Re: What helps with stacks?

[Andi Kleen <andi@firstfloor.org>]

Daniel Speyer <dspeyer@gmail.com> writes:

> Hello all,
>
> I'm trying to get stack traces for a bunch of events using perf record and
> having trouble with them getting cut off.  I'm using --callgraph dwarf,
> which helps a little, and I recompiled libc with --fno-omit-frame-pointer,
> which doesn't seem to have helped at all.  Very often, the bottom of the
> stack is in libc, often __epoll_wait_nocancel.  Stacks for
> sched:sched_switch events seem to be worse than cycles or sched:sched_wakeup
> events, but it isn't 100%.  Is there anything else I could try?


If you have a Haswell/Broadwell system and uptodate perf (4.0) you can also
use --call-graph lbr

This uses a new hardware mechanism that can handle many situations
where the old ones failed (but also has some situations where
it has to give up)

-andi


-- 
ak@linux.intel.com -- Speaking for myself only