Ubuntu Wiki

• Launchpad Entry: https://blueprints.launchpad.net/ubuntu-arm/+spec/arm-m-debugging-with-oprofile

• Created: 30/04/10

• Contributors:

• Packages affected: linux-tools, linux, oprofile

• UDS-M slides: uds-m-slides.pdf

Summary

As of Linux 2.6.33, ARMv6 and v7 are supported architectures of the perf-events tools. The objectives of this blueprint are to provide Perf and OProfile support for Ubuntu on ARM and discuss designs for `uncore' events and visualisation tools.

Release Note

Hardware profiling features for ARM platforms using OProfile and Perf-events.

Rationale

x86/AMD64 currently have these features in Ubuntu.

Design

The Kernel support required is already available in upstream repositories and on the mailing lists, so most of the backend work is already complete. However, decisions need to be made regarding:

• Support for `uncore' events. This was discussed on the LKML.

• Graphical tool features and UI. This requires discussion: What do we want to visualise and how do we want to visualise it?

Implementation

To make this functionality available to Ubuntu the following actions need to occur:

• Backport ARM backend Kernel patches to the Ubuntu Kernel sources
• Ensure that supported boards [Babbage and Dove] expose their hardware performance counter capabilities in their BSP code
• Package linux-tools for ARM [may need patches for Thumb-2]

With Perf available, OProfile can be made available `for free' with the following actions:

• Backport Kernel patches to replace the OProfile backend with perf
• Update OProfile userspace tools to recognise Cortex-A9 and SMP platforms

There is scope for lots of future work, that needn't be ARM specific. In particular:

• Support for `uncore' events. These are performance events not associated to a particular CPU, for example events occurring on the bus or in the L2 cache.
• Frontend tools. The current userspace tools for Perf are largely text-based. There is scope for developing a graphical front-end, potentially with realtime capabilities, to make the performance counters easier to use.

UI Changes

TBD