linux-kernel - Re: Attaching a process to cgroups

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Date:	Thu, 26 Jul 2012 17:02:22 +0400
From:	Alexey Vlasov <renton@...ton.name>
To:	Mike Galbraith <efault@....de>
Cc:	linux-kernel@...r.kernel.org, paulmck@...ux.vnet.ibm.com
Subject: Re: Attaching a process to cgroups

On Wed, Jul 25, 2012 at 03:57:47PM +0200, Mike Galbraith wrote:
> 
> I'd profile it with perf, and expect to find a large pile of cycles.

I did it the as following:
# perf stat cat /proc/self/cgroup 

4:blkio:/
3:devices:/
2:memory:/
1:cpuacct:/

 Performance counter stats for 'cat /proc/self/cgroup':

          0.472513 task-clock                #    0.000 CPUs utilized          
                 1 context-switches          #    0.002 M/sec                  
                 1 CPU-migrations            #    0.002 M/sec                  
               169 page-faults               #    0.358 M/sec                  
           1111521 cycles                    #    2.352 GHz                    
            784737 stalled-cycles-frontend   #   70.60% frontend cycles idle   
            445520 stalled-cycles-backend    #   40.08% backend  cycles idle   
            576622 instructions              #    0.52  insns per cycle        
                                             #    1.36  stalled cycles per insn
            120032 branches                  #  254.029 M/sec                  
              6577 branch-misses             #    5.48% of all branches        

       9.114631804 seconds time elapsed

# perf report --sort comm,dso
Kernel address maps (/proc/{kallsyms,modules}) were restricted.

Check /proc/sys/kernel/kptr_restrict before running 'perf record'.

If some relocation was applied (e.g. kexec) symbols may be misresolved.

Samples in kernel modules can't be resolved as well.

# ========
# captured on: Thu Jul 26 16:23:06 2012
# hostname : l24
# os release : 3.3.3-1gb-c-s-m
# perf version : 3.2
# arch : x86_64
# nrcpus online : 24
# nrcpus avail : 24
# cpudesc : Intel(R) Xeon(R) CPU E5645 @ 2.40GHz
# total memory : 74181032 kB
# cmdline : /usr/sbin/perf record cat /proc/self/cgroup 
# event : name = cycles, type = 0, config = 0x0, config1 = 0x0, config2 = 0x0, excl_usr = 0, excl_kern = 0, id = { 1758, 1759, 1760, 1761, 1762, 1763, 1764, 1765, 1766, 1767, 1768, 1769, 1770, 1771, 1772, 1773, 1774, 1775, 1776, 1777, 1778, 1779, 1780, 1781 }
# HEADER_CPU_TOPOLOGY info available, use -I to display
# HEADER_NUMA_TOPOLOGY info available, use -I to display
# ========
#
# Events: 21  cycles
#
# Overhead  Command      Shared Object
# ........  .......  .................
#
   100.00%      cat  [kernel.kallsyms]

but I don't know what next unfortunately.

I also checked the same thing on the other server with the 2.6.37 kernel,
there' some thousands cgroups too, and it somehow works there immediately.

-- 
Alexey Vlasov
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