[Live-devel] BasicTaskScheduler not reading fast enough?

[Rawling, Stuart]

>The problem with this is that it can potentially lead to 'livelock'
>Situations - e.g., if the handler of a 'delayed task' itself calls
>"TaskScheduler::schedulerDelayedTask()" to set up a new delayed task
>(especially if the 'delay' is zero).  That's why
>"BasicTaskScheduler::SingleStep()" always tries to handle at least
>one socket (and iterates through all the available sockets).

Are you saying that my optimization for handling alarms early could cause an
issue? ( I also call it after
the select as well).
I understand your statement to indicate that if the task that is called in
fDelayQueue.handleAlarm
adds an schedules an additional task, then this would also have to be
handled in the handleAlarm function.
If so, isn¹t this also the case when we call handleAlarm after the select?

Another thing I noticed was that I do not believe the turnOn /
turnOffBackgroundReadHandling
functions are handling the fMaxNumSockets in the most efficient way.  When I
read the man page for
select it says: 
³ nfds is the highest-numbered file descriptor in any of the three sets,
plus 1.³ 
(On windows I believe nfds is ignored).

Looking at the code, the turnOn function seems to be fine, but the turnOff
function just negates
the fMaxNumSockets variable, rather than finding the current highest
numbered file descriptor.

For example, if we added fds: 1, 2, 99 then fMaxNumSockets becomes 100.  If
we then removed 99,
fMaxNumSockets becomes 99, not 3 as I would expect (and select expects
according to the man page).
 I am not sure how select is implemented under the hood, but I am guessing
this might cause an
inefficiency as I suspect it tests all file descriptors between 0 and nfds
­1;

Regards,
Stuart



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