Re: -fno-omit-frame-pointer

[Alex Elsayed <eternaleye@gmail.com>]

Sage Weil wrote:

> Hey Mark,
> 
> I just watched Brendan Gregg's talk at SCALE (which was extremely good)
> and one of the things he mentioned is the importance of
> -fno-omit-frame-pointer.  I notice we are setting it via do_autogen.sh
> (i.e., for developers) but not in the production builds.  Should we be?
> I think it's important to be able to get meaningful callgraph output from
> production deployments and I suspect there is minimal performance impact.
> 
> http://www.slideshare.net/brendangregg/scale2015-linux-perfprofiling

I personally favor DWARF-based unwinding - for one, on register-starved 
architectures such as 32-bit x86, the frame pointer itself can skew 
performance.

With regard to it inflating instance size, that's something that can be 
mitigated - via split debuginfo (only pull in the ones you actually need), 
compressed debug info (zlib -9 shrinks it a good bit), and semantic 
deduplication/compression with dwz.