[illumos-Developer] initial review: bombproof taskq dispatch

[Albert Lee]

On Thu, Jun 30, 2011 at 1:36 PM, Albert Lee <trisk at opensolaris.org> wrote:
> On Wed, May 4, 2011 at 8:11 PM, Garrett D'Amore <garrett at nexenta.com> wrote:
>> On Wed, 2011-05-04 at 18:52 -0500, Jason King wrote:
>>
>>>
>>>
>>>
>>> With the preface that a number of these questions are also partially
>>> for my own edification, so these might be more than a bit ignorant :)
>>>
>>>
>>> This change would seem to ignore any limits on the number of threads
>>> for a taskq (or rather it appears you could create more static
>>> taskq_ent_t's than the limit for the taskq & dispatch all of them).
>>> A lot of the logic within taskq_dispatch seems to depend on this limit
>>> (and in fact the taskq itself allocates max_nthreads # of kthread_t
>>> structures).  Is this correct?
>>
>> Nothing I've done touches the threading stuff... the only thing is that
>> my stuff is totally incompatible with dynamic taskqs.  Folks using
>> dynamic taskqs don't want this prealloc behavior anyway, because dynamic
>> taskq dispatch might actually create whole threads. :-)
>>
>
> We have an effectively unlimited queue length here, given that we
> ignore taskq_{min,max}alloc. Those values are specified at
> taskq_create separately from the thread count, though.
>
> -Albert
>

Gordon pointed out in the Nexenta review that flags = TQ_SLEEP should
still remain for zio so as not to change the #ifndef _KERNEL
behaviour. Sorry to derail your RTI.

-Albert