linux-kernel - Re: excessive kworker activity when idle. (was Re: vma corruption in today's -git)

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Date:	Wed, 30 Mar 2011 23:55:12 -0400
From:	Dave Jones <davej@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>
Subject: Re: excessive kworker activity when idle. (was Re: vma corruption in
 today's -git)

On Wed, Mar 30, 2011 at 08:37:21PM -0700, Linus Torvalds wrote:
 > You don't see some nice thread description
 > in 'top' any more (like you used to when everybody created their own
 > threads and didn't do the common worker thread thing), and the best
 > approach literally seems to be something like
 > 
 >    perf record -ag sleep 10
 >    perf report
 > 
 > which does tend to show what's going on, but it's still a ridiculous
 > way to this.

I tried that, and wasn't particularly enlightened.

+      6.53%  kworker/1:2  [kernel.kallsyms]  [k] read_hpet            
+      4.83%  kworker/0:0  [kernel.kallsyms]  [k] read_hpet           
+      4.28%  kworker/0:0  [kernel.kallsyms]  [k] arch_local_irq_restore 
+      4.03%  kworker/1:2  [kernel.kallsyms]  [k] arch_local_irq_restore  
+      3.10%  kworker/0:0  [kernel.kallsyms]  [k] do_raw_spin_trylock      
+      2.88%  kworker/1:2  [kernel.kallsyms]  [k] do_raw_spin_trylock       
+      2.85%  kworker/1:2  [kernel.kallsyms]  [k] debug_locks_off  
+      2.69%  kworker/0:0  [kernel.kallsyms]  [k] debug_locks_off   
+      2.48%  kworker/0:0  [kernel.kallsyms]  [k] lock_release       
+      2.26%  kworker/1:2  [kernel.kallsyms]  [k] lock_release        
+      2.03%  kworker/0:0  [kernel.kallsyms]  [k] lock_acquire         
+      1.88%  kworker/0:0  [kernel.kallsyms]  [k] arch_local_save_flags 
+      1.87%  kworker/1:2  [kernel.kallsyms]  [k] lock_acquire           
+      1.82%  kworker/1:2  [kernel.kallsyms]  [k] arch_local_save_flags 
+      1.81%  kworker/1:2  [kernel.kallsyms]  [k] arch_local_irq_save    
+      1.78%  kworker/0:0  [kernel.kallsyms]  [k] arch_local_irq_save     
+      1.56%  kworker/0:0  [kernel.kallsyms]  [k] lock_acquired            
+      1.53%  kworker/1:2  [kernel.kallsyms]  [k] __lock_acquire            
+      1.51%  kworker/0:0  [kernel.kallsyms]  [k] __lock_acquire             
+      1.29%  kworker/0:0  [kernel.kallsyms]  [k] native_write_msr_safe       
+      1.23%  kworker/1:2  [kernel.kallsyms]  [k] cpu_relax                    
+      1.17%  kworker/1:2  [kernel.kallsyms]  [k] lock_acquired                 
+      1.17%  kworker/0:0  [kernel.kallsyms]  [k] trace_hardirqs_off_caller      
+      1.11%  kworker/1:2  [kernel.kallsyms]  [k] trace_hardirqs_off_caller       
+      1.08%  kworker/1:2  [kernel.kallsyms]  [k] native_write_msr_safe   
+      1.02%  kworker/0:0  [kernel.kallsyms]  [k] _raw_spin_lock_irqsave   
+      0.92%  kworker/0:0  [kernel.kallsyms]  [k] process_one_work          
+      0.87%  kworker/1:2  [kernel.kallsyms]  [k] _raw_spin_lock_irqsave     
+      0.80%  kworker/0:0  [kernel.kallsyms]  [k] flush_to_ldisc       
+      0.76%  kworker/1:2  [kernel.kallsyms]  [k] process_one_work      
+      0.76%  kworker/1:2  [kernel.kallsyms]  [k] flush_to_ldisc         
+      0.72%  kworker/0:0  [kernel.kallsyms]  [k] arch_local_irq_restore  
+      0.71%  kworker/1:2  [kernel.kallsyms]  [k] arch_local_irq_restore   
+      0.64%  kworker/1:2  [kernel.kallsyms]  [k] do_raw_spin_unlock        
+      0.63%  kworker/0:0  [kernel.kallsyms]  [k] perf_event_task_tick       
+      0.61%  kworker/1:2  [kernel.kallsyms]  [k] ktime_get                   
+      0.59%  kworker/0:0  [kernel.kallsyms]  [k] _raw_spin_unlock_irqrestore  

this is what led me to try the other perf methods. the kmem traces were
the only things that really jumped out.

 > (Powertop can also do it, and is probably a better thing to use, I'm
 > just used to "perf record" for other reasons, so..)

Tried that too, here's what it said..

Summary: 0.0 wakeups/second,  0.0 GPU ops/second and 0.0 VFS ops/sec

                Usage       Events/s    Category       Description
            -2147483648 ms/s   0.0        Timer
            -2147483648 ms/s   0.0        kWork
            35151589 ms/s    0.0        Timer
            35151588 ms/s    0.0        Timer
            35151587 ms/s    0.0        Timer
            35151586 ms/s    0.0        Timer
            35151585 ms/s    0.0        Timer
            35151585 ms/s    0.0        Timer
            35151584 ms/s    0.0        Timer
            35151583 ms/s    0.0        Timer
            35151582 ms/s    0.0        Timer
            35151581 ms/s    0.0        Timer
            35151581 ms/s    0.0        Timer
            35151580 ms/s    0.0        Timer

Not exactly helpful.

	Dave

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