CODEWITHSUNDEEP
clinuxmultitasking
Helder AC
Helder AC

Reputation: 376

How to optimize two threads running heavy loops

I have more of a conceptual question. Assume one program running two threads. Both threads are running loops all the time. One thread is responsible for streaming data and the other thread is responsible for receiving the file that the first thread has to stream. So the file transfer thread is loops to receive the data which it writes to a file and the streaming thread reads that data from that file as it needs it and streams it.

The problem I see here is how to avoid starvation when the file transfer is taking too much CPU cycles for it's own and thus making the streaming thread lag?

How would I be able to share the CPU effectively between those two threads knowing that the streamer streams data far slower than the file transfer receives it.

I thank you for your advice.

Upvotes: 2

Views: 265

Answers (2)

SKi
SKi

Reputation: 8476

Quite often this kind of problems are solved by using somekind of flow control:

Block the sender when the receiver is busy.

This cause also problems: If your program must be able to fast forward (seek forward), then this is not good idea.

In your case, you could block the file transfer thread when there is more than 2MB unstreamed data in the file. And resume it when there is less than 1MB unstreamed data.

Upvotes: 2

Pavan Manjunath
Pavan Manjunath

Reputation: 28545

See if pthread_setschedparam() helps you balance out the threads' usage of the CPU

From man page of pthread_setschedparam, you can change the thread priorities.

   pthread_setschedparam(pthread_t thread, int policy,
                         const struct sched_param *param);

       struct sched_param {
           int sched_priority;     /* Scheduling priority */
       };

   As can be seen, only one scheduling parameter is supported.  For details of
   the permitted ranges for scheduling priorities in each scheduling policy, see
   sched_setscheduler(2).

Also,

the file transfer is taking too much CPU cycles for it's own

If you read this SO post, it seems to suggest that changing thread priorities may not help. Because the reason the file transfer thread is consuming more CPU cycles is that it needs it. But in your case, you are OK if the file transfering is slowed down as the streamer thread cannot compete anyways! Hence I suggested you to change priorities and deprive file transfer thread of some cycles even if needs it

Upvotes: 0

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