Messages in this thread | | | From | Vincent Guittot <> | Date | Fri, 25 Apr 2014 09:45:34 +0200 | Subject | Re: [PATCH v4 5/5] sched: ARM: create a dedicated scheduler topology table |
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On 24 April 2014 14:48, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > On 24/04/14 08:30, Vincent Guittot wrote: >> On 23 April 2014 17:26, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: >>> On 23/04/14 15:46, Vincent Guittot wrote: >>>> On 23 April 2014 13:46, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: >>>>> Hi, > > [...] > >> >> More than the flag that is used for the example, it's about the >> cpumask which are inconsistent across CPUs for the same level and the >> build_sched_domain sequence rely on this consistency to build >> sched_group > > Now I'm lost here. I thought so far that by specifying different cpu > masks per CPU in an sd level, we get the sd level folding functionality > in sd degenerate? > > We discussed this here for an example on TC2 for the GMC level: > https://lkml.org/lkml/2014/3/21/126 > > Back than I had > CPU0: cpu_corepower_mask=0-1 > CPU2: cpu_corepower_mask=2 > so for GMC level the cpumasks are inconsistent across CPUs and it worked.
The example above is consistent because CPU2 mask and CPU0 mask are fully exclusive
so CPU0: cpu_corepower_mask=0-1 CPU2: cpu_corepower_mask=2 are consistent
CPU0: cpu_corepower_mask=0-2 CPU2: cpu_corepower_mask=0-2 are also consistent
but
CPU0: cpu_corepower_mask=0-1 CPU2: cpu_corepower_mask=0-2 are not consistent
and your example uses the last configuration
To be more precise, the rule above applies on default SDT definition but the flag SD_OVERLAP enables such kind of overlap between group. Have you tried it ?
Vincent
> > The header of '[PATCH v4 1/5] sched: rework of sched_domain topology > definition' mentions only the requirement "Then, each level must be a > subset on the next one" and this one I haven't broken w/ my > GMC/MC/GDIE/DIE set-up. > > Do I miss something else here? > >> >>> Essentially what I want to do is bind an SD_SHARE_*FOO* flag to the GDIE >>> related sd's of CPU2/3/4 and not to the DIE related sd's of CPU0/1. >>> >>> I thought so far that I can achieve that by getting rid of GDIE sd level >>> for CPU0/1 simply by choosing the cpu_foo_mask() function in such a way >>> that it returns the same cpu mask as its child sd level (MC) and of DIE >>> sd level for CPU2/3/4 because it returns the same cpu mask as its child >>> sd level (GDIE) related cpu mask function. This will let sd degenerate >>> do it's job of folding sd levels which it does. The only problem I have >>> is that the groups are not created correctly any more. >>> >>> I don't see right now how the flag SD_SHARE_FOO affects the code in >>> get_group()/build_sched_groups(). >>> >>> Think of SD_SHARE_FOO of something I would like to have for all sd's of >>> CPU's of cluster 1 (CPU2/3/4) and not on cluster 0 (CPU0/1) in the sd >>> level where each CPU sees two groups (group0 containing CPU0/1 and >>> group1 containing CPU2/3/4 or vice versa) (GDIE/DIE) . >> >> I'm not sure that's it's feasible because it's not possible from a >> topology pov to have different flags if the span include all cpus. >> Could you give us more details about what you want to achieve with >> this flag ? > > IMHO, the flag is not important for this discussion. OTHA, information > like you can't use sd degenerate functionality to fold adjacent sd > levels (GFOO/FOO) on sd level which span all CPUs would be. I want to > make sure we understand what are the limitations to use folding of > adjacent sd levels based on per-cpu differences in the return value of > cpu_mask functions. > > -- Dietmar > > [...] >
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