joyent/node — Issue #2852: dtrace ustack helper improvements
Author: davepacheco
Created: 2012-03-01 19:45:05+00:00
State: open

There are a few issues with the current DTrace ustack helper:

* It sometimes produces incomplete output. Instead of saying "func at file.js position 123", it will say " at position 123". This turned out to be a result of catching V8 during GC, where it's twiddled the last bits of various pointers, causing the helper to read the wrong memory.
* There are certain types of internal frames where there's a Code object rather than a JSFunction object on the stack. Currently, the helper simply doesn't translate it at all, leaving you with a hex address. This interferes with stack coalescing (as via Brendan Gregg's FlameGraph tools) because you see varying hex addresses in the stack, so they appear different even though they're pretty much indistinguishable to Node programmers.

I've already got fixes for these. There's a pull request coming shortly.