Re: Query regarding 2.6.335 RT and Non-RT performance

[gowrishankar <gowrishankar.m@linux.vnet.ibm.com>]

On Wednesday 18 August 2010 03:52 AM, Manikandan Ramachandran wrote:
> I see a scenario where higher priority task is ready to run but lower
> priority IRQ thread is hogging the cpu. Please see the timeline log
> below:
>
>    
Can you try turning on RCU_CPU_STALL_DETECTION to get any trace
which might have hogged the cpu too long. Also make sure that
sirq-rcu is running at little more prio than your high prio task.

Thanks,
Gowri
> GIVE ffff0c1c [Comment: High priority IRQ thread wakes up high
> priority process at jiffy 0xffff0c1c]
> **ffff0c21**##ffff0c21##**ffff0c21**##ffff0c21##**ffff0c21**##ffff0c21##**ffff0c21**##ffff0c21##**ffff0c21**##ffff0c22##**ffff0c22**##ffff0c22##**ffff0c22**##ffff0c22##**ffff0c22**##ffff0c22##**ffff0c22**##ffff0c22##**ffff0c22**##ffff0c22##**ffff0c22**##ffff0c22##**ffff0c22**##ffff0c22##**ffff0c23**##ffff0c23##**ffff0c23**##ffff0c23##**ffff0c23**##ffff0c24##**ffff0c24**##ffff0c24##**ffff0c24**##ffff0c24##
> [Comment: Low priority IDE[ide_intr] handler hogs CPU for almost 3 ms]
> GOTffff0c26 [Comment: High priority task wakes up after 10 ms!!]
>
> I fail to understand why scheduler failed to schedule high priority
> task 10 times in a row. FYI, I have put IDE thread to SCHED_NORMAL
> while high priority thread and task to SCHED_FIFO.
>
>