On Fri, 2016-11-25 at 16:04 +0100, Michael Kerrisk (man-pages) 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?) Always. Before CFS there just were no non-peers :) > 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.) Yup, group scheduling is not a single edged sword, those don't exist. Box wide nice loss is not the only thing that can bite you, fairness, whether group or task oriented cuts both ways. -Mike -- 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
