3 ms·

Thanks for the explanation. I confirmed the performance timing different by enabling the dup call. I guess my question is why would synchronize_rcu take many

by dekhn 1y ago

Thanks for the explanation. I confirmed the performance timing different by enabling the dup call. I guess my question is why would synchronize_rcu take many milliseconds (20+) to run. I would expect that to be in the very low milliseconds or less.

altairprime 1y ago
> allocating kernel objects from proper virtual memory makes this easier. Linux currently just allocates kernel objects straight out of the linear mapping of all physical memory I found this to be a key takeaway of reading the full thread: this is, in part, a benchmark of kernel memory allocation approaches, that surfaces an unforeseen difference in FD performance at a mere 256 x 2 allocs. Presumably we’re seeing a test case distilled down from a real world scenario where this slowdown was traced for some reason?
saagarjha 1y ago
That’s how they’re designed; they are intended to complete at some point that’s not soon. There’s an “expedited RCU” which to my understanding tries to get everyone past the barrier as fast as possible by yelling at them but I don’t know if that would be appropriate here.