http://bugzilla.opensuse.org/show_bug.cgi?id=1107617
http://bugzilla.opensuse.org/show_bug.cgi?id=1107617#c19
--- Comment #19 from Martin Wilck
(In reply to Martin Wilck from comment #16)
Well if you're 100% confident that 2 is the best choice for SLE then fine to use this value.
My recommendation is still 2, with an increased constant minimum (K=32 in comment 0). This would provide more workers in the laptop case, while avoiding sky-rocketing numbers for big systems. "100% confidence" is hard to assert, but I have a pretty high confidence level in this. (In reply to Franck Bui from comment #18)
Well I wouldn't be as categorical because as you know it's pretty hard to find a good value that would please all setups. And 8 doesn't seem too bad for desktops.
Yes, I was exaggerating. He's still far below our value of 64. Doing the math like in comment 0 (again: first column "cpu limit", 2nd column "amount of RAM in GiB above which the CPU limit counts): | new upstream | old upstream | | #CPUs | C=8, K = 10 | C = 2, K = 10 | C = 8, K = 32 | C = 2, K = 32 ------------------------------------------------------------------------- 1 | 16 2 | 10 1.3 | 32 4 | 32 4 2 | 24 3 | 12 1.5 | 32 4 | 32 4 4 | 40 5 | 16 2 | 40 4 | 32 4 8 | 72 9 | 24 3 | 72 4 | 32 4 16 | 136 17 | 40 5 | 136 5 | 40 5 1024 | 8200 1049 |2056 263 | 8200 1049 | 2056 263 Systems with ~1000 CPUs are not rare these days. Looking at the last row, you can see that the worker numbers get quite large with C=8. IMHO much more than 2000 workers can't be healthy on any system, no matter now big. I think that the main mistake is the belief that udev is CPU-intensive, and thus the number of allowed workers has to increase with the number of CPUs. It is not, at probably has never been. It's I/O bound, and sometimes, bound by resources such as locks. This is an argument to scale only weakly with the number of CPUs, and my rationale to suggest a scale factor C = 2 with a higher minimum number (K = 32 or 40). Combined with an absolute maximum of 2048, this would be the formula I find optimal for most scenarios. (In reply to Franck Bui from comment #18)
That said I'm wondering if we shouldn't make the default value configurable at compile time so at least servers would use a lower value (let's say 2)
I doubt that our PMs would like to ship different udev binaries for SLES and SLED. But in general, yes, I'd find it useful to make the parameters of the formula configurable. -- You are receiving this mail because: You are on the CC list for the bug.