On 11/25/2016 04:04 PM, Michael Kerrisk (man-pages) wrote: > Hi Mike, > > On 11/25/2016 02:02 PM, Mike Galbraith wrote: >>> ┌─────────────────────────────────────────────────────┐ >>> │FIXME │ >>> ├─────────────────────────────────────────────────────┤ >>> │How do the nice value of a process and the nice │ >>> │value of an autogroup interact? Which has priority? │ >>> │ │ >>> │It *appears* that the autogroup nice value is used │ >>> │for CPU distribution between task groups, and that │ >>> │the process nice value has no effect there. (I.e., │ >>> │suppose two autogroups each contain a CPU-bound │ >>> │process, with one process having nice==0 and the │ >>> │other having nice==19. It appears that they each │ >>> │get 50% of the CPU.) It appears that the process │ >>> │nice value has effect only with respect to schedul‐ │ >>> │ing relative to other processes in the *same* auto‐ │ >>> │group. Is this correct? │ >>> └─────────────────────────────────────────────────────┘ >> >> Yup, entity nice level affects distribution among peer entities. > > Huh! I only just learned about this via my experiments while > investigating autogroups. > > How long have things been like this? Always? (I don't think > so.) Since the arrival of CFS? Since the arrival of > autogrouping? (I'm guessing not.) Since some other point? > (When?) Okay, things changed sometime after 2.6.31, at least. (Just tested on an old box.) So, presumably with the arrival of either CFS or autogrouping? Next comment certainly applies: > It seems to me that this renders the traditional process > nice pretty much useless. (I bet I'm not the only one who'd > be surprised by the current behavior.) Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
