On Wed, Mar 15, 2017 at 5:04 AM, Patrick Bellasi <[email protected]> wrote: > Few comments inline, otherwise LGTM.
Ok, I'll take that as an Acked-by with the following comment addressed if that's Ok with you. > > On 10-Mar 12:47, Joel Fernandes wrote: >> This patch rewrites comments related task priorities and CPU usage >> along with an example to show how it works. >> >> Cc: Juri Lelli <[email protected]> >> Cc: Patrick Bellasi <[email protected]> >> Cc: Dietmar Eggemann <[email protected]> >> Cc: Peter Zijlstra <[email protected]> >> Cc: Ingo Molnar <[email protected]> >> Signed-off-by: Joel Fernandes <[email protected]> >> --- >> kernel/sched/core.c | 27 +++++++++++++++++++-------- >> 1 file changed, 19 insertions(+), 8 deletions(-) >> >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >> index c56fb57f2991..2175bf663f3d 100644 >> --- a/kernel/sched/core.c >> +++ b/kernel/sched/core.c >> @@ -8823,16 +8823,27 @@ void dump_cpu_task(int cpu) >> } >> >> /* >> - * Nice levels are multiplicative, with a gentle 10% change for every >> - * nice level changed. I.e. when a CPU-bound task goes from nice 0 to >> - * nice 1, it will get ~10% less CPU time than another CPU-bound task >> - * that remained on nice 0. >> + * Nice levels are multiplicative, with a gentle 10% relative change >> + * for every nice level changed. I.e. if there were 2 CPU-bound tasks >> + * of equal nice value and one of them goes from a nice level of 0 to 1 >> + * then the task at nice level 1 will get ~5% less CPU time than before >> + * the change and the task that remained at nice level 0 will get ~5% >> + * more CPU time. >> * >> * The "10% effect" is relative and cumulative: from _any_ nice level, >> - * if you go up 1 level, it's -10% CPU usage, if you go down 1 level >> - * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25. >> - * If a task goes up by ~10% and another task goes down by ~10% then >> - * the relative distance between them is ~25%.) >> + * if you go up 1 level, it's -10% relative CPU usage, if you go down >> + * by 1 level it's +10% CPU usage. > ^ > relative >> + * To achieve that, we use a multiplier of 1.25. > > > The following sentence: > >> + * If a task goes up by ~5% and another task goes down by ~5% >> + * then the relative distance between their weights is ~25% as shown >> + * in the following example: > > is still confusing to me, mainly because we are mixing the "shares > percentage" with the CPU usage percentage. > > What about this: > > If two tasks have a 25% relative distance between their weights > then they will get a 10% difference in CPU usage as shown in the > following example. I agree your statement is clearer and I will use it in the repost. J.
