Luke Kasz lukekasz

MiniPerf

Example of how to capture CPU counters with ETW on Windows, perf on Linux or kperf on Apple.

Using ETW needs somewhat recently updated Windows 10 or 11. Not sure about exact version.

Currently tested on:

etw on Qualcomm Snapdragon X Elite, Windows 11, arm64
etw on AMD Zen 3, Windows 11 (with virtualization enabled in BIOS)

Perfchat 15 May 2022 Show Notes

News by Denis

AMD enhanced their Performance Monitoring Unit. https://www.phoronix.com/scan.php?page=news_item&px=AMD-Zen-4-IBS-Linux - better logging of L3 cache misses to help Kernel on page caching.
rdpmc - a small C++ header-only library to count CPU level events. https://github.com/rodgarrison/rdpmc - x86 only. More lightweight than PAPI
Tachyum launches their Cloud/AI/HPC chip called Prodigy. https://www.hpcwire.com/off-the-wire/tachyum-launches-prodigy-universal-processor/ - how to run QEMU simulator
Mysterious memset, a blog post about pointer aliasing preventing compiler optimizations. https://vector-of-bool.github.io/2022/05/11/char8-memset.html

General Disussion

Mark's blog post

A traditional table-based DFA implementation looks like this:

uint8_t table[NUM_STATES][256]

uint8_t run(const uint8_t *start, const uint8_t *end, uint8_t state) {
    for (const uint8_t *s = start; s != end; s++)
        state = table[state][*s];
    return state;
}

History

http://jakob.engbloms.se/archives/1554
“Debugging Operating Systems with Time-Traveling Virtual Machines“ 2005. Samuel King, George Dunlap, and Peter Chen, - paper - https://www.usenix.org/legacy/events/usenix05/tech/general/king.html - nice list of example bugs for which reverse debugging work much better than cyclic debugging.
“Framework for Instruction-level Tracing and Analysis of Program Executions“, Virtual Execution Environments (VEE), 2006. Sanjay Bhansali, Wen-Ke Chen, Stuart de Jong, Andrew Edwards, Ron Murray, Milenko Drinic, Darek Mihocka, and Joe Chau,
- iDNA paper - https://www.usenix.org/legacy/events/vee06/full_papers/p154-bhansali.pdf
“Don’t Panic: Reverse Debugging of Kernel Drivers“. 2015. Pavel Dovgalyuk, Denis Dmitriev, and Vladimir Makarov,
- An approach using record-replay of hardware interactions from an OS running inside a Qemu virtual amachine,
Paper - https://dl.acm.org/citation.cfm?doid=2786805.2803179