It started with ssh using unreasonably much cpu which interfered with benchmarks. Then profiling showed that cpu time being spent in lzma, without being attributable to anything. And he remembered earlier valgrind issues. These valgrind issues only came up because he set some build flag he doesn’t even remember anymore why it is set. On top he ran all of this on debian unstable to catch (unrelated) issues early. Any of these factors missing, he wouldn’t have caught it. All of this is so nuts.
Don’t forget all of this was discovered because ssh was running 0.5 seconds slower
Half a second is a really, really long time.
Technically that wasn’t the initial entrypoint, paraphrasing from https://mastodon.social/@AndresFreundTec/112180406142695845 :
It started with ssh using unreasonably much cpu which interfered with benchmarks. Then profiling showed that cpu time being spent in lzma, without being attributable to anything. And he remembered earlier valgrind issues. These valgrind issues only came up because he set some build flag he doesn’t even remember anymore why it is set. On top he ran all of this on debian unstable to catch (unrelated) issues early. Any of these factors missing, he wouldn’t have caught it. All of this is so nuts.
Postgres sort of saved the day
RIP Simon Riggs
https://www.postgresql.org/about/news/remembering-simon-riggs-2830/
Is that from the Microsoft engineer or did he start from this observation?