Here's a status update. Recap: I proposed to create a new library to do fast in process CFI and EXIDX based stack unwinding, so as to be able to profile on tablets and phones with less overhead than using Breakpad.
The library now exists. Tracking bug is 938157. It does CFI unwinding on x86_64-linux and arm-android, EXIDX on arm-android, and stack scanning (as a last resort) on both. Initial integration with SPS has been completed and it produces plausible profiles at least on x86_64-linux. Compared with the best Breakpad based schemes, this library gives easily a factor of 10 cost reduction for CFI unwinding. My best attempts with Breakpad achieved a cost of about 6600 insns/frame on x86_64-linux. The new library comes in at around 470 insns/frame, without much attempt at optimisation. It also facilitates implementation of the the kind of space-saving techniques documented in https://blog.mozilla.org/jseward/2013/09/03/how-compactly-can-cfiexidx-stack-unwinding-info-be-represented/ J _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
