Here's a flame graph of my Opera Helper CPU time, including both kernel and user-level stacks (kernel is above the grey separators):

http://www.brendangregg.com/FlameGraphs/cpu-opera-helper.svg

The 6 towers you see are for each of the 6 Opera Helper processes.

For background on flame graphs:

http://www.brendangregg.com/FlameGraphs/cpuflamegraphs.html

This particular flame graph was generated using:

$ sudo bash
# dtrace -x ustackframes=200 -n 'profile-199 /arg0 && execname == "Opera Helper"/ { @k[stack(), ustack()] = count(); } profile-199 /!arg0 && execname == "Opera Helper"/ { @u[ustack()] = count(); } tick-30s { exit(0); } END { printa("%k%@d\n", @u); printa("%k-%k%@d\n", @k);  }' -o out.operahelper
# cat out.operahelper | ../FlameGraph/stackcollapse.pl | ../FlameGraph/flamegraph.pl --title "Opera Helper Flame Graph" > out.operahelper.svg

With the flame graph software from: https://github.com/brendangregg/FlameGraph

Hope that helps.

On Opera 21, my 8 CPU macbook is running hot, with 6 CPUs pegged by Opera Helper. I'm not really doing anything exotic, other than having many tabs open (around 100).

Here's "top -o cpu":

PID    COMMAND      %CPU  TIME     #TH   #WQ  #PORT #MREG MEM    RPRVT
49635- Opera Helper 101.0 08:40.76 13/1  1    152   358   22M    18M
49677- Opera Helper 100.9 08:40.10 13/1  1    149   259   22M    17M
49668- Opera Helper 100.8 08:39.71 13/1  1    149   305   56M    52M
49646- Opera Helper 100.7 08:43.29 13/1  1    152   403   45M    40M
49676- Opera Helper 100.6 08:40.08 13/1  1    149   258   21M    17M
49675- Opera Helper 100.4 08:40.59 13/1  1    150   259   22M    17M

Using DTrace to profile stacks, shows the hottest includes:

          libsystem_kernel.dylib`_kernelrpc_mach_port_insert_member_trap+0xa
          CoreFoundation`__CFRunLoopRun+0x4e1
          CoreFoundation`CFRunLoopRunSpecific+0x18a
          CoreFoundation`CFRunLoopRunInMode+0x7b
          HIToolbox`RunCurrentEventLoopInMode+0x103
          HIToolbox`ReceiveNextEventCommon+0x20e
          HIToolbox`_BlockUntilNextEventMatchingListInModeWithFilter+0x5c
          AppKit`_DPSNextEvent+0x642
          AppKit`-[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:]+0x77
          AppKit`-[NSApplication run]+0x2d7
          Opera Framework`0x0015bb80+0x14b
          Opera Framework`0x0015b580+0x5c
          Opera Framework`0x0019a390+0x21
          Opera Framework`0x001af2f0+0x41
          Opera Framework`0x0019a140+0x1a
          Opera Framework`0x02c38c70+0x6c0
          Opera Framework`0x001e2d20+0xb3
          Opera Framework`0x001e38d0+0x7f
          Opera Framework`0x001e2c00+0x40
          Opera Framework`ContentMain+0x36
          Opera Helper`0x000cef40+0x35
          Opera Helper`0xd

The Opera Framework symbols are stripped, but I hope the other frames provide a clue.