Re: [Libunwind-devel] [PATCH 0/1] Fast back-trace for x86_64 for only collecting the call stack

[Arun Sharma]

On Wed, May 26, 2010 at 9:48 AM, Lassi Tuura <address@hidden> wrote:

Hi Lassi,

> Hi Arun,
>
>> I'm a bit behind on libunwind related emails/patches, but hope to look
>> at your patch in more detail in the next week or so.
>
> Thanks. There's no great urgency, but obviously if we can avoid a patch,
> it's better for us.
>

Paul and I looked into this some more.

What do you think about hiding the API details behind the backtrace()
implementation in

src/mi/backtrace.c

It could attempt a fast backtrace and then fallback to a slower, but
more general backtrace.

It may make sense to expose backtrace_{fast,slow} for users who want
more control over which implementation gets called.

Paul did some profiling of this code a few months ago and noticed that
memcpy and unw_init_local() showed up high. Is it possible to avoid
them? Perhaps unw_init_local() could be made cheaper by initializing
only the subset of the state necessary for backtrace_fast().

 -Arun