Adding CPU affinity in a 24-core build machine made builds take longer
47 points by val
47 points by val
Huh, my toots are ending up here now. Hello over here!
On Linux if you run a single process sometimes it'll start migrating across all cores in turn. IIUC this is done to balance load, but I always thought this to be wasteful when all other cores are idle and there is no "other load" to balance with. But the improved cooling balance is interesting.
"sometimes"? I thought it's basically guaranteed unless you're running with nohz. If you look at the log of context switches, there's typically a wave going through all the cores and will bump the single process. Even more jumpy if you irqbalance...
It’s a hilarious nth-order effect as long as you’re not the one who has to debug the regression.
I'm really like to hear the entire debugging story from the start to how you figured out it was thermal throttling.