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Feature #968

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lttng-modules kernel and user callstack context

Added by Mathieu Desnoyers over 8 years ago. Updated 9 months ago.

Status:
Feedback
Priority:
High
Target version:
-
Start date:
10/25/2015
Due date:
% Done:

0%

Estimated time:

Description

Implementation from Francis Giraldeau reviewed and cleaned up available here:

https://github.com/compudj/lttng-tools-dev/tree/callstack
https://github.com/compudj/lttng-modules-dev/tree/callstack

Documentation and tests are missing.

Actions #1

Updated by Jérémie Galarneau almost 8 years ago

  • Status changed from New to Feedback
  • Target version changed from 2.8 to 2.9
Actions #2

Updated by Erica Bugden 9 months ago

  • Target version deleted (2.9)

Kernel and userspace callstack context fields for kernel events are available in LTTng 2.11. Userspace callstack information is currently only available for x86 32/64 systems.


From: What’s new in LTTng 2.11?

Two new context fields are available for Linux kernel channels:

  • callstack-kernel
  • callstack-user

Thanks to those, you can record the Linux kernel and user call stacks when a kernel event occurs. For example:

lttng enable-event --kernel --syscall open
lttng add-context --kernel --type=callstack-kernel --type=callstack-user

When an open() system call occurs, LTTng attaches the kernel and user call stacks to the recorded event.

  • Note: LTTng cannot always sample the user space call stack reliably. For instance, LTTng cannot sample the call stack of user applications and libraries compiled with the -fomit-frame-pointer option. In such a case, the tracing is not affected, but the sampled user space call stack may only contain the user call stack’s topmost address.
Actions #3

Updated by Erica Bugden 9 months ago

(I'm putting this comment in the same issue for now, but can move to another if that becomes more relevant.)

It would be nice to document the userspace x86 limitation more clearly. I found some mentions of the limitation, but they require digging:

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