Hi there! My name is Aki Saarinen.

Oprofiler is a system-wide profiling tool for Linux that utilizes hardware performance counters in the CPU to provide a wide range of interesting statistics about program execution. Oprofiler is not enabled in the standard Android distribution, but with some modifications, it can be used under Android also.

I was able to run oprofiler under Nexus One and Android 2.2, with one limitation. I could only profile once after a restart, further attempts to start the profiler would not succeed in collecting any data. This limits the usability of oprofiler, but it was enough for my immediate profiling needs. If you manage to fix this issue, let me know.

Compile kernel with support for profiling

Oprofiler needs support in the Linux kernel, and the prebuilt kernel for Nexus One doesn’t include this support. You need to compile your own version of the Android kernel for your device, with profiling support enabled.

You can check what kernel version your phone is currently running from Settings->About Phone. I suggest you try to compile the same version of the kernel that the phone is running as default. A good article about building the kernel and platform for Nexus One is available here. I used kernel version 2.6.32 for my phone with Android Froyo 2.2 (FRG83).

You should use standard kernel configuration tools (“make menuconfig”) to enable the support, but you can compare results with this patch to see you’re enabling the right things (CONFIG_OPROFILE, etc).

In order to keep the kernel small enough (there’s a limitation what can be fit into the phone), I additionally needed to disable ext3 and ext2 support.

Interrupt bug in 2.6.32 kernel for Nexus One

Oprofiler module in 2.6.32 kernel is missing an interrupt for Nexus One CPU. The bug is discussed in the android-platform mailing list and original patch are available here. I also have a mirror of the patch, just in case. Apply the patch, include the kernel with your custom Android 2.2 distribution and start profiling.