On Tue, 18 May 2021 at 17:48, Beata Michalska <beata.michalska@xxxxxxx> wrote: > > On Tue, May 18, 2021 at 05:28:11PM +0200, Vincent Guittot wrote: > > On Tue, 18 May 2021 at 17:09, Beata Michalska <beata.michalska@xxxxxxx> wrote: > > > > > > On Tue, May 18, 2021 at 04:53:09PM +0200, Vincent Guittot wrote: > > > > On Tue, 18 May 2021 at 16:27, Beata Michalska <beata.michalska@xxxxxxx> wrote: > > > > > > > > > > On Tue, May 18, 2021 at 03:39:27PM +0200, Vincent Guittot wrote: > > > > > > On Mon, 17 May 2021 at 10:24, Beata Michalska <beata.michalska@xxxxxxx> wrote: > > > > > > > > > > > > > > Introducing new, complementary to SD_ASYM_CPUCAPACITY, sched_domain > > > > > > > topology flag, to distinguish between shed_domains where any CPU > > > > > > > capacity asymmetry is detected (SD_ASYM_CPUCAPACITY) and ones where > > > > > > > a full range of CPU capacities is visible to all domain members > > > > > > > (SD_ASYM_CPUCAPACITY_FULL). > > > > > > > > > > > > I'm not sure about what you want to detect: > > > > > > > > > > > > Is it a sched_domain level with a full range of cpu capacity, i.e. > > > > > > with at least 1 min capacity and 1 max capacity ? > > > > > > or do you want to get at least 1 cpu of each capacity ? > > > > > That would be at least one CPU of each available capacity within given domain, > > > > > so full -set- of available capacities within a domain. > > > > > > > > Would be good to add the precision. > > > Will do. > > > > > > > > Although I'm not sure if that's the best policy compared to only > > > > getting the range which would be far simpler to implement. > > > > Do you have some topology example ? > > > > > > An example from second patch from the series: > > > > > > DIE [ ] > > > MC [ ][ ] > > > > > > CPU [0] [1] [2] [3] [4] [5] [6] [7] > > > Capacity |.....| |.....| |.....| |.....| > > > L M B B > > > > The one above , which is described in your patchset, works with the range policy > Yeap, but that is just a variation of all the possibilities.... > > > > > > > > Where: > > > arch_scale_cpu_capacity(L) = 512 > > > arch_scale_cpu_capacity(M) = 871 > > > arch_scale_cpu_capacity(B) = 1024 > > > > > > which could also look like: > > > > > > DIE [ ] > > > MC [ ][ ] > > > > > > CPU [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] > > > Capacity |.....| |.....| |.....| |.....| |.....| > > > L M B L B > > > > I know that that HW guys can come with crazy idea but they would > > probably add M instead of L with B in the 2nd cluster as a boost of > > performance at the cost of powering up another "cluster" in which case > > the range policy works as well > > > > > > > > Considering only range would mean loosing the 2 (M) CPUs out of sight > > > for feec in some cases. > > > > Is it realistic ? Considering all the code and complexity added by > > patch 2, will we really use it at the end ? > > > I do completely agree that the first approach was slightly .... blown out of > proportions, but with Peter's idea, the complexity has dropped significantly. > With the range being considered we are back to per domain tracking of available > capacities (min/max), plus additional cycles on comparing capacities. > Unless I fail to see the simplicity of that approach ? With the range, you just have to keep track of one cpumask for min capacity and 1 for max capacity (considering that the absolute max capacity/1024 might not be in the cpumap) instead of tracking all capacity and manipulating/updating a dynamic link list. Then as soon as you have 1 cpu of both masks then you are done. As a 1st glance this seems to be simpler to do. > > --- > BR > B. > > Regards, > > Vincent > > > > > > --- > > > BR. > > > B > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > --- > > > > > BR > > > > > B. > > > > > > > > > > > > > > > > > > > > > > > > > > With the distinction between full and partial CPU capacity asymmetry, > > > > > > > brought in by the newly introduced flag, the scope of the original > > > > > > > SD_ASYM_CPUCAPACITY flag gets shifted, still maintaining the existing > > > > > > > behaviour when one is detected on a given sched domain, allowing > > > > > > > misfit migrations within sched domains that do not observe full range > > > > > > > of CPU capacities but still do have members with different capacity > > > > > > > values. It loses though it's meaning when it comes to the lowest CPU > > > > > > > asymmetry sched_domain level per-cpu pointer, which is to be now > > > > > > > denoted by SD_ASYM_CPUCAPACITY_FULL flag. > > > > > > > > > > > > > > Signed-off-by: Beata Michalska <beata.michalska@xxxxxxx> > > > > > > > Reviewed-by: Valentin Schneider <valentin.schneider@xxxxxxx> > > > > > > > --- > > > > > > > include/linux/sched/sd_flags.h | 10 ++++++++++ > > > > > > > 1 file changed, 10 insertions(+) > > > > > > > > > > > > > > diff --git a/include/linux/sched/sd_flags.h b/include/linux/sched/sd_flags.h > > > > > > > index 34b21e9..57bde66 100644 > > > > > > > --- a/include/linux/sched/sd_flags.h > > > > > > > +++ b/include/linux/sched/sd_flags.h > > > > > > > @@ -91,6 +91,16 @@ SD_FLAG(SD_WAKE_AFFINE, SDF_SHARED_CHILD) > > > > > > > SD_FLAG(SD_ASYM_CPUCAPACITY, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS) > > > > > > > > > > > > > > /* > > > > > > > + * Domain members have different CPU capacities spanning all unique CPU > > > > > > > + * capacity values. > > > > > > > + * > > > > > > > + * SHARED_PARENT: Set from the topmost domain down to the first domain where > > > > > > > + * all available CPU capacities are visible > > > > > > > + * NEEDS_GROUPS: Per-CPU capacity is asymmetric between groups. > > > > > > > + */ > > > > > > > +SD_FLAG(SD_ASYM_CPUCAPACITY_FULL, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS) > > > > > > > + > > > > > > > +/* > > > > > > > * Domain members share CPU capacity (i.e. SMT) > > > > > > > * > > > > > > > * SHARED_CHILD: Set from the base domain up until spanned CPUs no longer share > > > > > > > -- > > > > > > > 2.7.4 > > > > > > >
