> where can I find the information about the context of the LU entry
>>> points ? I am trying to figure out when am I allowed to sleep...
>>>
>>> --
>>> Regards,
>>> Cyril
>>> _______________________________________________
>>> storage-discuss mailing list
>>> [email protected]
>>> http://mail.opensolaris.org/mailman/listinfo/storage-discuss
>>
>>
>
>
>
> --
> Regards,
> Cyril
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