This is a living document. Everything in this document is made in good faith of being accurate, but like I just said; we don't yet know everything about what's going on.
On March 29th, 2024, a backdoor was discovered in xz-utils, a suite of software that
GNU parallel is a command line tool for running jobs in parallel.
parallel is awesome and belongs in the toolbox of every programmer. But I found the docs a bit overwhelming at first. Fortunately, you can start being useful with parallel with just a few basic commands.
Let's compare sequential and parallel execution of the same compute-intensive task.
Imagine you have a folder of .wav audio files to convert to .flac:
| Latency Comparison Numbers | |
| -------------------------- | |
| L1 cache reference/hit 1.5 ns 4 cycles | |
| Floating-point add/mult/FMA operation 1.5 ns 4 cycles | |
| L2 cache reference/hit 5 ns 12 ~ 17 cycles | |
| Branch mispredict 6 ns 15 ~ 20 cycles | |
| L3 cache hit (unshared cache line) 16 ns 42 cycles | |
| L3 cache hit (shared line in another core) 25 ns 65 cycles | |
| Mutex lock/unlock 25 ns | |
| L3 cache hit (modified in another core) 29 ns 75 cycles |