few more trivial Q's (bear with me I'm a newbie to kernel world):
1) As I said I have a process that spawns 2 threads(thread A and B).I am
trying to measure the exact time @ which they are being scheduled.For this I
am using the rdtsc() (when threads A and B come) in enqueue_task()..where
they are being inserted into the priority array.
Is this a correct way of measuring?
2) also in task_struct.....is "tgid" the id of my process and each of
threads hav a unique pid??
3) I saw frm the kernel docs tht realtime tasks hav priority 0 to 99. So
using setscheduler means do I have to enforce a priority in one of these
ranges to make my threads as soft/hard realtime task.
thanks in advance for your patience.
From: Nick Piggin <[email protected]>
To: Arun Srinivas <[email protected]>
CC: [email protected]
Subject: Re: help needed pls. scheduler(kernel 2.6) + hyperthreaded related
questions?
Date: Wed, 23 Mar 2005 18:37:16 +1100
Arun Srinivas wrote:
If the SMT (apart from SMP) support is enabled in the .config file, does
the kernel recogonize the 2 logical processor as 2 logical or 2 physical
processors?
You shouldn't be able to select SMT if SMP is not enabled.
If SMT and SMP is selected, then the scheduler will recognise
the 2 processors as logical ones.
Also, as the hyperthreaded processor may schedule 2 threads in the 2
logical cpu's, and it may not necessarily be form the same process i.e.,
the 2 thread it schedules may be from the same or from the different
process.
Yes.
So, is there any way I can tell the scheduler (assuming I make the
scheduler recogonize my 2 threads..i.e., it knows their pid) to schedule
always my 2 threads @ the same time? How do I go abt it?
Use sched_setaffinity to force each thread onto the particular
CPU. Use sched_setscheduler to acquire a realtime scheduling
policy. Then use mutexes to synchronise your threads so they
run the desired code segment at the same time.
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