From mboxrd@z Thu Jan  1 00:00:00 1970
From: M Kelly <mark.kelly@lexisnexis.com>
Subject: Re: =?utf-8?b?c3Bpbl9sb2Nr?= cause ?
Date: Wed, 1 Jun 2016 18:49:01 +0000 (UTC)
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Arnaldo Carvalho de Melo <acme <at> kernel.org> writes:

> No need for DWARF if you want to know what leads to the spinlock just up
> to the syscall layer or if your userland components have frame pointers.

Hi,

ok, I rebuilt our app using -fno-omit-frame-pointer 
and did the perf record -g and when looking at the 
report output I now see:

    40.90%  thorslave_mytho  [kernel.kallsyms]                   [k] _spin_lock                                                                       
            |
            --- _spin_lock
               |          
               |--49.11%-- futex_wake
               |          do_futex
               |          sys_futex
               |          system_call_fastpath
               |          __lll_unlock_wake
               |          |          
               |          |--99.81%-- CKeyCursor::gtEqual(char const*, char*, bool)
               |          |          _ZN16CKeyLevelManager7_lookupEbj.constprop.100
               |
               |--44.31%-- futex_wait_setup
               |          futex_wait
               |          do_futex
               |          sys_futex
               |          system_call_fastpath
               |          __lll_lock_wait
               |          |          
               |          |--99.83%-- CKeyCursor::gtEqual(char const*, char*, bool)
               |          |          _ZN16CKeyLevelManager7_lookupEbj.constprop.100
               |
               |--5.46%-- task_rq_lock
               |          try_to_wake_up
               |          |          
               |          |--99.98%-- wake_up_state
               |          |          wake_futex
               |          |          futex_wake
               |          |          do_futex
               |          |          sys_futex
               |          |          system_call_fastpath
               |          |          __lll_unlock_wake
               |          |          |          
               |          |          |--99.75%-- CKeyCursor::gtEqual(char const*, char*, bool)
               |          |          |          _ZN16CKeyLevelManager7_lookupEbj.constprop.100
               |          
               |--0.73%-- try_to_wake_up
               |          |          
               |          |--99.83%-- wake_up_state
               |          |          wake_futex
               |          |          futex_wake
               |          |          do_futex
               |          |          sys_futex
               |          |          system_call_fastpath
               |          |          __lll_unlock_wake
               |          |          |          
               |          |          |--99.88%-- CKeyCursor::gtEqual(char const*, char*, bool)
               |          |          |          _ZN16CKeyLevelManager7_lookupEbj.constprop.100

So that is helpful.  
I do not understand the system_call_fastpath->futex->_spin_lock part yet, 
but that is a separate issue!

thanks so much,
mark