802103 - Breakpad stackwalking optimization: do symbol lookup directly from native debug symbols

Status: RESOLVED FIXED

(Toolkit :: Crash Reporting, defect)

Description

[(not currently active) Ted Mielczarek]

Currently Julian's patch for doing SPS unwinding using Breakpad is using the existing Breakpad symbol dumping classes to construct a symbol file in memory, and then using the existing symbol-parsing classes to built in-memory data structures that are used for unwinding.

This is pretty wasteful. If we implemented a new subclass of SourceLineResolverInterface that used the DWARF parsing classes directly to build its in-memory data structures, we could skip the serialization and parsing steps.

This is a fairly big chunk of the time spent running the unwinder, but it's also a fixed cost in that there's one symbol file per module and they only need to get loaded once.

Comment 1

[(not currently active) Ted Mielczarek]

I talked to Julian about this, but I'll update the bug as well. I implemented a Breakpad class to do this:
http://hg.mozilla.org/users/tmielczarek_mozilla.com/breakpad-local-symbols/

This implements LocalDebugInfoSymbolizer, which can be passed to MinidumpProcessor or a Stackwalker subclass directly and handles loading debug info from local libraries and feeding it to the Stackwalker. (There's also a minidump_stackwalk copy in that repo that uses it which I used for testing.) I've got patches in my mq that hook this up on top of Julian's patch in bug 779291, it all seems to work.

Comment 2

[(not currently active) Ted Mielczarek]

Julian rolled this into his patch in bug 779291, we'll track it there.